Long-term straw returning improve soil K balance and potassium supplying ability under rice and wheat cultivation

Zhiyi Zhang,Dongbi Liu,Ying Xia,Maoqian Wu,Xianpeng Fan,Fulin Zhang

doi:10.1038/s41598-021-01594-8

Zhiyi Zhang, Dongbi Liu + Show 4 more

Open Access

https://doi.org/10.1038/s41598-021-01594-8

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Abstract

The aims of the present study were to provide scientific bases for rational use of crop straw to substitute chemical potassium (K) input. The effects of potassium fertilization and straw incorporation on soil K balance and K supplying in a long-term (14 years) field experiment. Five treatments were examined: (1) no fertilization (CK); (2) mineral fertilizing (NPK); (3) straw 6000 kg h m−2 (S); (4) NPK with straw 3000 kg h m−2 (NPK1/2S); and (5) NPK with straw 6000 kg h m−2 (NPKS). K composition, K balance and quantity-intensity (Q/I) relationship were studied. Under no fertilization or low straw returned conditions, soil K was unbalanced and deficienct seriously. Straw return at 6000 kg h m−2 per season with fertilization improved the soil potassium supply and K balance. Long-term K surplus (4 or 5 years), compared with NPK, the NPKS significantly increased non-special K adsorption (Knsa) and non-exchangeable K (Kne) by 5.7–11.2 mg kg−1 and 65.7–128.1 mg kg−1, respectively. Q/I relationship showed cropping without straw K or without fertilizer K resulted in lower quantity (nonspecifically and specifically held K i.e. – ∆K0 and Kx) and intensity (equilibrium activity ratio i.e. CR0K) of K in tested soils. K-fertilization with straw maintain higher exchangeable K (EK0) and a higher difference between EK0 and minimum exchangeable K(EKmin), and would help to prevent depletion in non-exchangeable pool of soil K under intensive cropping. Additionally, The straw return mainly decreased potential buffering capacity for exchangeable pool (PBCKn), 43.92–48.22% of added K in soil might be converted to exchangeable pool while it was 25.67–29.19% be converted to non-exchangeable pool. The contribution of exchangeable K towards plant K uptake would be higher in the soil with straw than the soil without straw and the non-exchangeable K would be the long-term fixed K as a supplement to the potassium pool. K fertilizer with 6000 kg h m−2 straw return in each crop season increased soil available K and slowly available K. The findings underlined importance of the straw return and contribution for sustain K supplying ability of soils.

Highlights

The aims of the present study were to provide scientific bases for rational use of crop straw to substitute chemical potassium (K) input
The K balance analysis in wheat showed the K was in a deficit state in most no straw return treatments and that the K was in a surplus state in the straw return treatments
After applying straw and fertilizer to the field, the potassium surplus was 24.2–94.3 kg h m−2 under a straw return of 3000 kg h m−2 and was 91.5–154.8 kg h m−2 under a straw return of 6000 kg h m−2. These results indicated that a high amount of straw return provided potassium at levels higher than that absorbed by crops, resulting in increased K surplus in the wheat season