A randomized complete block design ( rcbd ) has been used under the field conditions to compare the effect of four treatments : 1 ) entire quantity of straw returned to the soil , but not cut into pieces ( treatment a ) , 2 ) half quantity of straw returned , not cut into pieces as in treatment a ( treatment b ) , 3 ) half quantity of straw cut into pieces returned ( treatment c ) , 4 ) ck ( treatment d ) , without any straw returned to the filed 田間實驗采用隨機區組法,分四種情況: 1 )全量整株稻草還田; 2 )半量整株還田; 3 )半量切碎還田4 )對照,即除根茬外無額外稻草還田四個處理。試驗結果表明,除處理2外,所有處理對土壤有機質的影響不明顯,但稻草還田處理降低了土壤的容重,這意味著土壤的孔隙度增加了。