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The Olsen phosphorus (Olsen-P) concentration of soil is generally a good indicator for estimating the bioavailability of P and environmental risk in soils. To maintain soil Olsen-P at adequate levels for crop growth and environmental sustainability, the relationship between soil Olsen-P and the P budget (the P input minus the output) as well as the variations of soil Olsen-P and P budget were investigated from three long-term (22 years) experiments in China. Five treatments were selected: (1) unfertilized control (CK); (2) nitrogen and potassium (NK); (3) nitrogen, phosphorous, and potassium (NPK); (4) nitrogen, phosphorous, potassium and straw; (5) nitrogen, phosphorous, potassium and manure. The results showed that without P fertilizers (CK, NK), there was a soil P deficit of 75–640 kg ha-1, and the lowest P deficit (mean of CK and NK) was in Eutric Cambisol. Soil Olsen-P decreased by 0.11–0.39 mg kg-1 year-1 in the order of Luvic Phaeozems > Eutric Cambisol > Calcaric Cambisol. Soil Olsen-P and the P deficit had a significantly (P<0.01) positive linear relationship. For every 100 kg of P ha–1 of deficit, soil Olsen-P decreased by 0.44–9.19 mg kg–1 in the order of Eutric Cambisol > Luvic Phaeozems > Calcaric Cambisol. Under the P fertilizer treatments (NPK, NPKS, and NPKM), soil Olsen-P showed an obvious surplus (except the NPK and NPKS in Luvic Phaeozems) of 122–2190 kg ha-1, and the largest P surplus was found under the NPKM treatment at each site. The relation between soil Olsen-P and the experimental years could be simulated using quadratic equation of one unknown in Calcaric Cambisol for the lower P input after 14 years of fertilization. And soil Olsen-P increased by 1.30–7.69 mg kg-1 year-1 in the order of Luvic Phaeozems > Eutric Cambisol. The relation between soil Olsen-P and the P surplus could be simulated by a simple linear equation except under NPK and NPKS in Luvic Phaeozems. With 100 kg ha-1 P surplus, soil Olsen-P increased by 3.24–7.27 mg kg-1 in the order of Calcaric Cambisol (6.42 mg kg-1) > Eutric Cambisol (3.24 mg kg-1). In addition, the change in soil Olsen-P with a 100 kg P ha-1 surplus (soil Olsen-P efficiency) was affected by the soil organic matter (SOM), pH, and CaCO3 content, etc. In the practice of fertilization, it's not necessary to increase the amount of P fertilizers, farmers should take measure to solve the local problem, for adjust the soil pH of Eutric Cambisol and Calcaric Cambisol, and apply more nitrogen in Luvic Phaeozems. In the area of serious soil P surplus, it is encouraged to stop applying P fertilizers for a few years to take advantage of soil accumulated P and make the high Olsen-P content decrease to a reasonable level. [ABSTRACT FROM AUTHOR]

Purpose: Phosphorus (P) fertilizer has been widely applied to improve crop yields in the North China Plain; however, most of applied P fertilizer is disabled due to the strong sorption/fixing processes in the soil. This study evaluates the change characteristics of soil properties on different textural soils and their relationships with the P adsorption and desorption under long-term fertilization to do a favor to make strategies for improving the P availability of the soil.Materials and methods: Five textural fluvo-aquic soils including gritty sand, silt sand, sandy loam, medium loam, and light clay were investigated in a 27-year (1990-2017) long-term fertilization experiment at Zhengzhou (Henan province) of China. Soil samples were collected in 1990, 1999, and 2017 at 0-20 cm to measure soil properties (i.e., soil mechanical composition) and P adsorption and desorption characteristics.Results and discussion: The clay and silt contents decreased and sand content increased in the light clay soil with the cultivation years, the opposite situation for the gritty sand and silt sand soils. The contents of total P, Olsen-P, and organic matter (SOM) in the five textural soils were increased over time. There were stronger P absorption capacity and weaker desorption ability for the light clay soil relative to others, which was reflected in the largest P maximum buffer capacity (MBC) and the lowest β value; however, the P adsorption capacity tended to decrease over time for the light clay soil. Clay and silt fractions were positively correlated with MBC, while negatively correlated with β (P < 0.01); similar disciplines were found in the contents of SOM, total iron (Fe), and free Fe oxides (FeDCB).Conclusions: The mechanical composition of five textural fluvo-aquic soils changed to some extent under the long-term cultivation, thereby improved P absorption and desorption capacity. The clay and silt fractions as well as SOM and FeDCB contents were the major factors for the P adsorption, but sand content was the major factor for the P desorption. [ABSTRACT FROM AUTHOR]

Combining organic materials with chemical fertilizers is gradually becoming the primary fertilization strategy in China for increasing soil phosphorus (P) concentration; however, the relationships between soil available P, P composition and phosphatase activities in treatments with long-term crop straw or animal manure combined with chemical NPK fertilizers are not fully understood. In this study, a field fertilization experiment was conducted in a light sandy loam soil from the Huang-Huai-Hai Plain of China to determine the variation in soil available P, P composition and phosphatase activities with 23 years of continuous application of maize straw or cattle manure in combination with chemical fertilizers at the depth of 0–20 cm, with special attention paid to their relationships. The experiment was arranged in a randomized block design with three replications for each treatment, including the unfertilized control (CK), chemical nitrogen (N) with phosphorus (P) and potassium (K) (NPK), NPK plus maize straw (NPKS), and NPK plus cattle manure (NPKM). Results indicated that all fertilization treatments significantly increased soil P concentration and crop yields. Among the fertilization treatments, NPKM treatment showed the significantly highest total P and available P concentrations, while no significant difference in either wheat or maize yield between NPK, NPKS and NPKM treatments was found. Compared to the application of chemical NPK fertilizers alone, the NPKS treatment significantly increased soil organic P, pyrophosphate and orthophosphate concentrations, as well as soil phosphatase activities. The increase in orthophosphate concentration under the NPKS treatment may be associated with the hydrolysis of organic P and pyrophosphate catalyzed by acid phosphomonoesterase (AcP), phosphodiesterase (PD) and inorganic pyrophosphatase (IPP), which was conducive to keeping soil available P concentration under NPKS treatment at an appropriate level that could not only satisfy crop P demand but also have no negative impacts on the environment. However, the increase of orthophosphate and available P concentrations under NPKM treatment may be primarily related to the manure P inputs, and although NPKM treatment significantly increased soil inorganic P concentration in comparison to other fertilization treatments, it also increased the risk of P leaching. Overall, from the perspective of P nutrient management, our results suggest that NPKS treatment might be an effective long-term fertilization practice in the light sandy loam soil of Huang-Huai-Hai Plain of China. [ABSTRACT FROM AUTHOR]

Abstract: Efficiency of fertilizer N is becoming increasingly important in modern agricultural production owing to increasing food requirement and growing concern about environments. However, there is almost no study regarding its long-term efficiency in wheat and maize cropping systems. Long-term (15 years) experiments involving wheat (Triticum aestivum L.) and maize (Zea mays L.) rotations at five field sites with various soil and climate characteristics in China were used to determine the nitrogen (N) efficiency, including the physiological efficiency, recovery efficiency and N mass balance of soil–plant systems in response to different fertilization treatments. The present study consisted of nine treatments: unfertilized, N, phosphorus, potassium, straw and manure or their combinations. The contribution of N fertilizers to wheat yield was higher than to maize and suggested that wheat could be given priority over maize when determining N application rates. Uptake of 1kg N produced 35.6kg of wheat grain and 39.5kg of maize grain. The deficit of N in soils without applied N ranged from 40 to 103kgNha−1 year−1, while N surpluses in soils with applied N fertilizers ranged from 35 to 350kgNha−1 year−1. The apparent accumulated N recovery efficiency (NREac) varied widely from 4% to 90%: unbalanced fertilization and other soil limiting factors (such as aluminium toxicity) were associated with low NREac. In the treatments of combination of N, phosphorus and potassium with normal application rates, the average of NREac in four out of five sites reached 80%, which suggested that best management of N fertilizers could recover most of N fertilizers applied to soils. The results will be helpful to understand the long-term fate of N fertilizers and to optimize the N fertilization for agricultural practices and environment protection. [Copyright &y& Elsevier]

RothC and DNDC, two process-based agroecosystem models widely utilized for quantifying soil carbon (C) sequestration, were tested against datasets of soil organic carbon (SOC) measured in two long-term experiments with winter wheat-summer maize rotation at field soils in North China. In the study, the two models were utilized in conjunction in three modes, i.e., using DNDC alone, using RothC driven by soil C inputs of measured crop residue, and using RothC driven by soil C inputs derived from DNDC simulations. In general, results from the three ways of simulations were in agreement with the measured SOC dynamics for the two experimental sites with varied treatments. However, discrepancies in the results revealed the differences between the two models regarding their functionality. The simulations with RothC driven by the measured crop residue as C input produced the best results on SOC dynamics in comparison with observations. Results from the simulations with DNDC alone were less correlated to observations mainly due to the approximation of the modeled amount of crop residue. Due to the same reason, the simulations with RothC but driven by DNDC-modeled crop residue poorly fit to observations. The results conclude that given the similarity between RothC and DNDC regarding their routines modeling SOC transformations it is crucial for improving the models’ performance to provide accurate C input data (mainly crop residue) to the SOC turnover modules in the models. [ABSTRACT FROM AUTHOR]

Abstract: Long-term (over 15 years) winter wheat (Triticum aestivum L.)–maize (Zea mays L.) crop rotation experiments were conducted to investigate the accumulation of phosphorus (P) at five sites differing geographically and climatically in China. The results showed that, in soils without P added, the concentration of soil P extracted by 0.5molL−1 NaHCO3 at pH 8.5 (Olsen-P) decreased with cultivation time until about 3mgkg−1, afterwards it remained constant. The trend of decrease in Olsen-P in soils without P added could be described by an exponential function of time. The concentration of Olsen-P in soils with P fertilizers increased with cultivation time and the model of accumulation of Olsen-P in soils could be described using P application rate, crop yield and soil pH. The accumulation rate of Olsen-P in the long-term wheat–maize crop rotation experiments was 1.21mgkg−1 year−1 on average. If the target yield of wheat and maize is 10tonha−1 in the soil with pH 8, the increasing rates of Olsen-P in soils as estimated by the model will be 0.06, 0.36, 0.66, 0.95, 1.25 and 1.55mgkg−1 year−1 when P application rates are 30, 40, 50, 60, 70 and 80kgPha−1 year−1, respectively. The models of accumulation of Olsen-P in soils were validated independently and could be used for the accurate prediction of accumulation rate of Olsen-P in soils with wheat–maize rotation systems. Also the application of the model was discussed for best management of soil P in agricultural production and environment protection. [Copyright &y& Elsevier]

• Soil pH determines fertilization strategy and fungal community response. • Long-term inorganic fertilization can achieve high crop yield in alkaline soils. • Acidic soil productivity can be maintained by inorganic-organic fertilization. • Mortierella and Pseudaleuria were enriched by inorganic-organic fertilization. Agricultural fertilization plays a crucial role in crop production, and the fungal communities catalyze transformation of soil nutrients in support of crop production. However, it remains controversial about the optimal strategy for fertilizer inputs and the adaptive mechanisms of fungal communities across China. By using seven long-term field fertilization experiments in China, we analyzed crop yields, soil properties and fungal communities in soils that were treated for > 25 years with no fertilizer (control), inorganic fertilizers (NPK) and organic-inorganic fertilizers (NPKM). Long-term NPK resulted in significant acidification up to a decline by 1.20 pH units, while NPKM prevented acidification and increased pH up to 6.39 in three acidic soils with pH < 5.70. NPKM increased crop yields by 1.19–8.72 folds in acidic soils, being significantly higher than NPK. Specific saprotroph Mortierella and Pseudaleuria in acidic soils were exclusively enriched by NPKM. Soil pH was directly related to the abundance of Mortierella , and the enrichment of Mortierella species further caused a positive direct effect on crop yield. In four alkaline soils with pH > 8.11, both NPK and NPKM led to only marginal decline of soil pH, and NPK and NPKM showed comparable crop yields. Some members of Ascomycota in alkaline soils were both enriched by NPKM and NPK. Soil available P and C:N ratio, rather than pH, directly or indirectly affect crop yield in alkaline soils. High crop yield can be achieved by the sole use of inorganic fertilizers in alkaline soils, but acidic soil productivity should be maintained by organic amendment to counteract acidification by inorganic fertilization. Our study advances a mechanistic understanding for optimizing fertilization strategies towards sustainable agriculture under increasingly intensified fertilizer inputs. [ABSTRACT FROM AUTHOR]

Background: The carbon sequestration potential is affected by cropping system and management practices, but soil organic carbon (SOC) sequestration potential under fertilizations remains unclear in north China. This study examined SOC change, total C input to soil and, via integration of these estimates over years, carbon sequestration efficiency (CSE, the ratio of SOC change over C input) under no fertilization (control), chemical nitrogen fertilizer alone (N) or combined with phosphorus and potassium fertilizers (NP, NK, PK and NPK), or chemical fertilizers combined with low or high (1.5×) manure input (NPKM and 1.5NPKM)., Results: Results showed that, as compared with the initial condition, SOC content increased by 0.03, 0.06, 0.05, 0.09, 0.16, 0.26, 0.47 and 0.68 Mg C ha -1 year -1 under control, N, NK, PK, NP, NPK, NPKM and 1.5NPKM treatments respectively. Correspondingly, the C inputs of wheat and maize were 1.24, 1.34, 1.55, 1.33, 2.72, 2.96, 2.97 and 3.15 Mg ha -1 year -1 respectively. The long-term fertilization-induced CSE showed that about 11% of the gross C input was transformed into SOC pool., Conclusion: Overall, this study demonstrated that decade-long manure input combined with chemical fertilizers can maintain high crop yield and lead to SOC sequestration in north China. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)