Preliminary Study On Fertilizer Input Threshold And Reduction Approach In Hubei Province

Since the Ministry of Agriculture and Rural Affairs of the Peoples’s Republic of China formulated“the Action plan for Zero Growth in Fertilizer Use by 2020”in 2015,China’s agricultural fertilizer input has significantly decreased and fertilizer utilization rate has significantly increased.This study was according to the“14th Five Year Plan”planning of plantation in Hubei Province,dividing Hubei Province into five major areas.Based on the crop nutrient demand and soil nutrient supply capacity,this study was aimed to find out the total theoretical demand for chemical fertilizer of major crops（rice,wheat,corn）,oil（i.e.,oilseed rape,peanut）,cotton and linen（i.e.,cotton）,vegetables,fruit trees,tea and other crops in Hubei Province under the current and target production capacity.The theoretical reduction space of chemical fertilizer for major crops in Hubei Province was analyzed based on the current production capacity.By calculating the regional nutrient resources of agricultural wastes（livestock and poultry waste,straw）,we evaluated the land carrying capacity of livestock and poultry waste and the fertilizer reduction potential with the agricultural waste returning to the field.In addition,the potential of fertilizer reduction by adjusting management measures for different crops was explored by using the meta-analysis method with 580 published articles.The main results were as follows:（1）Based on the QUEFTS model,the nutrient requirements of different crops under the current yield level were determined to be 731,400 tN,510,200 tP₂O₅ and 963,100 tK₂O in Hubei Province.The soil nutrient supply capacity of different crops was divided into five grades and the proportion of different soil nutrient supply grades was estimated in five regions.When the nutrient use efficiencies of N,P and K were calculated as 40.2%,18.0%and 50.0%,the theoretical demand for chemical fertilizer of main crops in Hubei Province was 1.98 million tons,and the theoretical reduction space of chemical fertilizer was 33.7%.The theoretical reduction space of fertilizer was 55300 tfor grain crops,331,700 tfor vegetables,20,100 tfor fruit trees and 41,000t for tea trees.When the NUE of N,P and K fertilizer were further increased to 43.0%,20.0%and 60.0%under the premise of constant productivity,the theoretical input of fertilizer to main crops in Hubei Province could be reduced to 1.89 million t,with a decrease of 36.6%.（2）The land carrying capacity index of livestock was the highest in Northern Hubei.The land carrying capacity index of Central Hubei is only 0.17～0.54,indicating that there would be a large space to develop livestock and poultry breeding.In 2019,the nutrient resources of livestock and poultry waste in Hubei Province were 368,900 t N,140,300 tP₂O₅ and 518,400 tK₂O,respectively.Based on 65%of livestock manure and fertilizer returning to the field,the total nutrient returning to the field of livestock and poultry manure would be 239,800 t,91,200 t and 337,700 t,respectively,with the ratio of fertilizer replacement of 17.4%,12.0%and 56.2%,respectively.The total amount of straw resources of main crops in Hubei Province was the highest in Central Hubei and the lowest in Northwest Hubei.At present,the nutrient resources of straw in Hubei province were 310,700 t N,99,800 tP₂O₅ and 683,000 tK₂O,and the proportion of theoretical fertilizer replacement were 22.5%,13.1%and 114.0%,respectively.（3）Based on the collected literature data and meta-analysis method,we further calculated the potential of different agricultural adjustment measures to improve the PFP_N for main crops.Compared with conventional fertilization,application of slow/controlled release fertilizer increased the PFP_N of different crops by 32.3%on average,which was highest in tea（87.0%）and lowest in oilseed rape（8.9%）.The application of organic fertilizer could increase the PFP_N by 40.1%,which was also highest in tea（79.8%）but lowest in soybean（28.2%）.Compared with artificial fertilization,the PFP_N value could be increased by 7.0%by adjusting the depth of N fertilizer.Mechanical sounding fertilization of rice could increase the PFP_N by 19.4%as compared with artificial surface application.Increasing fertilization frequency could increase PFP_N by 21.5%on average,which was highest in cotton（33.4%）.Adjusting cultivation techniques by increasing fertilizer density,the PFP_N value could be increased by 5.5%～27.0%,with an average of 13.6%.In conclusion,the theoretical demand for chemical fertilizer of main crops in Hubei Province is 1.98 million twhen the nutrient use efficiencies of N,P and K fertilizer were40.2%,18.0%and 50.0%,respectively.Compared with the actual fertilizer application amount,the theoretical reduction space was 33.7%.According to the theory of returning major agricultural wastes to the field in Hubei Province,the consumption of nitrogen fertilizer and phosphorus fertilizer could be reduced by 39.9%and 25.1%.The total K amount from agricultural wastes return to the field could theoretically meet the demand for potassium of main crops.For different crops,adjusting fertilizer type could increase PFP_N by 36.6%on average.And adjusting cultivation technology could increase PFP_N by 13.3%,and adjusting cultivation technology could increase PFP_N by 13.6%.