This study examined the effect of different negative pressures and soil textures on water and salt movement to improve the efficiency of negative pressure irrigation(NPI).Four soil textures of varying fineness(Loamy S...This study examined the effect of different negative pressures and soil textures on water and salt movement to improve the efficiency of negative pressure irrigation(NPI).Four soil textures of varying fineness(Loamy Sand,Loam,Silty Loam,and Sandy Loam) and three negative pressure values(0,-5,and-10 kPa) were used.As irrigation time increased,wetting front movement speeds decreased,and as negative pressure increased,wetting front size decreased.Coarse soils had the smallest wetting front under greater negative pressure.Next,water infiltration rate decreased as irrigation time increased,and coarse soils had the lowest average infiltration rate under greater negative pressure.Finally,salt content increased with distance from the irrigation emitter and with increased negative pressure.Further,coarse soils were found to have decreased desalination under greater negative pressure.Thus,soil texture has a strong effect on NPI efficiency.However,by adjusting pressure values in accordance with soil texture,soil water content can be controlled and maintained.These findings are important to the improvement of NPI systems,increasing their practicality for agricultural use.展开更多
A field experiment study was conducted in Bashang Plateau in North China in 2008 to determine the effect of three first cutting dates on the growth and water use efficiency(WUE) of Siberian wildrye(Elymus sibiricus L....A field experiment study was conducted in Bashang Plateau in North China in 2008 to determine the effect of three first cutting dates on the growth and water use efficiency(WUE) of Siberian wildrye(Elymus sibiricus L.) in the agropastoral ecotone of North China(APENC).The experiment was conducted in a split plot design with three replications with water supply regime as the main plot treatment and first cutting date as the subplot treatment.Two water supply regimes were used,which included rain-fed treatment as control(CK) and a single irrigation and straw mulch treatment(W).Three first cutting date treatments were conducted at early heading stage on July 1(E),at late heading stage on July 12(L),and at flowering stage on July 27(F),respectively.The results showed that the forage yield and WUE were the lowest at early heading stage harvest,while the highest at flowering stage either in CK or W treatment.Under combined CK and W treatments,average forage yields of the F subplots were 2 900 and 6 703 kg ha-1,and the values of WUE were 0.82 and 2.28 kg m-3,respectively.Under the CK treatment,forage yields of the E and L subplots were 43.8 and 41.9% lower than the F subplots,and their values of WUE were 46.2 and 50.3% lower than F,respectively.Under the W treatment,the forage yields of the E and L subplots were 74.9 and 61.6% lower,and their values of WUE were 78.1 and 63.3% lower,respectively,as compared with F subplots.Therefore,earlier first cutting did not increase the regrowth of Siberian wildrye and improve the mismatch between rainy season and the period of high growth potential of the grass in the semiarid APENC.展开更多
Some soil properties were studied in relation soil aggregate along a climatologically region and different crop land use in the Northeast of Sulaimani City/Kurdistan Region of Iraq. Five locations were selected along ...Some soil properties were studied in relation soil aggregate along a climatologically region and different crop land use in the Northeast of Sulaimani City/Kurdistan Region of Iraq. Five locations were selected along these regions ranging from semiarid to sub-humid climatologically conditions. The soil physical, chemical properties, aggregate stability and size distribution were analyzed. A mean-weight-diameter (MWD) value was determined on 5 soils, which was the sum of the percentage of soil on each sieve (6, 3, 1.5, 0.75, 0.375 and 0.125 mm). The results of the measurements could evaluated with linear correlation coefficients for the relationships between aggregate stability (MWD) and soil physical and chemical properties of the different crop land use. The correlation coefficient for the relationship between aggregate stability and organic matter was highly significant (P < 0.0l%) which is in agreement with the findings of [1]. Generally large aggregates (large 6, 3, 3 - 1.5 mm) were present in highest proportions in the most semiarid of the studied areas. Aggregates 0.75 - 0.125 mm were positively correlated to fine, very fine sand and silt fractions and to organic matter. Stability of aggregates showed a positive correlation with clay content and organic matter content, while the carbonate content was strongly correlated with aggregate stability. The land use history affecting soil overlaps the pattern of climatological situations and cultivated crop lands and has to be taken into account. Aggregate size distribution and stability can be used as indicator of soil conservation and productivity.展开更多
响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续...响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续气流包围方法被用来在稻田测量氨挥发。通过氨挥发的全部的 N 损失通常与 N 申请率，和申请评估的二更高的 N 增加了(300 和 350 kg N 哈 ? 1 ) 证明 N 的更高的比率通过氨挥发输了到应用 N。由在全部米饭期间，生长上演的氨挥发的全部的氨损失从 9.0% ～ 16.7% 应用 N 。增加申请率通常减少了在到在植物的 N 的种子的 N 的比率。为所有 N 处理，氮肥利用效率从 30.9% ～ 45.9%。有最高的 N 率的剩余 N 导致了米饭植物，氮肥利用的减少的率，和减少的米饭收益的住宿。从这个实验计算，最节俭的 N 化肥申请率是 227 kg 哈 ? 1 为在泰胡·莱克区域的水稻土的类型。然而，推荐适当 N 化肥申请率以便植物生长被提高，氨损失被减少能改进大米的 N 利用效率。展开更多
Innovative measure is a urgent requirement for managing the huge volume of municipal sewage sludge. The hydrothermal carbonation(HTC) shows some potential advantages for using hydrochar as a soil conditioner. The aim ...Innovative measure is a urgent requirement for managing the huge volume of municipal sewage sludge. The hydrothermal carbonation(HTC) shows some potential advantages for using hydrochar as a soil conditioner. The aim of this work was to investigate the properties of hydrochars, by means of the HTC of municipal sewage sludge under different temperatures(190 and 260°C) and reaction hours(1, 6, 12, 18 and 24 h). The HTC led to the decreases of N, O and H contents by more than 54.6, 37.9 and 10.0%, respectively, and slight changes of C content. The Py-GC-MS analysis showed that a large proportion of fatty acids, in particular hexadecanoic acid, transferred into alkenes, olefins and aromatic compounds. The 13C-NMR and fourier transform infrared spectra(FTIR) confirmed the transformation and changes in chemical structure in which hydrochar contained lower oxygen-containing organic C of O-alkyl, carboxylic and carbonyl C and aliphaticity, but higher aromatic C and aromaticity. The rich hydrophobic functions induced in high positive charges in the charred sludge. The HTC facilitated the pore structure development, proved by higher specific surface area and specific pore volume, with a maximum of 17.30 and 0.83 cm3 g-1, respectively. The availabilities of N, P and K markedly reduced during HTC treatment. The activities of most heavy metals were depressed though they accumulated in the hydrochar. Further work is required to investigate the values and risk of the charred sludge amended to soil.展开更多
Tillage greatly influences the aggregation and stability of soil aggregates. This study investigated the effects of conservation tillage on soil aggregate characteristics. During a four-year study period (2001-2005), ...Tillage greatly influences the aggregation and stability of soil aggregates. This study investigated the effects of conservation tillage on soil aggregate characteristics. During a four-year study period (2001-2005), soils were sampled from no-tillage (NT), rotary tillage (RT), and conventional tillage (moldboard tillage, CT) plots at the Luancheng Agriculture and Ecology Experimental Station in Hebei Province, China, and the amount, size distribution, and fractal dimension of the aggregates were examined by dry and wet sieving methods. The results indicated that NT significantly increased the topsoil (0-5 cm) bulk density (BD), while RT maintained a lower BD as CT. Dry sieving results showed that NT had higher macro-aggregate content (R0.25), and a larger mean weight diameter (MWD) and geometric mean diameter (GMD) than other treatments in the 0-10 cm layer, while RT showed no difference from CT. In wet sieving, results showed that most of the aggregates were unstable, and the MWD and GMD of water-table aggregates showed the trend of NT > RT > CT. At 0-5 cm layer, the fractal dimension (D) of water-stable aggregates under NT was lower than it was under RT and CT. At 5-10 cm, RT yielded the highest D, and showed stability. After four years, NT increased the aggregation and the stability of soil aggregates; while due to intense disturbance, the aggregation and stability of the upper layer (0-10 cm) under RT and CT decreased.展开更多
The structure of the "black soil" in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage (CT) practices. In this study, micromorphological observation an...The structure of the "black soil" in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage (CT) practices. In this study, micromorphological observation and image analysis of soil thin sections were conducted to evaluate the impacts of 21 years (1986-2007) of no tillage (NT) on soil structure as compared to CT in an experiment near Gongzhuling City, Jilin Province. Soil organic matter (SOM), wet aggregate stability and saturated hydraulic conductivity (Ks) were also analyzed. Total SOM was not significantly affected by tillage systems, but fresher SOM was observed in the surface layer under NT. The aggregates under NT showed different hierarchies in the form of crumbs, and the mean weight diameter (MWD) of NT was significant higher than that of CT in the surface layer. Platy and blocky aggregates were frequently observed in the lower layers under CT practice. The compound pore structure with intertwined intra-and interaggregates pores under NT was well developed in a layer from 0-5 cm to 20-25 cm. While under CT system, more inter-aggregate pores and fewer intraaggregate pores were observed, and planes and channels were frequently found in the 20-25 cm layer, where macroporosity decreased significantly and a plow pan was evident. The Ks values of NT were significantly lower at 0-5 cm but significantly higher at 20-25 cm compared with CT, which showed the same trend with macroporosity. These results confirmed that long-term CT practice fragmented the tillage layer soil and compacted the lower layer soil and formed a plow pan. While long-term NT practice in the black soil region favored soil aggregation and a stable porous soil structure was formed, which are important to the water infiltration and prevent soil erosion.展开更多
Since industrial revolution,the atmospheric CO2concentration has kept a continuous increase by more than 2.2 ppm yr-1,and approaches to almost 400 ppm at present(Jouzel 2012).China has become the largest country of gr...Since industrial revolution,the atmospheric CO2concentration has kept a continuous increase by more than 2.2 ppm yr-1,and approaches to almost 400 ppm at present(Jouzel 2012).China has become the largest country of greenhouse gas emission(GHG),and confronts with great challenge to mitigate GHG.Soil is widely considered not only as an important carbon sink in terrestrial ecosystem,but greenhouse gas resource as well.It is estimated that the soils展开更多
Land use changes from natural ecosystems into managed ecosystems resulted in negative impact on soil structure and quality. The purpose of this study was to determine the influences of different land-use types on phys...Land use changes from natural ecosystems into managed ecosystems resulted in negative impact on soil structure and quality. The purpose of this study was to determine the influences of different land-use types on physical and chemical properties of soils in Sulaimani governorate. Land use systems including natural forest, pastureland and agriculture were identified. Ten of soil samples were collected from the 0 - 30 cm depth, and some soil physical and chemical properties of soil were determined. The land use alters from forest to agriculture resulting in significant decrease in organic matter, calcium carbonate and soil surface area and with this change, dispersion ratio affected on the physical property. The value of DR was highest in the Zrguezi Gawra cultivated with Cucumber and the lowest value in Dukan is 13%, and correlation coefficient between dispersion DR with sand, silt and bulk density is positive, value is (0.4979, 0.0126 and 0.7536) respectively, and with clay and specific surface area (SSA) the correlation coefficient value is (-0.7281 and -0.4466).展开更多
Rubber is an economically important perennial crop in Myanmar for latex production. As the rubber plantation area increases yearly, the requirement of vigorous rubber seedlings for its establishment plays a central ro...Rubber is an economically important perennial crop in Myanmar for latex production. As the rubber plantation area increases yearly, the requirement of vigorous rubber seedlings for its establishment plays a central role. The success of rubber plantations depends on some farming practices such as using different compost or other materials in the potting soil-medium, varietal selection for stock and scion in the budding process, and fertilizer application methods. The objective of this study was to assess the farmer’s practices in the establishment of rubber nurseries in mostly rubber planted areas in Myanmar. The survey interviewed 60 respondents from three townships in Mon State, namely Mudon, Kyaikmaraw, and Thanbyuzayat. The response data were analyzed through the descriptive method. This survey exposed the potentially active operators (middle age of 30 - 60 years) in rubber nursery production. Local experienced farmers usually raised the budded seedlings with 15 cm × 23 cm polyethylene bag in all study regions. Most farmers selected multi-clonal seed for stock and BPM 24 for scion according to the local market demand and high latex yield. All survey areas used both organic and inorganic fertilizers for nutrient management. Compost is a chief component of growing medium in their nursery production. However, making compost and high demand of the compost were local constraints. Therefore, this survey suggested improving the proper composting method for rubber nursery establishment.展开更多
Protecting and preserving our environmental systems require the ability to understand the spatio-temporal distri- bution of soils, parent material, topography, and land cover as well as the effects of human activities...Protecting and preserving our environmental systems require the ability to understand the spatio-temporal distri- bution of soils, parent material, topography, and land cover as well as the effects of human activities on ecosystems. Space-time modelling of ecosystems in an environmental digital library is essential for visualizing past, present, and future impacts of changes occurring within such landscapes (e.g., shift in land use practices). In this paper, we describe three novel features, spa- tio-temporal indexing, visualization, and geostatistical genre, for the environmental digital library, Environmental Visualization and Geographic Enterprise System (ENVISAGE), currently in progress at the University of Florida.展开更多
The North China Plain(NCP)is a major grain production area in China,but the current winter wheatsummer maize system has resulted in a large water deficit.This water-shortage necessitates the improvement of crop water ...The North China Plain(NCP)is a major grain production area in China,but the current winter wheatsummer maize system has resulted in a large water deficit.This water-shortage necessitates the improvement of crop water productivity in the NCP.A crop water model,AquaCrop,was adopted to investigate yield and water productivity(WP)for rain-fed summer maize on the piedmont of the NCP.The data sets to calibrate and validate the model were obtained from a 3-year(2011–2013)field experiment conducted on the Yanshan piedmont of the NCP.The range of root mean square error(RMSE)between the simulated and measured biomass was 0.67–1.25 t·hm^(–2),and that of relative error(RE)was 9.4%–15.4%,the coefficient of determination(R^(2))ranged from 0.992 to 0.994.The RMSE between the simulated and measured soil water storage at depth of 0–100 cm ranged from 4.09 to 4.39 mm;and RE and R^(2) in the range of 1.07%–1.20%and 0.880–0.997,respectively.The WP as measured by crop yield per unit evapotranspiration was 2.50–2.66 kg·m^(–3).The simulated impact of long-term climate(i.e.,1980–2010)and groundwater depth on crop yield and WP revealed that the higher yield and WP could be obtained in dry years in areas with capillary recharge from groundwater,and much lower values elsewhere.The simulation also suggested that supplementary irrigation in areas without capillary groundwater would not result in groundwater over-tapping since the precipitation can meet the water required by both maize and ecosystem,thus a beneficial outcome for both food and ecosystem security can be assured.展开更多
Transpiration and photosynthesis are two closely related and intercoupled processes that dominate the physiological activities and yield of crops. Therefore, there is a need to study water-carbon coupling modeling at ...Transpiration and photosynthesis are two closely related and intercoupled processes that dominate the physiological activities and yield of crops. Therefore, there is a need to study water-carbon coupling modeling at various scales to increase water use efficiency (WUE). Using a summer maize field in North China as an example, the variations in leaf and canopy photosynthesis and transpiration (or evapotranspiration) were analyzed. The synthetic model of photosynthesis-transpiration based on stomatal behavior (SMPT-SB) was then calibrated and validated at the two scales. The leaf photosynthesis and transpiration, as well as the canopy photosynthesis and evapotranspiration, have a consistent diurnal trend. However, the canopy evapotranspiration is affected more by topsoil moisture content. The regression coefficient between leaf photosynthesis, transpiration, and WUE estimated by the SMPT-SB and the measured values was found to approach 1, with a coefficient of determination of more than 0.74. The relative error between the two sets of values is less than 11%. Therefore, the SMPT-SB could express fairly well leaf photosynthesis, transpiration, and WUE. The estimated canopy-scale photosynthesis by the SMPT-SB is also in good agreement with the measured values. However, this model underestimates the canopy evapotranspiration when the topsoil has high moisture content and therefore overestimates, to a certain extent, the canopy WUE.展开更多
Deep learning and computer vision have become emerging tools for diseased plant phenotyping.Most previous studies focused on image-level disease classification.In this paper,pixel-level phenotypic feature(the distribu...Deep learning and computer vision have become emerging tools for diseased plant phenotyping.Most previous studies focused on image-level disease classification.In this paper,pixel-level phenotypic feature(the distribution of spot)was analyzed by deep learning.Primarily,a diseased leaf dataset was collected and the corresponding pixel-level annotation was contributed.A dataset of apple leaves samples was used for training and optimization.Another set of grape and strawberry leaf samples was used as an extra testing dataset.Then,supervised convolutional neural networks were adopted for semantic segmentation.Moreover,the possibility of weakly supervised models for disease spot segmentation was also explored.Grad-CAM combined with ResNet-50(ResNet-CAM),and that combined with a few-shot pretrained U-Net classifier for weakly supervised leaf spot segmentation(WSLSS),was designed.They were trained using image-level annotations(healthy versus diseased)to reduce the cost of annotation work.Results showed that the supervised DeepLab achieved the best performance(IoU=0.829)on the apple leaf dataset.The weakly supervised WSLSS achieved an IoU of 0.434.When processing the extra testing dataset,WSLSS realized the best IoU of 0.511,which was even higher than fully supervised DeepLab(IoU=0.458).Although there was a certain gap in IoU between the supervised models and weakly supervised ones,WSLSS showed stronger generalization ability than supervised models when processing the disease types not involved in the training procedure.Furthermore,the contributed dataset in this paper could help researchers get a quick start on designing their new segmentation methods in future studies.展开更多
The effect of a machine feeding rate(FR;1,1.5 and 2 Mg/h)and/or three levels of selected fineness degree(FD;3,5 and 7 mm)on machine performance,pellet physical parameters,required energy and production cost of three m...The effect of a machine feeding rate(FR;1,1.5 and 2 Mg/h)and/or three levels of selected fineness degree(FD;3,5 and 7 mm)on machine performance,pellet physical parameters,required energy and production cost of three main types of broilers diets were examined in this experiment.The examined broiler diets were formulated to meet the Ross 308 strain requirements.A complete factorial design(3×3×3)was used to identify the effects of studied factors on the pellet mill machine and pellet production.The obtained results indicated that the pellet mill productivity significantly(p˂0.001)improved through increased pellet mill feeding rate level.In addition,the machine pelleting efficiency was found to be significantly affected by all studied variables and their interactions.While the total power consumption of the machine showed no variations under the impact of the tested factors or with any of their combinations.Regarding the pellet physical quality indices,all broiler diets with all selected FD and lower FR had the maximum durability and bulk density levels.Furthermore,lower feeding rates were associated with higher hardness degrees.The lowest production costs were substantially correlated with high FR and intermediate FD(5 mm).Furthermore,production costs were determined to be reduced in finisher broiler diets under different feeding rates.Moreover,manufacturing costs of finisher broiler meals were observed to decrease in several feeding rates.Overall,these findings indicate the capabilities of producing high-quality pellets and reducing the needed production costs by optimizing feeding rates to 2 Mg/h and 2 mm fineness in broiler diets.展开更多
Land use changes profoundly affect the equilibrium of soil organic carbon(soC)sequestration and greenhouse gas emissions.With the current global climatic changes,it is vital to understand the influence of ecological r...Land use changes profoundly affect the equilibrium of soil organic carbon(soC)sequestration and greenhouse gas emissions.With the current global climatic changes,it is vital to understand the influence of ecological restoration and conservation management on the dynamics of soC under different land uses,especially in erosion-endangered Loess soils.Therefore,we investigated changes in soc through a suit of labile fractions,namely:light fraction organic C(LFOC),heavy fraction organic C(HFOC),coarse particulate organic C(CPOC),fine particulate organic C(FPOC),and dissolved organic C(DOC),from two forests i.e.,Robinia pseudoacacia(RP)and Platycladus orientalis(PO),with different ages,in comparison with farmland(FL).The SOC and STN contents significantly increased over 42 years in the RP forest where the contents of CPOC and FPOC were significantly higher than in the FL.Moreover,total SOC and its labile fractions,in the studied land use types,significantly correlated with soil CacO3,pH,and STN contents,indicating their key roles in SoC sequestration.The results reported here from different vegetation with different ages provide a better understanding of sOC and STN alterations at different stages of vegetation restoration.Our findings suggest that long-term natural vegetation restoration could be an effective approach for SoC sequestration and soil conservation on the Loess soil.展开更多
Biochar is known to ameliorate soil fertility and increase crop yield;however,information regarding its effects on soil chemical and biological properties remains limited.The experiment was conducted to study the shor...Biochar is known to ameliorate soil fertility and increase crop yield;however,information regarding its effects on soil chemical and biological properties remains limited.The experiment was conducted to study the short-term impacts of dif-ferent types of biochar on soil C fractions,enzyme activities,and microbial community structure at depositional and eroded landscape positions at different sampling times[before planting,after planting,and after harvesting of soybean(Glycine max L.)].Three biochar materials,produced from C-optimized gasification of corn(maize,Zea mays L.)stover(CS),pon-derosa pine(Pinus ponderosa Lawson and C.Lawson)wood residue(PW),and switchgrass(Panicum virgatum L.)(SG),and dairy manure(DM)and mixture of dairy manure and pinewood biochar(DMP),were applied at a rate of 10 Mg ha^(−1) to depositional and eroded landscape positions.Data showed that the application of DMP and sole application of DM treat-ments significantly increased the labile C fractions at the depositional and eroded landscapes.The addition of DM and DMP increased the activities ofβ-glucosidase and urease enzymes,and those are involved in C and nitrogen cycling at depositional and eroded landscape positions.There were no significant differences between different biochar materials.However,there was an increase in soil microbial community structure in the DM and DMP treatments at both the landscape positions.In conclusion,our study revealed that DMP and sole application of DM influenced the soil labile C pool,enzyme activities,and microbial community structure at both the landscape positions for different sampling times.展开更多
The applicability, transferability, and scalability of visible/near-infrared(VNIR)-derived soil total carbon(TC) models are still poorly understood. The objectives of this study were to: i) compare models of three mul...The applicability, transferability, and scalability of visible/near-infrared(VNIR)-derived soil total carbon(TC) models are still poorly understood. The objectives of this study were to: i) compare models of three multivariate statistical methods, partial least squares regression(PLSR), support vector machine(SVM), and random forest methods, to predict soil logarithm-transformed TC(logTC) using five fields(local scale) and a pooled(regional-scale) VNIR spectral dataset(a total of 560 TC spectral datasets), ii)assess the model transferability among fields, and iii) evaluate their up-and downscaling behaviors in Florida, USA. The transferability and up-and downscaling of the models were limited by the following factors: i) the spectral data domain, ii) soil attribute domain,iii) methods that describe the internal model structure of VNIR-TC relationships, and iv) environmental domain space of attributes that control soil carbon dynamics. All soil logTC models showed excellent performance based on all three methods with R^2> 0.86,bias < 0.01%, root mean squared error(RMSE) = 0.09%, residual predication deviation(RPD) > 2.70%, and ratio of prediction error to interquartile range(RPIQ) > 4.54. The PLSR method performed substantially better than the SVM method to scale and transfer the TC models. This could be attributed to the tendency of SVM to overfit models, while the asset of the PLSR method was its robustness when the models were validated with independent datasets, transferred, and/or scaled. The upscaled soil TC models performed somewhat better in terms of model fit(R2), RPD, and RPIQ, whereas the downscaled models showed less bias and smaller RMSE based on PLSR. We found no universal trend indicating which of the four limiting factors mentioned above had the most impact that constrained the transferability and scalability of the models. Given that several factors can impinge on the empirically derived soil spectral prediction models, as demonstrated by this study, more focus on their applicability and scalability is needed.展开更多
基金supported by the National High-Tech R&D Program of China (2013AA102901)
文摘This study examined the effect of different negative pressures and soil textures on water and salt movement to improve the efficiency of negative pressure irrigation(NPI).Four soil textures of varying fineness(Loamy Sand,Loam,Silty Loam,and Sandy Loam) and three negative pressure values(0,-5,and-10 kPa) were used.As irrigation time increased,wetting front movement speeds decreased,and as negative pressure increased,wetting front size decreased.Coarse soils had the smallest wetting front under greater negative pressure.Next,water infiltration rate decreased as irrigation time increased,and coarse soils had the lowest average infiltration rate under greater negative pressure.Finally,salt content increased with distance from the irrigation emitter and with increased negative pressure.Further,coarse soils were found to have decreased desalination under greater negative pressure.Thus,soil texture has a strong effect on NPI efficiency.However,by adjusting pressure values in accordance with soil texture,soil water content can be controlled and maintained.These findings are important to the improvement of NPI systems,increasing their practicality for agricultural use.
基金supported by the National Natural Science Foundation of China (30471228)the National Key Technology R & D Program of China (2006BAD16B01)
文摘A field experiment study was conducted in Bashang Plateau in North China in 2008 to determine the effect of three first cutting dates on the growth and water use efficiency(WUE) of Siberian wildrye(Elymus sibiricus L.) in the agropastoral ecotone of North China(APENC).The experiment was conducted in a split plot design with three replications with water supply regime as the main plot treatment and first cutting date as the subplot treatment.Two water supply regimes were used,which included rain-fed treatment as control(CK) and a single irrigation and straw mulch treatment(W).Three first cutting date treatments were conducted at early heading stage on July 1(E),at late heading stage on July 12(L),and at flowering stage on July 27(F),respectively.The results showed that the forage yield and WUE were the lowest at early heading stage harvest,while the highest at flowering stage either in CK or W treatment.Under combined CK and W treatments,average forage yields of the F subplots were 2 900 and 6 703 kg ha-1,and the values of WUE were 0.82 and 2.28 kg m-3,respectively.Under the CK treatment,forage yields of the E and L subplots were 43.8 and 41.9% lower than the F subplots,and their values of WUE were 46.2 and 50.3% lower than F,respectively.Under the W treatment,the forage yields of the E and L subplots were 74.9 and 61.6% lower,and their values of WUE were 78.1 and 63.3% lower,respectively,as compared with F subplots.Therefore,earlier first cutting did not increase the regrowth of Siberian wildrye and improve the mismatch between rainy season and the period of high growth potential of the grass in the semiarid APENC.
文摘Some soil properties were studied in relation soil aggregate along a climatologically region and different crop land use in the Northeast of Sulaimani City/Kurdistan Region of Iraq. Five locations were selected along these regions ranging from semiarid to sub-humid climatologically conditions. The soil physical, chemical properties, aggregate stability and size distribution were analyzed. A mean-weight-diameter (MWD) value was determined on 5 soils, which was the sum of the percentage of soil on each sieve (6, 3, 1.5, 0.75, 0.375 and 0.125 mm). The results of the measurements could evaluated with linear correlation coefficients for the relationships between aggregate stability (MWD) and soil physical and chemical properties of the different crop land use. The correlation coefficient for the relationship between aggregate stability and organic matter was highly significant (P < 0.0l%) which is in agreement with the findings of [1]. Generally large aggregates (large 6, 3, 3 - 1.5 mm) were present in highest proportions in the most semiarid of the studied areas. Aggregates 0.75 - 0.125 mm were positively correlated to fine, very fine sand and silt fractions and to organic matter. Stability of aggregates showed a positive correlation with clay content and organic matter content, while the carbonate content was strongly correlated with aggregate stability. The land use history affecting soil overlaps the pattern of climatological situations and cultivated crop lands and has to be taken into account. Aggregate size distribution and stability can be used as indicator of soil conservation and productivity.
基金Project supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX2-413-3)National Natural Science Foundation of China (No.30390080)National Basic Research Program of China (No.2005CB121108)
文摘响应到稻田的脲申请的氨挥发损失，氮利用效率，和米饭收益在 Wangzhuang 镇上被调查， Changshu 城市，江苏省，中国。N 化肥处理，适用在三倍，是 0 (控制) ， 100， 200， 300，或 350 kg N 哈 ? 1。在脲被用于地面水以后，一个连续气流包围方法被用来在稻田测量氨挥发。通过氨挥发的全部的 N 损失通常与 N 申请率，和申请评估的二更高的 N 增加了(300 和 350 kg N 哈 ? 1 ) 证明 N 的更高的比率通过氨挥发输了到应用 N。由在全部米饭期间，生长上演的氨挥发的全部的氨损失从 9.0% ～ 16.7% 应用 N 。增加申请率通常减少了在到在植物的 N 的种子的 N 的比率。为所有 N 处理，氮肥利用效率从 30.9% ～ 45.9%。有最高的 N 率的剩余 N 导致了米饭植物，氮肥利用的减少的率，和减少的米饭收益的住宿。从这个实验计算，最节俭的 N 化肥申请率是 227 kg 哈 ? 1 为在泰胡·莱克区域的水稻土的类型。然而，推荐适当 N 化肥申请率以便植物生长被提高，氨损失被减少能改进大米的 N 利用效率。
基金financially supported by the National Natural Science Foundation of China (41071206)
文摘Innovative measure is a urgent requirement for managing the huge volume of municipal sewage sludge. The hydrothermal carbonation(HTC) shows some potential advantages for using hydrochar as a soil conditioner. The aim of this work was to investigate the properties of hydrochars, by means of the HTC of municipal sewage sludge under different temperatures(190 and 260°C) and reaction hours(1, 6, 12, 18 and 24 h). The HTC led to the decreases of N, O and H contents by more than 54.6, 37.9 and 10.0%, respectively, and slight changes of C content. The Py-GC-MS analysis showed that a large proportion of fatty acids, in particular hexadecanoic acid, transferred into alkenes, olefins and aromatic compounds. The 13C-NMR and fourier transform infrared spectra(FTIR) confirmed the transformation and changes in chemical structure in which hydrochar contained lower oxygen-containing organic C of O-alkyl, carboxylic and carbonyl C and aliphaticity, but higher aromatic C and aromaticity. The rich hydrophobic functions induced in high positive charges in the charred sludge. The HTC facilitated the pore structure development, proved by higher specific surface area and specific pore volume, with a maximum of 17.30 and 0.83 cm3 g-1, respectively. The availabilities of N, P and K markedly reduced during HTC treatment. The activities of most heavy metals were depressed though they accumulated in the hydrochar. Further work is required to investigate the values and risk of the charred sludge amended to soil.
文摘Tillage greatly influences the aggregation and stability of soil aggregates. This study investigated the effects of conservation tillage on soil aggregate characteristics. During a four-year study period (2001-2005), soils were sampled from no-tillage (NT), rotary tillage (RT), and conventional tillage (moldboard tillage, CT) plots at the Luancheng Agriculture and Ecology Experimental Station in Hebei Province, China, and the amount, size distribution, and fractal dimension of the aggregates were examined by dry and wet sieving methods. The results indicated that NT significantly increased the topsoil (0-5 cm) bulk density (BD), while RT maintained a lower BD as CT. Dry sieving results showed that NT had higher macro-aggregate content (R0.25), and a larger mean weight diameter (MWD) and geometric mean diameter (GMD) than other treatments in the 0-10 cm layer, while RT showed no difference from CT. In wet sieving, results showed that most of the aggregates were unstable, and the MWD and GMD of water-table aggregates showed the trend of NT > RT > CT. At 0-5 cm layer, the fractal dimension (D) of water-stable aggregates under NT was lower than it was under RT and CT. At 5-10 cm, RT yielded the highest D, and showed stability. After four years, NT increased the aggregation and the stability of soil aggregates; while due to intense disturbance, the aggregation and stability of the upper layer (0-10 cm) under RT and CT decreased.
基金funded by the National Science and Technology Supporting Programs of China under Grants No. 2006BAD15B01 and 2006BAD02A14
文摘The structure of the "black soil" in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage (CT) practices. In this study, micromorphological observation and image analysis of soil thin sections were conducted to evaluate the impacts of 21 years (1986-2007) of no tillage (NT) on soil structure as compared to CT in an experiment near Gongzhuling City, Jilin Province. Soil organic matter (SOM), wet aggregate stability and saturated hydraulic conductivity (Ks) were also analyzed. Total SOM was not significantly affected by tillage systems, but fresher SOM was observed in the surface layer under NT. The aggregates under NT showed different hierarchies in the form of crumbs, and the mean weight diameter (MWD) of NT was significant higher than that of CT in the surface layer. Platy and blocky aggregates were frequently observed in the lower layers under CT practice. The compound pore structure with intertwined intra-and interaggregates pores under NT was well developed in a layer from 0-5 cm to 20-25 cm. While under CT system, more inter-aggregate pores and fewer intraaggregate pores were observed, and planes and channels were frequently found in the 20-25 cm layer, where macroporosity decreased significantly and a plow pan was evident. The Ks values of NT were significantly lower at 0-5 cm but significantly higher at 20-25 cm compared with CT, which showed the same trend with macroporosity. These results confirmed that long-term CT practice fragmented the tillage layer soil and compacted the lower layer soil and formed a plow pan. While long-term NT practice in the black soil region favored soil aggregation and a stable porous soil structure was formed, which are important to the water infiltration and prevent soil erosion.
文摘Since industrial revolution,the atmospheric CO2concentration has kept a continuous increase by more than 2.2 ppm yr-1,and approaches to almost 400 ppm at present(Jouzel 2012).China has become the largest country of greenhouse gas emission(GHG),and confronts with great challenge to mitigate GHG.Soil is widely considered not only as an important carbon sink in terrestrial ecosystem,but greenhouse gas resource as well.It is estimated that the soils
文摘Land use changes from natural ecosystems into managed ecosystems resulted in negative impact on soil structure and quality. The purpose of this study was to determine the influences of different land-use types on physical and chemical properties of soils in Sulaimani governorate. Land use systems including natural forest, pastureland and agriculture were identified. Ten of soil samples were collected from the 0 - 30 cm depth, and some soil physical and chemical properties of soil were determined. The land use alters from forest to agriculture resulting in significant decrease in organic matter, calcium carbonate and soil surface area and with this change, dispersion ratio affected on the physical property. The value of DR was highest in the Zrguezi Gawra cultivated with Cucumber and the lowest value in Dukan is 13%, and correlation coefficient between dispersion DR with sand, silt and bulk density is positive, value is (0.4979, 0.0126 and 0.7536) respectively, and with clay and specific surface area (SSA) the correlation coefficient value is (-0.7281 and -0.4466).
文摘Rubber is an economically important perennial crop in Myanmar for latex production. As the rubber plantation area increases yearly, the requirement of vigorous rubber seedlings for its establishment plays a central role. The success of rubber plantations depends on some farming practices such as using different compost or other materials in the potting soil-medium, varietal selection for stock and scion in the budding process, and fertilizer application methods. The objective of this study was to assess the farmer’s practices in the establishment of rubber nurseries in mostly rubber planted areas in Myanmar. The survey interviewed 60 respondents from three townships in Mon State, namely Mudon, Kyaikmaraw, and Thanbyuzayat. The response data were analyzed through the descriptive method. This survey exposed the potentially active operators (middle age of 30 - 60 years) in rubber nursery production. Local experienced farmers usually raised the budded seedlings with 15 cm × 23 cm polyethylene bag in all study regions. Most farmers selected multi-clonal seed for stock and BPM 24 for scion according to the local market demand and high latex yield. All survey areas used both organic and inorganic fertilizers for nutrient management. Compost is a chief component of growing medium in their nursery production. However, making compost and high demand of the compost were local constraints. Therefore, this survey suggested improving the proper composting method for rubber nursery establishment.
文摘Protecting and preserving our environmental systems require the ability to understand the spatio-temporal distri- bution of soils, parent material, topography, and land cover as well as the effects of human activities on ecosystems. Space-time modelling of ecosystems in an environmental digital library is essential for visualizing past, present, and future impacts of changes occurring within such landscapes (e.g., shift in land use practices). In this paper, we describe three novel features, spa- tio-temporal indexing, visualization, and geostatistical genre, for the environmental digital library, Environmental Visualization and Geographic Enterprise System (ENVISAGE), currently in progress at the University of Florida.
基金The authors are grateful for financial support provided by the IAEA(CRP14483)China National Science and Technology Pillar Program(2012BAD05B02).
文摘The North China Plain(NCP)is a major grain production area in China,but the current winter wheatsummer maize system has resulted in a large water deficit.This water-shortage necessitates the improvement of crop water productivity in the NCP.A crop water model,AquaCrop,was adopted to investigate yield and water productivity(WP)for rain-fed summer maize on the piedmont of the NCP.The data sets to calibrate and validate the model were obtained from a 3-year(2011–2013)field experiment conducted on the Yanshan piedmont of the NCP.The range of root mean square error(RMSE)between the simulated and measured biomass was 0.67–1.25 t·hm^(–2),and that of relative error(RE)was 9.4%–15.4%,the coefficient of determination(R^(2))ranged from 0.992 to 0.994.The RMSE between the simulated and measured soil water storage at depth of 0–100 cm ranged from 4.09 to 4.39 mm;and RE and R^(2) in the range of 1.07%–1.20%and 0.880–0.997,respectively.The WP as measured by crop yield per unit evapotranspiration was 2.50–2.66 kg·m^(–3).The simulated impact of long-term climate(i.e.,1980–2010)and groundwater depth on crop yield and WP revealed that the higher yield and WP could be obtained in dry years in areas with capillary recharge from groundwater,and much lower values elsewhere.The simulation also suggested that supplementary irrigation in areas without capillary groundwater would not result in groundwater over-tapping since the precipitation can meet the water required by both maize and ecosystem,thus a beneficial outcome for both food and ecosystem security can be assured.
基金supported by the National Natural Science Foundation of China (51009151,51109225 and 91125017)the National Basic Research Program of China (2006CB403405)the Special Scientific Fund sponsored by IWHR for Department of Irrigation and Drainage (1209)
文摘Transpiration and photosynthesis are two closely related and intercoupled processes that dominate the physiological activities and yield of crops. Therefore, there is a need to study water-carbon coupling modeling at various scales to increase water use efficiency (WUE). Using a summer maize field in North China as an example, the variations in leaf and canopy photosynthesis and transpiration (or evapotranspiration) were analyzed. The synthetic model of photosynthesis-transpiration based on stomatal behavior (SMPT-SB) was then calibrated and validated at the two scales. The leaf photosynthesis and transpiration, as well as the canopy photosynthesis and evapotranspiration, have a consistent diurnal trend. However, the canopy evapotranspiration is affected more by topsoil moisture content. The regression coefficient between leaf photosynthesis, transpiration, and WUE estimated by the SMPT-SB and the measured values was found to approach 1, with a coefficient of determination of more than 0.74. The relative error between the two sets of values is less than 11%. Therefore, the SMPT-SB could express fairly well leaf photosynthesis, transpiration, and WUE. The estimated canopy-scale photosynthesis by the SMPT-SB is also in good agreement with the measured values. However, this model underestimates the canopy evapotranspiration when the topsoil has high moisture content and therefore overestimates, to a certain extent, the canopy WUE.
基金supported by the National Natural Science Foundation of China(61705195).
文摘Deep learning and computer vision have become emerging tools for diseased plant phenotyping.Most previous studies focused on image-level disease classification.In this paper,pixel-level phenotypic feature(the distribution of spot)was analyzed by deep learning.Primarily,a diseased leaf dataset was collected and the corresponding pixel-level annotation was contributed.A dataset of apple leaves samples was used for training and optimization.Another set of grape and strawberry leaf samples was used as an extra testing dataset.Then,supervised convolutional neural networks were adopted for semantic segmentation.Moreover,the possibility of weakly supervised models for disease spot segmentation was also explored.Grad-CAM combined with ResNet-50(ResNet-CAM),and that combined with a few-shot pretrained U-Net classifier for weakly supervised leaf spot segmentation(WSLSS),was designed.They were trained using image-level annotations(healthy versus diseased)to reduce the cost of annotation work.Results showed that the supervised DeepLab achieved the best performance(IoU=0.829)on the apple leaf dataset.The weakly supervised WSLSS achieved an IoU of 0.434.When processing the extra testing dataset,WSLSS realized the best IoU of 0.511,which was even higher than fully supervised DeepLab(IoU=0.458).Although there was a certain gap in IoU between the supervised models and weakly supervised ones,WSLSS showed stronger generalization ability than supervised models when processing the disease types not involved in the training procedure.Furthermore,the contributed dataset in this paper could help researchers get a quick start on designing their new segmentation methods in future studies.
文摘The effect of a machine feeding rate(FR;1,1.5 and 2 Mg/h)and/or three levels of selected fineness degree(FD;3,5 and 7 mm)on machine performance,pellet physical parameters,required energy and production cost of three main types of broilers diets were examined in this experiment.The examined broiler diets were formulated to meet the Ross 308 strain requirements.A complete factorial design(3×3×3)was used to identify the effects of studied factors on the pellet mill machine and pellet production.The obtained results indicated that the pellet mill productivity significantly(p˂0.001)improved through increased pellet mill feeding rate level.In addition,the machine pelleting efficiency was found to be significantly affected by all studied variables and their interactions.While the total power consumption of the machine showed no variations under the impact of the tested factors or with any of their combinations.Regarding the pellet physical quality indices,all broiler diets with all selected FD and lower FR had the maximum durability and bulk density levels.Furthermore,lower feeding rates were associated with higher hardness degrees.The lowest production costs were substantially correlated with high FR and intermediate FD(5 mm).Furthermore,production costs were determined to be reduced in finisher broiler diets under different feeding rates.Moreover,manufacturing costs of finisher broiler meals were observed to decrease in several feeding rates.Overall,these findings indicate the capabilities of producing high-quality pellets and reducing the needed production costs by optimizing feeding rates to 2 Mg/h and 2 mm fineness in broiler diets.
基金supported by the National Program on Key Research Project(2016YFC0501703)Basic Research program of Natural Science in Shaanxi(2017jz008)+1 种基金Esmat F.Ali is also thankful to Taif University Researchers Supporting Project number(TURSP-2020/65)Taif University,Saudi Arabia,for the financial support and research facilities.
文摘Land use changes profoundly affect the equilibrium of soil organic carbon(soC)sequestration and greenhouse gas emissions.With the current global climatic changes,it is vital to understand the influence of ecological restoration and conservation management on the dynamics of soC under different land uses,especially in erosion-endangered Loess soils.Therefore,we investigated changes in soc through a suit of labile fractions,namely:light fraction organic C(LFOC),heavy fraction organic C(HFOC),coarse particulate organic C(CPOC),fine particulate organic C(FPOC),and dissolved organic C(DOC),from two forests i.e.,Robinia pseudoacacia(RP)and Platycladus orientalis(PO),with different ages,in comparison with farmland(FL).The SOC and STN contents significantly increased over 42 years in the RP forest where the contents of CPOC and FPOC were significantly higher than in the FL.Moreover,total SOC and its labile fractions,in the studied land use types,significantly correlated with soil CacO3,pH,and STN contents,indicating their key roles in SoC sequestration.The results reported here from different vegetation with different ages provide a better understanding of sOC and STN alterations at different stages of vegetation restoration.Our findings suggest that long-term natural vegetation restoration could be an effective approach for SoC sequestration and soil conservation on the Loess soil.
基金Financial support for this work was provided by the United States Department of Agriculture,Natural Resources Conservation Service(Grant no.G17AC00337)。
文摘Biochar is known to ameliorate soil fertility and increase crop yield;however,information regarding its effects on soil chemical and biological properties remains limited.The experiment was conducted to study the short-term impacts of dif-ferent types of biochar on soil C fractions,enzyme activities,and microbial community structure at depositional and eroded landscape positions at different sampling times[before planting,after planting,and after harvesting of soybean(Glycine max L.)].Three biochar materials,produced from C-optimized gasification of corn(maize,Zea mays L.)stover(CS),pon-derosa pine(Pinus ponderosa Lawson and C.Lawson)wood residue(PW),and switchgrass(Panicum virgatum L.)(SG),and dairy manure(DM)and mixture of dairy manure and pinewood biochar(DMP),were applied at a rate of 10 Mg ha^(−1) to depositional and eroded landscape positions.Data showed that the application of DMP and sole application of DM treat-ments significantly increased the labile C fractions at the depositional and eroded landscapes.The addition of DM and DMP increased the activities ofβ-glucosidase and urease enzymes,and those are involved in C and nitrogen cycling at depositional and eroded landscape positions.There were no significant differences between different biochar materials.However,there was an increase in soil microbial community structure in the DM and DMP treatments at both the landscape positions.In conclusion,our study revealed that DMP and sole application of DM influenced the soil labile C pool,enzyme activities,and microbial community structure at both the landscape positions for different sampling times.
基金supported by the Pedometrics, Landscape Analysis, and GIS Laboratory, Soil and Water Sciences Department, University of Florida, USA
文摘The applicability, transferability, and scalability of visible/near-infrared(VNIR)-derived soil total carbon(TC) models are still poorly understood. The objectives of this study were to: i) compare models of three multivariate statistical methods, partial least squares regression(PLSR), support vector machine(SVM), and random forest methods, to predict soil logarithm-transformed TC(logTC) using five fields(local scale) and a pooled(regional-scale) VNIR spectral dataset(a total of 560 TC spectral datasets), ii)assess the model transferability among fields, and iii) evaluate their up-and downscaling behaviors in Florida, USA. The transferability and up-and downscaling of the models were limited by the following factors: i) the spectral data domain, ii) soil attribute domain,iii) methods that describe the internal model structure of VNIR-TC relationships, and iv) environmental domain space of attributes that control soil carbon dynamics. All soil logTC models showed excellent performance based on all three methods with R^2> 0.86,bias < 0.01%, root mean squared error(RMSE) = 0.09%, residual predication deviation(RPD) > 2.70%, and ratio of prediction error to interquartile range(RPIQ) > 4.54. The PLSR method performed substantially better than the SVM method to scale and transfer the TC models. This could be attributed to the tendency of SVM to overfit models, while the asset of the PLSR method was its robustness when the models were validated with independent datasets, transferred, and/or scaled. The upscaled soil TC models performed somewhat better in terms of model fit(R2), RPD, and RPIQ, whereas the downscaled models showed less bias and smaller RMSE based on PLSR. We found no universal trend indicating which of the four limiting factors mentioned above had the most impact that constrained the transferability and scalability of the models. Given that several factors can impinge on the empirically derived soil spectral prediction models, as demonstrated by this study, more focus on their applicability and scalability is needed.
