华南区稻田耕地质量空间分布与产能提升潜力

Spatial distribution of cultivated land quality and potential for capacity improvement of paddy fields in South China

为了明确华南区稻田耕地质量空间分布及其提升潜力,为实现华南区水稻高产稳产提供科学依据,本研究基于2017年农业农村部耕地质量监测保护中心在华南区开展的耕地质量区域汇总评价数据,分析华南区稻田耕地质量空间分布情况及其与产能对应关系,并利用随机森林模型明确影响产能提升的主要限制因子。华南区稻田耕地质量等级呈现“中间高,四周低”的空间分布规律;利用半方差函数拟合结果表明,华南区稻田耕地质量等级呈中度空间相关性(R2=0.95),以广东(3.82)最高,海南(5.32)最低。华南区耕地质量评价指标中,土壤养分指标空间分布差异较大,土壤全氮和缓效钾含量空间分布呈强烈的空间相关性,分别呈现“西高东低”和“北高南低”空间分布规律;土壤有机质、有效磷、速效钾含量呈中度空间分布相关性,分别呈现由西向东、由东向西、由北向南不断降低的空间分布趋势;土壤pH整体呈弱酸性(5.40)。土壤物理性状、立地条件、土壤管理情况及土壤健康状况以东部较好,西部较差。华南区稻田耕地质量等级与单产整体呈显著正相关性(R2=0.9140),水稻产量随耕地质量等级提升呈先迅速增加后趋于平缓趋势;华南区稻田耕地质量等级与水稻产量可持续指数呈显著正相关(R^(2)=0.9333)。随机森林模型的重要性分析结果表明,土壤有效磷含量、灌溉能力和土壤有机质含量是影响华南区水稻产量的最关键因素。情景模拟表明,若华南区稻田耕地质量等级分别提升0.5、1.0、1.5个等级,则水稻将增产14.93%、22.39%、29.86%,相当于节约耕地面积31.77万hm^(2)、56.35万hm^(2)、75.95万hm^(2)。华南区稻田耕地质量和产能仍有较大提升潜力,通过提升耕地质量来提升产能对保障粮食安全、促进农业绿色生产具有重大意义。

In order to clarify the spatial distribution and promotion potential of paddy cultivated land quality in South China,and to provide a scientific basis for realizing high and stable rice yield in South China,based on the regional evaluation data of cultivated land quality in South China carried out by the Cultivated Land Quality Monitoring and Protection Center of the Ministry of Agriculture and Rural Affairs of the Perople’s Republic of China in 2017,this study analyzed the spatial distribution of paddy cultivated land quality and its corresponding relationship with productivity in South China.The stochastic forest model was used to identify the main limiting factors that affect the capacity improvement.The spatial distribution law of the quality grade of paddy field in South China was“high in the middle and low around”.The fitting result of semi-variance function showed that the quality grade of paddy field in South China was in moderate spatial correlation(R2=0.95),the highest in Guangdong(3.82)and the lowest in Hainan(5.32).Among the evaluation indexes of cultivated land quality in South China,there was a great difference in the spatial distribution of soil nutrient indexes,and the spatial distribution of soil total nitrogen and slowly available potassium showed a strong spatial correlation,with the spatial distribution law of“high in the west and low in the east”and“high in the north and low in the south”,respectively.The contents of soil organic matter,available phosphorus and available potassium showed moderate spatial distribution correlation,with a decreasing spatial distribution trend from west to east,east to west and north to south,respectively.The overall soil pH was weakly acidic(5.40),with moderate spatial distribution correlation.Soil physical properties,site conditions,soil management and soil health were better in the east and worse in the west.There was a significant positive correlation between the quality grade of paddy field and the overall rice yield in South China(R2=0.9140),and the rice yield increased rapidly at first and then tended to slow down with the improvement of cultivated land quality.There was a significant positive correlation between the quality grade of paddy land and the sustainable index of rice yield in South China(R^(2)=0.9333).The importance analysis of stochastic forest model showed that soil available phosphorus content,irrigation capacity and soil organic matter content were the most important factors affecting rice yield in South China.Scenario simulation showed that if the quality grade of paddy land in South China is improved by 0.5,1.0,1.5 respectively,the yield will increase by 14.93%,22.39%and 29.86%,which is equivalent to saving 317700 hm^(2),563500 hm^(2)and 759500 hm^(2)of cultivated land.There is still great potential to improve the quality and production capacity of paddy farmland in South China.Improving the production capacity by improving the quality of cultivated land is of great significance to ensure food security and promote agricultural green production.