Study of drought stress and manure effects on soybean growth Indices

Increasing of soil fertility is one of the agronomic management methods to overcome environmental stresses which are attained by preparing nutrition with chemical and organic fertilizer usage. An experiment lay out in split plot basis of randomized complete block design with four replications in order to evaluation of reaction of line L17 soybean to cattle manure usage. Stress factor was in main plot consisting three different irrigation levels after 50، 100، and 150 mm evaporation from pan class A (including control، mid and sever stress) and cattle manure factor was in subplot including application of 0، 15، 30 and 40 t ha-1. the results showed that the maximum leaf area index (LAI) decreased by increasing of drought stress and this reduction was from 5. 1 in favorable irrigation to 3. 4 in sever drought stress. This reducing rate for accumulated dry matter of shot was from 893. 64 to 558. 02 g m-2 and for crop growth rate (CGR) was 1. 59 to 0. 94 g m-1 GDD-1. By increasing the amount of manure، the maximum leaf area index (LAI) increased from 3. 7 in lake of cattle manure usage to 5. 4 in use of 45 t ha-1 manure. This increasing rate for dry matter accumulation was from 601. 07 to 832. 26 g m-1 growth degree day -1 and for CGR was from 0. 99 to 1. 43 g m-2 GDD-1.