摘要
土地利用方式以及不同农作物对土壤流失有明显的影响 ,定量评价不同作物在土壤流失中的作用 (作物覆盖因子 )是土地利用和水土保持规划的重要依据。研究的目的在于计算黄土高原主要农作物不同生长阶段的土壤流失强度与裸露地的比率 ,为计算土壤侵蚀作物覆盖因子应用。通过对甘肃天水和陕西安塞水土保持试验资料的分析 ,计算了 7种主要作物 6个农作期的土壤流失比率表 ,并对黄土高原 7种作物覆盖因子进行了计算 ,其值在 0 .2 3～ 0 .74之间 ,按此方法计算的作物覆盖因子值与观测多年平均土壤流失比率基本一致。但该方法的优势在于可以根据土壤流失比率表和不同的降雨侵蚀力分布曲线计算不同地区的 C值 。
Land use and crop characteristics influence soil loss obviously,so that a quantitative evaluation of the effect of different crops on soil loss(crop factor)is essential to land use and soil conservation planning.The effect of a given crop on soil erosion varies a great deal within the period from seeding to harvest because crop characteristics and canopy cover varies greatly in different seasons.Moreover,the distribution of the erosive rainfall within a year differs for different localities.Therefore,crop factor that takes both the protection of crop and rainfall erosion index into account is widely adapted in soil loss prediction in many countries.Although some research on C (crop)factor have been reported in China,there were much disagreement between those C values;so no C values or related parameters is widely adapted in China so far.The main reason is that the present C values seldom include the influence of rainfall patterns and variety of crop coverage in a year;or crop stages were not defined clearly.Another reason is the compared fallow conditions are not consistent.The purpose of this study is to calculate soil loss ratio from different types of cropland to bare fallow land,on the basis of which crop factor on loess plateau is estimated. 108 plot year observation data from Tianshui,Gansu during 1945～1953(slope length 20m,slope width 5m,slope gradient 5°,8°,14°,17°,including lentil,winter wheat,buckwheat,maize intercropping with soybean grown by traditional tillage in rotation)and 48 plot year observation data from Ansai,Shaanxi during 1987～1992(slope length 20m,slope width 5m,slope gradient 25°,including buckwheat,potato,millet,soybean,which are grown by traditional tillage in rotation,fallow and two types of grass,sainfoin adsurgens)on loess plateau was analyzed in this study. In order to take account of variance of crop coverage,a crop year is divided into the following six crop stage periods according to crop coverage change with time:fallow(from plowing to preparing seedbed),seedbed(preparing seedbed to 10% coverage),established(10%～50% coverage),development(50%～75% coverage),mature(75%～harvest)and residue and stubble(harvest plowing).The length of each crop stage of specific crop is given in a table. Obtaining soil loss ratios(SLR)for individual crop stage periods are essential to derive the value of C factor.By analysis of 156 plot soil loss observations from two experimental field stations,soil loss ratios for each crop stage period of 7 crops are presented.In Ansai,soil consolidation caused the esodibility of fallow plots to decrease significantly after the only tillage in spring and regression analysis shows that monthly average erodibility(Soil Loss/ PI 30)decreases linearly within six months after tillage with the R 2=0.858.In order to keep the compared fallow conditions principally consistent,each soil loss was adjusted to the average level of the fallow plots by multiplying a modifying factor.Factor in the first month after tillage is 0 68;the second month,0.79;the third month,0.94;the fourth month,1.16;the fifth month,1.51;the six month,2.17.Then SLR of every stage of 4 crops was calculated.In Tianshui station,measured soil losses from cropped plots were compared with seedbed within 20 days after planting or plots two months after harvest(quasi fallow)because of no experimental plot kept fallow.When SLR was calculated,all chosen observation data from 27 rainfall events in each of which “quasi fallow plots” can be identified was grouped according to crop stage of different crops.For each rainfall event,12 plot observations were divided again into 4 sub groups according to slope.There is a “quasi fallow plots” among each sub group.The ratio of total soil loss from each crop stage to the total soil loss from corresponding “quasi fallow plots” with same slope is calculated as the SLR of that crop stage. On the bases of soil loss ratios presented here and erosion index distribution data,annual average crop factors for the seven crops including lentil,
出处
《生态学报》
CAS
CSCD
北大核心
2001年第7期1050-1056,共7页
Acta Ecologica Sinica
基金
国家科技部"973"项目 ( G2 0 0 0 0 1 860 2 )
国家杰出青年基金 ( 4972 51 0 3)资助项目
