Replacement ratio of nitrogen and potassium fertilizer by straw incorporation in early rice under the same nitrogen, phosphorus and potassium input

ObjectivesEffects of total straw incorporation with chemical fertilizers in situ on the N, P and K use efficiencies of early rice of double cropping were studied under the same N, P and K input in the long run to provide base support for effective utilization of the southern straw resource and sustainable soil fertility, and rational application fertilizers.

MethodsA long-term field experiment located in the cultivated land quality monitoring system on straw incorporation and soil fertility (Wenzhen Town, Jiangxi Province) was carried out, and early rice cultivar, Luliangyou 996, was selected as tested material. Plant samples were collected from six treatments: total straw incorporation (TS), straw burning and straw no-incorporation, containing application chemical fertilizer and no chemical fertilizer, respectively, all the treatments, except blank control, were input the same amount of N, P and k nutrients. The N, P and K accumulation, translocation and use efficiencies were analyzed at the transplanting, tillering, panicle initiation, heading and maturity stages of early rice in 2015.

ResultsWith supplement of chemical fertilizer, the total straw incorporation treatment could stably increase grain yields of early rice within six years, and the yields were 2.9% and 6.4% higher than those in treatments of the straw burning and pure chemical fertilizer treatments, and compared with no chemical fertilizer and no straw treatment, the increments were from 23.8% to 26.0%. Compared with the straw burning and straw no-incorporation, no matter the fertilization treatments and blank, the straw incorporation had the higher K content and N, P and K accumulation at the growth stages, but the N and P contents were higher at the later growth stages. The N, P and K accumulation amounts in the fertilization treatments were higher than those in the no fertilization treatments. The straw incorporation enhanced the N, P and K fertilizer agronomy efficiencies (AE), recovery efficiencies (RE) and partial factor productivity (PFP), and increased the K harvest index significantly, while the N and K use efficiencies were significantly different among the treatments. Meanwhile, the straw incorporation increased the N, P and K transfer amounts, transfer rates and contribution to grain nutrient of the stems and sheaths, but no differences were observed in the leaves among treatments.

Conclusions The straw incorporation with application fertilizers could increase the grain yield, and improve the accumulation and translocation of applied N, P and K, and their use efficiencies in the long-run. Replacing of N 29.5%, P₂O₅ 4.0% and K₂O 50.0% with straw for fertilizer N, P and K in the straw incorporation is proved to be a feasible way to realize soil nutrient management in the southern rice zone contrast to the straw burning.