Straw Addition Enhances Crop Yield, Soil Aggregation, and Soil Microorganisms in a 14-Year Wheat-Rice Rotation System in Central China.

Straw return utilizes waste resources to reduce the use of chemical fertilizers worldwide. However, information is still lacking on the relative impact of straw return on soil fertility, the nutrient composition of different soil aggregates, and soil microbial communities. Therefore, this study aimed to understand the effects of different management practices on the crop yield, soil fertility, and soil community composition in a 14-year wheat-rice rotation system. The treatments included a control (without fertilizer and straw addition), chemical fertilization (NPK), straw return without fertilizer (S), and straw addition with chemical fertilizer (NPKS). The results showed that NPKS improved the wheat and rice yield by 185.12% and 88.02%, respectively, compared to the CK treatment. Additionally, compared to the CK treatment, the N, P, and K contents of the wheat stem were increased by 39.02%, 125%, and 20.23% under the NPKS treatment. Compared to the CK treatment, SOM, TN, TP, AN, AP, AK, CEC, AFe, AMn, ACu, and AZn were increased by 49.12%, 32.62%, 35.06%, 22.89%, 129.36%, 48.34%, 13.40%, 133.95%, 58.98%, 18.26% and 33.33% under the NPKS treatment, respectively. Moreover, straw addition promoted the creation and stabilization of macro-aggregates in crop soils. The relative abundance of macro-aggregates (0.25-2 mm) increased from 37.49% to 52.97%. Straw addition was associated with a higher proportion of aromatic and carbonyl carbon groups in the soil, which, in turn, promoted the formation of macro-aggregates. Redundancy analysis showed that straw return significantly increased the microbial community diversity. These findings demonstrate that straw addition together with chemical fertilizer could increase the crop yield by improving soil fertility, soil aggregate stability, and the diversity of fungi.

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

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.

Joint analytical hierarchy and metaheuristic optimization as a framework to mitigate fertilizer-based pollution.

The emission of nitrogenous pollution from agricultural lands in form of ammonia volatilization, leaching, runoff, N2O emissions, etc. is still a serious challenge to which agricultural sector faces. In this context, a vast number of decision support systems have been developed and tested to find the best nitrogen application rate. These models are highly dependent on crop simulation models, mathematical and regression models, evolutionary algorithms and artificial intelligent, GIS-based models, etc., while in most cases have ignored to be interfered with regional and national regulations established by experts in the field. In this study, a new framework combining analytical hierarchy (AHP)/modified AHP methods (MAHP) plus metaheuristic optimization techniques has been suggested to find the best nitrogen application rate considering regional capacities and requirements. To reach the objectives of the present study a three yield field experiment was conducted upon which crop yield, nitrogen use efficiency, nitrogen uptake, soil nitrate, ammonia volatilization, N2O emissions, and N leaching were monitored or measured. Using the results from the field experiments and a survey from local experts, the models were developed. AHP-assisted optimization model could cause some biases in the final results due to its intrinsic nature which avoids direct pairwise comparison among indicators (so called sub-criteria) under two different main-criteria. On the contrary, MAHP-assisted model could well reflect the concerns of experts and notably decrease hotspot pollution. Such decision support system can satisfy both farmers and environmentalists' need because of the created high profit and low environmental pollution, while saving resources and ensuring a sustainable production system.

Cadmium accumulation, availability, and rice uptake in soils receiving long-term applications of chemical fertilizers and crop straw return.

Fertilization and straw return have been widely adopted to maintain soil fertility and increase crop yields, but their long-term impacts on the accumulation and availability of cadmium (Cd) in paddy soils are still unconfirmed. Therefore, this study was undertaken in central China to investigate the accumulation, availability, and subsequent uptake of Cd by rice (Oryza sativa L.) in two adjacent field trials (P1 and P2, lasting for 10 and 12 years, respectively) under long-term straw return or in combination with chemical fertilizers. Obvious Cd accumulation, probably due to the notable Cd input from irrigation and traffic exhaust in the bulk soil (0-20 cm) of P1, was observed. The bulk soil of P2 received homogeneous straw return and chemical fertilizers, as did that of P1; however, the P2 soil almost showed Cd balance. Long-term straw return increased the portion of soil DTPA-extractable Cd to the total pool for both sites, but only P1 showed significant differences when compared to the controls. However, the highest Cd concentrations and the maximum bioconcentration factors in rice straw and grain were obtained using solo application of chemical fertilizers at both sites. Continuous additional applications of crop straw, in contrast, resulted in slightly decreased Cd uptake in rice straw, but not in grain. These findings demonstrate that neither long-term straw return nor fertilization leads directly to notable Cd accumulation, but that the promotion effects of long-term chemical fertilizer applications on Cd uptake in rice need more attention.