西北黄土丘陵区不同种植年限梯田土壤肥力变化特征及其评价OA

This study aimed to identify the main constraints to crop production in newly constructed high-standard terraces and to elucidate the evolution of soil fertility,thereby providing a scientific basis for efficient utilization of land resources in the regions.Terraced fields with different cultivation durations in the loess hilly region of northwest China were selected as the research objects,with newly built high-standard terraces as a control.Based on national and provincial cultivated land quality monitoring standards,a modified Nemero Comprehensive Index method was applied to evaluate soil fertility,identify key limiting factors in new terraces,and analyze fertility evolution patterns.The results showed that newly constructed terraces exhibited relatively high soil bulk density(graded Ⅳ)and lower organic matter content(grade Ⅳ).Total nitrogen,available phosphorus,and available potassium were all deficient(grade V),while total phosphorus was moderate(graded Ⅲ)and total potassium was relatively high(graded Ⅱ).With increasing cultivation duration,soil bulk density decreased and porosity increased.The activities of key enzymes(sucrase,urease,and alkaline phosphatase)related to carbon,nitrogen,and phosphorus cycling were enhanced.Consequently,the soil organic matter,total nitrogen,available phosphorus,and available potassium in the 0-50 cm soil layer were increased by 3.80 g/kg,0.26 g/kg,9.20 mg/kg,and 21.11 mg/kg,respectively,compared to the newly constructed terraces.The modified Nemero Comprehensive Index classified the soil fertility of newly built terraces as poor(grade Ⅳ,mean index:0.89).With prolonged cultivation,the index gradually increased to 1.28,indicating moderate fertility.In conclusion,soil bulk density represented a structural constraint,while organic matter,total nitrogen,available phosphorus and available potassium were nutrient limiting factors in newly established high-standard terraces.Although soil fertility improved over time,the process remained slow,requiring technical innovation for optimization to accelerate soil fertility enhancement in terraced fields.