Temporal And Spatial Variation In Potassium Nutrient Surplus And Deficit Balance In Farmland Of China

Potassium?K?resources are deficient in China.Rational utilization of potash is significant for food security,agricultural product quality and soil productivity.Understanding soil K surplus and deficit balance status in China is crucial for the efficient use of potash resources.This study established the soil K surplus and deficit balance model and the K surplus and deficit balance parameters database based on the previous research using statistical data and literature.The structural composition of soil potassium input,output and K surplus and deficit balance from 1980 to 2015,and the temporal and spatial changes at regional and provincial level were analyzed.The results were showed as follows: 1)The average K input from 1980 to 2015 in China was 14.95 million tons K₂O(146.92 kg K₂ O ha^-1yr^-1).At national level,the K input increased obviously with time which was 84.25,139.35,183.32 and 203.33 kg K₂ O ha^-1yr^-1 in 1980 s,1990s,2000 s and 2010 s,respectively with the average annual increment of 0.48 Mt K₂O(3.94 kg K₂ O ha^-1yr^-1).At regional level,the average K input from 1980 to 2015 in the northeast?NE?,north central?NC?,northwest?NW?,the middle and lower reaches of the Yangtze River?MLYR?,southeast?SE?and southwest?SW?was 68.04,157.16,92.14,184.37,310.68 and 197.00 kg K₂ O ha^-1yr^-1,respectively.At provincial level,the average annual increment from 1980 to 2015 was larger in Fujian,Guangdong,Guangxi and Hainan province(9.02-12.91 kg K₂ O ha^-1yr^-1),which were all located in the SE.The average annual increment was smaller in Heilongjiang,Inner Mongolia and Qinghai province(0.50-1.08 kg K₂ O ha^-1yr^-1).2)Potassium input mainly consisted of three components: chemical fertilizer,organic manure and other K input resources?deposition,irrigation and seeds?,which accounted for 32.8%?4.91 Mt K₂O?,59.2%?8.85 Mt K₂O?and 8.0%?1.19 Mt K₂O?of total input,respectively during 1980 to 2015.The proportions of chemical fertilizer and organic manure were 10.2,27.0,38.2,44.5 % and 75.7,64.5,55.3,49.6% in 1980 s,1990s,2000 s and 2010 s,respectively.3)The average K output from 1980 to 2015 in China was 14.78 Mt K₂O(146.11 kg K₂ O ha^-1yr^-1).At national level,the K output increased obviously with time which was 108.41,145.27,162.01 and 183.84 kg K₂ O ha^-1yr^-1 in 1980 s,1990s,2000 s and 2010 s,respectively,with the average annual increment of 0.38 Mt K₂O(3.01 kg K₂ O ha^-1yr^-1).At regional level,the average K output from 1980 to 2015 in the NE,NC,NW,MLYR,SE and SW was 89.41,155.91,78.44,207.17,211.45 and 189.82 kg K₂ O ha^-1yr^-1,respectively.At provincial level,the average annual increment from 1980 to 2015 was larger in Hubei province(5.82 kg K₂ O ha^-1yr^-1)which was smaller in Heilongjiang,Beijing,Shanxi,Tibet and Qinghai province(0.65-1.36 kg K₂ O ha^-1yr^-1),while it decreased by 0.53 kg K₂ O ha^-1yr^-1 in Zhejiang province.4)The major components of potassium output included two parts: crops removal and loss.The average proportion of crops removal and loss accounted for 99.0%?14.63 Mt K₂O?and 1.0%?0.15 Mt K₂O?of total K output,respectively.5)The average K surplus and deficit balance from 1980 to 2015 in China was 0.17 Mt K₂O(0.81 kg K₂ O ha^-1yr^-1).At national level,the K surplus and deficit balance increased slowly and steadily over time which was-24.17,-5.92,21.31 and 19.50 kg K₂ O ha^-1yr^-1 in 1980 s,1990s,2000 s and 2010 s,respectively with the average annual increment of 0.1 Mt K₂O(0.93 kg K₂ O ha^-1yr^-1).At regional level,the average K surplus and deficit balance from 1980 to 2015 in the NE,NC,NW,MLYR,SE and SW was-21.37,1.25,13.70,-22.79,99.22 and 7.18 kg K₂ O ha^-1yr^-1.At provincial level,the average annual increment from 1980 to 2015 was larger in Guizhou,Sichuan and Yunnan Province(6.72-7.61 kg K₂ O ha^-1yr^-1)which was smaller in Hebei,Qinghai,Gansu,Inner Mongolia,Ningxia,Xinjiang and Jiangsu Province(0.06-1.97 kg K₂ O ha^-1yr^-1)and were mainly located in the NW.6)The average K use efficiency?KUE?from 1980 to 2015 in China was 1.04.At national level,the KUE decreased significantly with time from high level?1980s and 1990s?to moderate levels?2000s and 2010s?which was 1.27,1.04,0.88 and 0.90 in 1980 s,1990s,2000 s and 2010 s,respectively.