Abstract:
Objectives Fluvo-aquic soil is one of the most important agricultural soils in China and is mainly distributed in the producing area for wheat and corn. This study analyzed the evolution of soil nutrient contents, fertility and yield of the fluvo-aquic soils in the past 29 years, providing support for the scientific nutrient management and rational fertilization in fluvo-aquic soil in the future.
Methods There are total of 51 long-term localized monitoring bases for fluvo-aquic soil fertility, distributed in 12 provinces (cities, or autonomous regions) of China. The monitoring period lasted from 10 to 29 years, depending on the establishing time of the bases. The planting methods in the bases included winter wheat-summer maize, spring wheat-summer maize. In this study, the monitoring time was divided into initial monitoring period (1988−1997) , middle monitoring period (1998−2003) and recent monitoring period (2004−2016) . The time dependent changes of soil fertility indexes (organic matter, total nitrogen, available phosphorous, available potassium and pH) and crop yields were analyzed, and the average values of the three monitoring periods were statistically compared. The principal component analysis method was used to search the main indicators for the comprehensive fertility of fluvo-aquic soil.
Results Durring the 29 years round, the contents of organic matter, total N, available P and available K in fluvo-aquic soils showed an overall upward trend, while pH showed a downward trend. The average contents of soil organic matter and total N were significantly increased by 47.1% and 37.8% from the initial to the middle periods of monitoring, and not increased significantly from the middle to percent periods. The average available P was steadily increased by 226% from the initial period to present. The average readily available K contents showed slightly decrease trend in the initial period, and significantly increased by 30.4% from the middle period to present. The soil pH showed a general downward trend, especially from the mid-term (8.14) to present period (7.78). Both the yields of wheat and maize under conventional fertilization showed a significant upward trend with time. The average wheat yield increased significantly by 87.6% from the initial period to the mid-monitoring period. The average yield increase of maize was significant from the initial to the middle stages, with an increase of 111%. Principal component analysis showed that soil total N and organic matter was listed the top two factors that influenced the comprehensive fertility of fluvo-aquic soils.
Conclusions During 10−29 years of conventional fertilization, the single and comprehensive fertility soil in the fluvo-aquic soil area have been significantly improved, and the crop yields are increased significantly as a result. The soil total N and organic matter content are proved to be the main contributors to soil comprehensive fertility, and a downward soil pH exhibits the unbalance in the conventional fertilization. The proportion and amount of nitrogen fertilizer should be properly controlled during the fertilization process.