This study aims to clarify the effects of long-term different fertilization on the soil fertility and grain yield under the continuous maize cropping system in coal mining subsidence areas. The key soil factors were determined in the fertilization treatments for the high maize yield. Four treatments were set with no fertilization (CK), nitrogen, phosphorus and potassium fertilizer (NPK), organic manure alone (M), and organic manure combined with chemical fertilizer (MNPK). Soil samples were also collected in the 0-20 cm thickness. A systematic investigation was made to explore the effects of fertilization treatments on the crop yield, contents of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), available potassium (AK), available iron (A-Fe), available manganese (A-Mn), available copper (A-Cu), available zinc (A-Zn), the distribution of aggregates and associated carbon and nitrogen content, as well as the enzyme activities related to carbon cycle. The results showed that the NPK, M and MNPK treatments significantly increased the maize grain yield, especially for M treatment, compared with the CK treatment. M treatment significantly increased the SOM, TN, AK, and A-Mn contents, which increased by 21.50%, 12.50%, 98.37%, and 20.19%, respectively. MNPK treatment was improved the properties of the reclaimed soil. There was the significant increase in the > 2 mm aggregate associated with organic carbon and total nitrogen contents, which were 68.68% and 471.43%, respectively. But the soil A-Cu, and A-Zn contents were reduced by 16.67% and 16.46%, respectively. Moreover, the application of manure (M and MNPK) accelerated the crushing of large macroaggregate (0.25-2 mm), accompanied by the increase of the proportion of silt and clay fraction (< 0.053 mm). In addition, NPK treatment significantly increased the activity of β-glucosidase by 29.17%, but the urease activity was reduced by 29.79%. M and MNPK treatment significantly increased the activities of sucrase, β-glucosidase, urease and alkaline phosphatase, with the increases of 45.87%-73.39%, 54.98%-60.73%, 43.09%-80.32% and 51.52%-54.97%, respectively. Furthermore, the principal component analysis showed that the application of organic manure alone was the better management measure to improve the quality of cultivated land and maintain land productivity in this reclaimed area. The redundant analysis showed that β-glucosidase was a sensitivity index to evaluate the soil fertility, which was contributed 72.40% to the maize grain yield and SOM content. Therefore, the application of organic manure alone can be expected to promote the formation of soil fertility of reclamation under the existing farmland management. The activity of β-glucosidase was enhanced to ultimately improve the crop yield. The effective measure can also be used to maintain the high and stable crop yield for the cultivated land quality in this reclaimed area. The finding can provide a theoretical basis for the improvement of soil and cultivated land quality..
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The aim of this study was to clarify the effects of long-term optimized fertilization (nitrogen reduction) and nitrogen reduction plus film mulching on the characteristics of soil organic carbon (SOC) and its components content, and their contribution to winter wheat grain yield, so as to provide the theoretical support for dryland fertility and crop productivity in the Loess Plateau.
Based on a 7-year location experiment, the undisturbed soil samples from 0-20 cm under different management measures were collected. The variation characteristics of winter wheat grain yield, SOC and its components content were explored, including particulate organic carbon (POC), mineral organic carbon (MOC), light-particulate organic carbon (Light-POC) and heavy-particulate organic carbon (Heavy-POC), and the relationship between SOC and its component content as well as their quantity contribution to the winter wheat grain yield were clarified. The organic carbon components were grouped by continuous physical grouping method, and their contribution for wheat yield was analyzed by redundancy analysis. The experiment set four treatments, including farmer’s practice fertilization (FP), monitoring fertilization (MF), monitoring fertilization plus ridge mulching-furrow planting (RF), and monitoring fertilization plus whole field filming (FH).
The average yield of winter wheat was the lowest under FP treatment, which was 3 070 kg·hm-2. Compared with FP, the wheat yield under MF showed no significant difference, while wheat grain yield under RF and FH could achieve a significant increase by 27.0% and 46.4%, respectively; compared with the initial year of the experiment (2012), the SOC content showed a significant increase under different management measures during seven consecutive years, and the increase rate from low to high was 11.8% (MF), 22.4% (RF), 25.5% (FP), and 36.1% (FH), respectively. The improvement of SOC under MF was the slowest in calcareous cinnamon soil, when MF combining with plastic film mulching showed a significant improvement. The observed SOC components under different treatments showed, compared with FP and MF, RF and FH significantly increased the content of POC, Light-POC and the proportion of Light-POC in SOC. Based on the cooperation of the redundancy analysis, sensitivity index analysis and correlation analysis between SOC and its component, POC contributed the most to the improvement of wheat yield (up to 71.0%) and was the most sensitive to SOC content change and different management measures. Therefore, the improvement of crop yield and soil fertility by FH was mainly achieved by increasing POC content in soil organic carbon.
The monitoring fertilization plus whole field filming treatment was benefit to increase soil organic carbon and active organic carbon content in the cinnamon soil in the southeastern of the Loess Plateau, and achieve a sustainable increase in winter wheat yield.
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