Effects of Long-term Application of Chemical Fertilizer and Rice Straw on Potassium Transport in Double Cropping Rice Field

The effect of rice yield,uptake potassium amount of crop,potassium concentration dynamic changes of surface water and different soil depth water and potassium balance on double cropping rice under intensive cropping period of 3 years(2010-2012)was studied using the data obtained from the long-term fertilization experiment(1981-2012)under double cropping rice system.The results showed that application potassium fertilizer could increase the rice grain and straw yield.Potassium uptake from the soil significantly increased with increasing potassium fertilizer application.The average annual amount of potassium absorption was in the order of NPK+RSNPK NP+RSCK NP.Potassium concentration differences of surface water in those treatments manifested the following 40 days after fertilizer application.Potassium concentration in the surface water from early rice and late rice decreased gradually with extending time.The 40 days after application potassium fertilizer,potassium concentration of surface water had little difference among those treatments,changed from 2.34mg/L to 3.43mg/L in early rice,and changed from 2.03mg/L to 2.97mg/L in late rice.Potassium concentration of leaching water gradually decreased with prolonging fertilization time in different soil depth from three applied potassium fertilizer treatments,and had less change in NP and CK treatments without potassium fertilizer application.During 70days period after potassium fertilizer application,potassium concentration of leaching water in three treatments with K fertilizer application decreased with the increase of soil depth.The order of potassium concentration of leaching water was NPK+RSNPK NP+ RSCK NP in three different soil layers from early rice and late rice.Except NPK+RS treatment,the other four treatments were in potassium deficiency.These results demonstrated that the long-term application of potassium fertilizers and rice straw returning in reddish soil in double cropping rice field had significant effects on increasing yield,promoting potassium nutrient cycling,maintaining soil potassium balance and improving soil potassium fertility.