中国主要旱作粮食耕地土壤钾素的时空演变特征

Spatio-temporal Evolution Characteristics of Soil Potassium in Main Dry-farming Grain Arable Land of China

以小麦和玉米等旱作粮食为主的旱地是我国重要的耕地类型,其对国家粮食安全和稳定发挥着极其重要的作用。基于全国耕地质量监测数据库,分析了1988—2007年和2008—2018年间全国及不同区域主要旱作粮食耕地的钾肥投入量、土壤速效钾和缓效钾的时空演变规律,并探讨了土壤速效钾与缓效钾的量化关系。结果表明,1988—2018年全国主要旱作粮食耕地的化肥钾、秸秆钾和总钾的年均投入量(K2O)均保持在较为稳定的水平,年均投入量分别为125 kg·hm–2·a^(–1)、148 kg·hm^(–2)·a^(–1)和273 kg·hm^(–2)·a^(–1)。在不同区域间均呈现出华北和东北的钾肥投入量显著高于其他区域的趋势。与1988—2007年相比,2008—2018年东北、华北、华东和西南的总钾年均投入量增加了4.22%~23.8%,而西北则略有降低。在1988—2018年,全国主要旱作粮食耕地土壤速效钾和缓效钾分别为139 mg·kg^(–1)和665 mg·kg^(–1),与1988—2007年相比,2008—2018年的土壤速效钾和缓效钾分别提高了15.1%和6.72%。在不同区域间,土壤速效钾以西北和东北较高(大于150 mg·kg^(–1)),而华北和华东较低(136~149 mg·kg^(–1)),西南最低(116 mg·kg^(–1)),与1988—2007年相比,2008—2018年华北、华东、西北和西南的土壤速效钾分别提高了15.7%、17.7%、4.16%和34.5%,土壤缓效钾分别增加了8.95%、2.15%、5.71%和4.19%,而东北则略有降低。线性方程表明,随着土壤速效钾的提高,2008—2018年土壤缓效钾的增加量(14.2 mg·kg^(–1))明显高于1988—2007年(7.23 mg·kg^(–1)),同时,不同区域间的拟合方程也表明,随着土壤速效钾的增加,1988—2018年东北、华东和西北的土壤缓效钾增加量明显高于华北。因此,在全国耕地质量监测平台上,与1988—2007年相比,2008—2018年全国和大部分区域主要旱作粮食耕地的土壤速效钾和缓效钾均显著增加。土壤速效钾与缓效钾的线性关系为快速估算缓效钾含量提供了技术参考,但不同试验阶段和区域内拟合方程存在差异,建议不同区域应因地制宜,综合土壤速效钾和缓效钾含量精准划分土壤供钾能力等级,从而为实现藏钾于地的目标奠定基础。

【Objective】Upland soil,as an important type of arable land in China,plays an extremely important role in national food security and stability.Since the reform and opening of China,there were many great changes in farmers'fertilization patterns and planting habits because of soil testing formula fertilization,straw returning and fertilizer reduction to increase efficiency.However,there is still a lack of systematic research on the effects of these changes on the input of potassium(K)fertilizer and soil K in the main dry-farming grain of China.Therefore,the objective of this study was to evaluate the evolution characteristics of K input and fertility in major wheat and/or maize production regions of the whole country,which will clarify the present situation of K fertility and provide certain theoretical guidance for rational application of K fertilizer in different regions.【Method】This study was based on the National Cultivated Land Quality Monitoring database,which was from the Center of Cultivated Land Quality Monitoring and Protection,Ministry of Agricultural and Rural Affairs.Then,the K fertilizer input,soil available K(AK)and slowly available K(SAK)contents were analyzed in five regions of China,which included Northeast of China(NEC),North of China(NC),East of China(EC),Northwest of China(NWC),Southwest of China(SWC)during 1988–2007 and 2008–2018.Meanwhile,the effects of soil AK on SAK were also discussed.【Result】There was a relatively stable chemical K,straw K,and total K fertilizers(K2O)input in the whole country during 1988–2018,with 125 kg·hm^(–2)·a^(–1),148 kg·hm–2·a^(–1),and 273 kg·hm^(–2)·a^(–1),respectively.There was no significant change for K input during 1988–2007 and 2008–2018.In different regions,it was observed that K input in NC and NEC regions was significantly higher than that in other regions.Compared with those of 1988–2007,the total K input in NEC,NC,EC,and SWC regions was increased during 2008–2018 by 4.22%–23.8%,while it was decreased slightly in the NWC region.The AK and SAK of the whole country were 139 mg·kg^(–1)and 665 mg·kg^(–1),respectively.Compared with 1988–2007,the AK and SAK during 2008–2018 increased by 15.1%and 6.72%,respectively.The order of soil AK in the different regions was higher in NWC and NEC regions(more than 150 mg·kg^(–1)),lower for NC and EC regions(136^(–1)49 mg·kg^(–1)),and lowest for SWC region(116 mg·kg^(–1)).During 2008–2018,soil AK in NC,EC,NWC and SWC regions were increased more than during 1988–2007 by 15.7%,17.7%,4.16%and 34.5%,respectively.Also,the soil SAK was increased by 8.95%,2.15%,5.71%and 4.19%,respectively.In the main dry-farming food soils of the whole country,the relationship between soil AK and SAK could be fitted by a linear equation.With the increase in soil AK,the growth rate of soil SAK in 2008–2018(14.2 mg·kg^(–1))was significantly higher than 1988–2007(7.23 mg·kg^(–1)).Meanwhile,the fitting equations among different regions in 1988–2018 also showed that the growth rate of soil SAK in NEC,EC and NWC regions was significantly higher than that in the NC region.【Conclusion】On the long-term monitoring platform of farmlands in China,compared with 1988-2007,the AK and SAK of main dry-farming grain soil were increased significantly during 2008-2018,and there was an increasing trend in most regions.Also,there was a significant linear relationship between soil AK and SAK.These results should provide a technical reference for the rapid estimation of SAK content even though there were differences in the fitting equations during different experimental periods and regions.Thus,it is recommended that different areas should accurately classify soil K supply capacity through AK and SAK by local conditions since it would establish the foundation for realizing the goal of storing K in the soil.