Effect of different straw return modes on potassium balance
and potassium pool in cinnamon soil

【Objectives】A long-term location experiment was conducted in the main growing area of spring maize in Shanxi Province, northern China, to study the effective modes of straw returns with high yield and potassium balance.【Methods】 The long-term experiment was conducted from 1992 to 2011 in typical cinnamon soil with spring maize as tested crop. Four treatments were included, no straw return (CK),direct straw mulching (SM), pulverized straw mulching (SC) and straw return after livestock digestion (cattle manure, CM). Straw was returned 6 t/hm2, and the wet cattle manure amount were 45 t/hm2. The 0-20 cm soil sampleswere collected every year after harvest and the potassium contents of different fractions were analyzed. In 2011, the soil K contents in 0-20, 20-40, 40-60, 60-80 and 80-100 cm soil samples were collected and the K contents were analyzed.【Results】 1) Compared with no straw return, all the three straw treatments significantly increased the crop yield by 11.58%-20.91%, and the yield increments follow the sequence of CMSMSCCK. 2) The contents of available potassium, slowly available potassium and total potassium in straw return treatments were higher than control, and the proportion of mineral potassium in these treatments became lowered and other fractions raised. 3) Compared with the beginning of the experiment, soil available potassium content was significantly raised in long-term straw return treatments (SM, SC and CM), whereas that gradually decreased in control. 4) Straw return stimulate the apparent potassium absorption, leading to a gradual depletion of soil potassium, with apparent potassium equilibrium coefficients in the straw return treatments were 0.45,0.56 and 0.74,respectively; but for all of that, the straw return practice still helped sustain soil potassium balance and alleviate the depletion of soil potassium pool, and maintain a stable soil potassium supply, compared with control. 【Conclusions】 Straw return to land after livestock digestion (cattle manure, CM) can sustain soil potassium balance, restore soil potassium after consumption by crops, alleviate the depletion of soil potassium pool, and maintain a stable soil potassium supply.