Effects of long-term potassium application and wheat straw return to cinnamon soil on wheat yields and soil potassium balance in Shanxi

Under the condition of wheat-fallow rotation on a calcareous cinnamon soil in Shanxi province, a long-term field experiment was conducted for 16 years to study the effects of long-term potassium(K)application and wheat straw return on wheat yields and soil K status. The results show that application of nitrogen(N)and phosphate(P)fertilizer only without K addition to the system(NP treatment)results in an average yield of 5.5 t/ha and an average annual deficit of 104.3 kg/ha, which indicates there is a serious deficit of soil potassium. Compared with their initial values, contents of soil available K and slowly available K are decreased by 23.6% and 14.3%, respectively. Compared with the NP treatment, the average wheat yield is increased by 10.2% under the application of K fertilizer(NPK treatment)at the rate of K2O 150 kg/ha annually, and is increased by 6.6% under the straw return treatment(NP+St treatment). The combination of wheat straw return to soil and K application(NPK+St treatment)can increase wheat yield by 17.6%, and K uptake by wheat plants is increased by 32.0 kg/ha. Compared with their initial values, contents of soil available K and slowly available K are increased by 38.6% and 11.0%, respectively. On the base of N and P fertilizer application, wheat grain yield, biomass yield and K uptake by wheat plants are significantly increased under the long-term K application or wheat straw return, and the stability of yield and plant K uptake are improved and the yield variation among the 16 crop seasons is reduced as well.