Synergetic effects of oasis farmland nitrogen and phosphorus utilization on production, economic, and environmental benefits

In 2020, the Xinjiang Production and Construction Corps (XPCC), as a typical representative of oasis agriculture in Northwest China, produced 2.41 million tons of grain, with a total planting area of 14.15 million hectares. Cotton, corn, and wheat accounted for 61.14%, 8.25%, and 7.98% of the total planting area respectively. The systematic evaluation of nitrogen and phosphorus utilization efficiency in regional farmland and analysis of nutrient management issues have become important topics for sustainable agricultural development. Therefore, this paper focuses on the agricultural production system in the XPCC, aiming to elucidate the characteristics of nitrogen and phosphorus nutrient flow in farmland and calculate the surplus and efficiency of nitrogen and phosphorus nutrients from 2000 to 2020. Additionally, the Spearman correlation analysis method was used to explore the synergistic relationship between nutrient management and production levels, economic benefits, and environmental benefits. A comparative country analysis was carried out. The results showed that: 1) From 2000 to 2020, farmland nitrogen input and output in the XPCC both showed an initial increase followed by a stabilization trend. In 2020, farmland nitrogen input and output were 4.58×10⁸ kg and 2.49×10⁸ kg respectively. Chemical fertilizer was the main source of nitrogen input, accounting for 87.37% of total nitrogen input. Straw, grains, and ammonia volatilization were the major pathways for nitrogen output, accounting for 42.89%, 24.63%, and 20.16% of total nitrogen output respectively. Farmland phosphorus input exhibited an initial increase followed by a stabilization trend, while phosphorus output showed a continuous increase trend. Farmland phosphorus input and output were 1.35×10⁸ kg and 0.68×10⁸ kg respectively. Chemical fertilizer accounted for 94.1% of total phosphorus input. Grains and straw were the primary pathways for phosphorus output, accounting for 70.43% and 28.31% of total phosphorus output respectively. The farmland nitrogen surplus showed a fluctuating increase trend from 2000 to 2020, increasing from 91.90 kg/ha in 2000 to 147.54 kg/hm² in 2020, representing a 61% increase. The phosphorus surplus exhibited an initial increase followed by a decreasing trend, rising from 26.57 kg/hm² in 2000 to 61.26 kg/hm² in 2015 and then declining to 47.61 kg/hm² in 2020. The relatively high farmland nitrogen and phosphorus surpluses in the XPCC posed a high risk of environmental pollution. Farmland nitrogen and phosphorus utilization efficiency from 2000 to 2020 showed stable fluctuations, ranging from 34.33% to 44.05% for nitrogen and from 39.25% to 49.54% for phosphorus. Nitrogen and phosphorus utilization efficiency were relatively low, indicating room for improvement. 2) There was a trade-off effect between farmland nutrient utilization and production levels, economic benefits and environmental benefits in the XPCC, while there was a synergistic effect between production levels and economic benefits. The high yield of agricultural mechanization production in the XPCC was at the expense of nutrient loss and environmental pollution. 3) The nutrient utilization level in developed countries was relatively high, which synergistically promoted the production levels and economic benefits without sacrificing environmental benefits. However, the nutrient utilization in Central Asian countries and the XPCC presented a trade-off effect with the production levels and economic benefits. In conclusion, two recommendations were proposed for farmland nutrient management. Firstly, based on the farms, clear reward and punishment systems should be established, nutrient accounting and management were initiated from high-standard farmland, and promoted smart agricultural technology to control fertilizer and water. The science and technology backyard could be employed to lead and demonstrate nutrient management, facilitating technology dissemination and application. Secondly, regional crop and livestock structure and layout should be optimized, sufficient equipment was provided for manure fermentation and fertilizer application, production mechanization, and the use of chemical fertilizers reduced.