The effect of straw mulch on nitrogen, phosphorus and potassium uptake and use in hybrid rice

To optimize straw application and understand the effects of straw mulch and straw nutrient release on rice nutrient uptake, we investigated the effects of two types of straw mulch (S1—wheat straw and S2—rapeseed straw) and no straw mulch (S0) on straw decomposition and nutrient release; rice growth and nutrient accumulation; and the nitrogen, phosphorus and potassium stimulation ratio and recovery efficiency of straw on rice in 2013 and 2014. Results showed that wheat straw mulch was associated with a higher decomposition ratio and total nutrient release and frequent rainfall could further increase decomposition and nutrient release in the 0–30 days after transplanting growth stage. Remarkably, the later stages were associated with decreased decomposition and nutrient release, especially on rapeseed straw mulch. Wheat and rapeseed straw mulch had obvious effects on rice growth and nutrient uptake. Compared with S0, S1 could distinctly promote dry matter accumulation and increase the levels of nitrogen, phosphorus and potassium in the rice plant at each growth stage, as well as increase grain yield in 2013 and 2014. By contrast, S2 inhibited rice growth; decreased nitrogen, phosphorus and potassium uptake and dry matter accumulation in rice plants during the early growth stage, while significantly improving that in the following growth stage; but decreased grain yield under rainy and cold weather conditions (2014). Compared with S0, wheat and rapeseed straw mulch increased total nitrogen, phosphorus and potassium accumulation in rice plants by 1.81–10.79%, 2.70–42.21% and 16.41–17.92%, respectively, thus improving nitrogen, phosphorus and potassium utilization.