气候变化对农业产生了重大影响。但大多数研究基于历史气象数据的分析，缺乏与作物生长发育和土壤水分相关联的长期监测。本研究收集了甘肃省农业科学院镇原试验站1957-2020年气象数据和1981-2019年作物生育期数据，并在陇东和宁南开展了相关田间长期试验。研究结果表明，60年来，每10年平均气温增加0.36°C和降水减少11.2mm；1981-2019年的39年间旱地冬小麦田间耗水量平均362.1mm，呈现出每10年减少22.1mm的趋势，但1985-2019年的35年间春玉米耗水量平均405.5mm，保持基本稳定。气候干暖化导致旱地作物生育期发生了明显变化，每10年冬小麦和春玉米生育期缩短5.19天和6.47天，播前推迟3.56天和1.8天，成熟期提前1.76天和5.51天。全膜双垄沟集雨种植使小雨量在垄沟集雨效率达到65.7-92.7%，水分向土壤深层入渗，作物根域水分成倍增加，作物水分满足率提高110-160%，连续15年全膜双垄沟较半膜平作覆盖旱地玉米增产19.87%。旱地玉米群体大小是影响产量和水分利用效率的关键因素，种植密度从3000提高到4500株/亩，玉米产量和水分利用效率增加20.6%和17.4%，从4500提高到6000株/亩再增加12.0%和12.7%。然而，不同降水量地区旱地玉米产量与种植密度均呈现二次曲线关系，曲线性状、最高产量对应的最大密度在地区之间差异很大。在300-500mm年降水量地区，种植密度随降水量的增加而增加，适水种植密度为每1mm降水可种植玉米12株/亩，但超过500mm时种植密度随降水量变化不大。因此，旱地农田抗旱节水应集中在压夏扩秋适水型种植结构建立、垄沟覆盖集雨种植、以水定密适水种植等，以减少气候变化引起的负面影响，增强旱地玉米生产的可持续。

Exploration of soil environmental characteristics governing soil microbial community structure and activity may improve our understanding of biogeochemical processes and soil quality. The impact of soil environmental characteristics especially organic carbon availability after 15-yr different organic and inorganic fertilizer inputs on soil bacterial community structure and functional metabolic diversity of soil microbial communities were evaluated in a 15-yr fertilizer experiment in Changping County, Beijing, China. The experiment was a wheat-maize rotation system which was established in 1991 including four different fertilizer treatments. These treatments included: a non-amended control (CK), a commonly used application rate of inorganic fertilizer treatment (NPK); a commonly used application rate of inorganic fertilizer with swine manure incorporated treatment (NPKM), and a commonly used application rate of inorganic fertilizer with maize straw incorporated treatment (NPKS). Denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene was used to determine the bacterial community structure and single carbon source utilization profiles were determined to characterize the microbial community functional metabolic diversity of different fertilizer treatments using Biolog Eco plates. The results indicated that long-term fertilized treatments significantly increased soil bacterial community structure compared to CK. The use of inorganic fertilizer with organic amendments incorporated for long term (NPKM, NPKS) significantly promoted soil bacterial structure than the application of inorganic fertilizer only (NPK), and NPKM treatment was the most important driver for increases in the soil microbial community richness (S) and structural diversity (H). Overall utilization of carbon sources by soil microbial communities (average well color development, AWCD) and microbial substrate utilization diversity and evenness indices (H’ and E) indicated that long-term inorganic fertilizer with organic amendments incorporated (NPKM, NPKS) could significantly stimulate soil microbial metabolic activity and functional diversity relative to CK, while no differences of them were found between NPKS and NPK treatments. Principal component analysis (PCA) based on carbon source utilization profiles also showed significant separation of soil microbial community under long-term fertilization regimes and NPKM treatment was significantly separated from the other three treatments primarily according to the higher microbial utilization of carbohydrates, carboxylic acids, polymers, phenolic compounds, and amino acid, while higher utilization of amines/amides differed soil microbial community in NPKS treatment from those in the other three treatments. Redundancy analysis (RDA) indicated that soil organic carbon (SOC) availability, especially soil microbial biomass carbon (Cmic) and Cmic/SOC ratio are the key factors of soil environmental characteristics contributing to the increase of both soil microbial community structure and functional metabolic diversity in the long-term fertilization trial. Our results showed that long-term inorganic fertilizer and swine manure application could significantly improve soil bacterial community structure and soil microbial metabolic activity through the increases in SOC availability, which could provide insights into the sustainable management of China’s soil resource.

The aim of drip fertigation is synchronising the application of water and nutrients with crop requirements, and maintaining the proper concentration and distribution of nutrient and water in the soil. The wetting patterns and nutrient distributions under drip fertigation have been proved to be closely related to the fertigation strategies. In order to find out the critical factors that affect the nutrient distribution under different drip fertigaiton strategies, a computer simulation model HYDRUS2D/3D was used to simulate the water and nitrate distribution for various fertigation strategies from a surface point source. Simulation results were compared with the observed ones from our previous studies. A 15° wedge-shaped plexiglass container was used in our experiment to represent one-twenty-fourth of the complete cylinder. The height of container is 40 cm, and the radius is 41 cm. The ammonium nitrate solution was added through a no. 7 needle connected to a Mariotte tube with a flexible hose. The soil water content, nitrate and ammonium concentrations were measured. The comparison of simulated and observed data demonstrated that the model performed reliably. The numerical analysis for various fertigation strategies from a surface point source showed that: (1) The total amount of irrigation water, the concentration of the fertilizer solution and the amount of pure water used to flush the pipeline after fertilizer solution application are the three critical factors influencing the distribution of water and fertilizer nitrogen in the soil. (2) The fresh water irrigation duration prior to fertigation has no obvious effect on nitrate distribution. The longer flushing time period after fertigation resulted in nitrate accumulation closer to the wetting front. From the point of avoiding the possibility of nitrate loss from the root zone, we recommended that the flushing time period should be as shorter as possible. (3) For a given amount of fertilizer, higher concentration of the fertilizer applied solution reduces the potential of nitrate leaching in drip irrigation system. While, lower concentration of the fertilizer solution resulted in an uniform distribution of nitrate band closer to the wetted front.