我国主要粮食产区土壤有效态钙镁硫的变化特征及其对作物产量的影响

中量元素钙、镁、硫对农业生产的作用日益突出，研究土壤有效态钙镁硫的变化特征及其对作物产量的影响，可为全国和区域尺度耕地土壤中量元素管理和合理施肥提供理论依据。基于覆盖全国697个耕地质量监测点的监测数据，对比分析2016和2021年全国及六大粮食产区(东北区、华北区、西北区、西南区、长江流域和华南区)的土壤有效态钙镁硫含量的变化特征及其对主要粮食作物产量的影响。与2016年相比，2021年697个监测点的土壤交换性钙和交换性镁平均含量变化不显著，有效硫平均含量显著下降了27.3%，全国交换性钙、交换性镁和有效硫主要与土壤pH和有机质(OM)相关。六大粮食产区土壤有效态钙镁硫含量的年际变化特征有所不同。与2016年相比，2021年东北区交换性钙和镁含量分别显著增加了25.5%和52.4%，主要与pH相关；有效硫含量显著下降了47.8%，主要与速效钾相关。华北区交换性钙含量显著下降了11.8%，主要与pH相关。西北区交换性钙、镁和有效硫含量分别显著下降了64.0%、54.0%和30.4%，钙主要与总钾相关，镁主要与全磷相关，硫与土壤其他理化性质不存在显著相关。西南区有效硫含量显著下降了30.0%，主要与pH和OM相关。长江流域交换性镁和有效硫含量分别显著下降了52.0%和15.7%，主要与pH和OM相关。华南区3种有效态中量元素含量变化不显著，三者主要与pH和OM相关。在全国尺度下，水稻产量与土壤交换性钙和镁含量呈显著正相关，玉米产量与交换性镁和有效硫含量呈显著正相关，小麦产量则与3种中量元素不存在显著相关性；当pH≤7.0时，小麦产量与交换性钙和镁含量呈显著正相关，当pH＞7.0时则不存在显著相关性；无论土壤呈酸性还是碱性，小麦产量均与有效硫含量不存在显著相关性。综上，2016—2021年的5年间，我国耕地土壤交换性钙、镁含量变化不显著，有效硫含量显著降低，这些中量元素主要与土壤pH和OM相关。六大粮食产区中量元素含量变化特征和影响因素及其对主要粮食作物产量的影响存在较大差异，针对性施用中量元素肥料有助于提升区域粮食产量。

Soil available calcium，magnesium and sulfur and their effects on crop yields across major grain production areas of China

The contribution of medium elements，including calcium，magnesium and sulfur，to agricultural productivity was of great importance. The objectives of the present study were to investigate the characteristics of soil exchangeable calcium，exchangeable magnesium，available sulfur and their effects on main crop yields at national and regional scales，so as to provide theoretical basis for the management of medium elements and rational fertilization in cultivated land at national and regional scales.Based on the data from 697 cultivated land quality monitoring sites across China，this research compared and analyzed the characteristics of soil available calcium，magnesium and sulfur and their effects on crop yields at national and six major grain production region scales(the Northeast，North，Northwest，Southwest of China，Yangtze River Basin and the South of China)in 2016 and 2021. Compared to 2016，the average contents of soil exchangeable calcium and exchangeable magnesium did not change significantly，and soil available sulfur content decreased by 27.3% on average at notional scale in 2021. Exchangeable calcium，exchangeable magnesium and available sulfur were mainly related to soil pH and organic matter(OM).The interannual variation characteristics of soil exchangeable calcium，exchangeable magnesium and available sulfur in six major grain production region scales were different. In Northeast China，the contents of soil exchangeable calcium and exchangeable magnesium increased by 25.5% and 52.4% on average，respectively，which was mainly related to pH.Soil available sulfur content decreased by 47.8%，mainly related to available potassium. In North China，soil exchangeable calcium content decreased by 11.8%，which was mainly related to pH. In Northwest China，the contents of exchangeable calcium，exchangeable magnesium and available sulfur decreased by 64.0%，54.0% and 30.4%，respectively. Calcium was mainly related to total potassium，magnesium was mainly related to total phosphorus，while there was no significant correlation between sulfur and soil chemical properties. In Southwest China，soil available sulfur content decreased by 30.0%，mainly related to pH and organic matter. In the Yangtze River Basin，the contents of exchangeable magnesium and available sulfur decreased by 52.0% and 15.7%，respectively，mainly related to pH and organic matter. The contents of three available medium elements did not change significantly in the south of China，and they were mainly related to pH and organic matter. At national scale，the rice yield was positively correlated with soil exchangeable calcium and exchangeable magnesium contents; corn yield was positively correlated with soil exchangeable magnesium and available sulfur contents; there was no significant correlation between wheat yield and three medium elements contents. Wheat yield was positively correlated with soil exchangeable calcium and exchangeable magnesium contents at pH ≤ 7.0. When pH>7.0，there was no significant correlation between wheat yield and soil exchangeable calcium and exchangeable magnesium contents. The wheat yield was not related to soil available sulfur content whether the soil was acidic or alkaline. In summary，the contents of soil exchangeable calcium and exchangeable magnesium did not change significantly，and the available sulfur content decreased significantly across China during the year from 2016 to 2021.The contents of these medium elements were mainly related to soil pH and organic matter. There were significant differences in the variation and influencing factors of soil medium elements，and their impact on main crop yields across six major grain production areas. Optimized medium element fertilization could help improve crop yield at regional scale.