长期施肥对春玉米田土壤呼吸及碳平衡的影响研究

为探讨不同施肥方式下农田碳平衡规律,研究农田排放到大气CO₂的“源”、“汇”特征,依托39 a肥料定位试验测定了秸秆和氮磷肥配施（SNP）、农家肥和氮磷肥配施（MNP）、单施农家肥（M）、氮磷肥配施（NP)、单施氮肥（N）和不施肥（CK）等6种不同施肥方式下西北黄土旱塬春玉米拔节期到成熟期的土壤呼吸。结果表明：长期不同施肥方式能够影响春玉米农田土壤CO₂排放,不同生育时期排放特征不同,呈先升高后下降趋势,即开花期达到排放高峰,SNP、MNP和M的CO₂排放通量分别达到3 650.54、2 980.50 mg·m^-2·h^-1和2 167.61 mg·m^-2·h^-1,与CK相比,分别增加了340.32%、259.51%和161.45%。不同施肥处理间表现为SNP>MNP>M>NP>N>CK。整个测定时期内土壤CO₂平均排放速率表现为SNP>MNP>M>NP>N>CK,土壤呼吸中根系呼吸的贡献率波动在31%~77%之间。6种不同施肥处理农田土壤均表现为大气CO₂排放的“汇”,不同施肥处理农田碳汇强弱不同,表现为SNP>M>MNP>NP>N>CK。     

平衡施肥对马铃薯-大豆套作系统中作物产量的影响

根据西北一熟制灌区土壤养分条件以及马铃薯-大豆系统中作物养分吸收互补的特点,选用马铃薯品种费乌瑞它和大豆品种冀豆12作为试验材料,设置3重复随机区组试验,小区处理最优施肥(OPT:N、P、K分别为180、135、135 kg hm~(–2))、最优减N(OPT-N)、最优减P(OPT-P)、最优减K(OPT-K)、最优减1/3N(OPT-1/3N)、最优增1/3N(OPT+1/3N)、最优减1/3P(OPT-1/3P)、最优增1/3P(OPT+1/3P)、最优减1/3K(OPT-1/3K)和不施肥(CK)10个处理。通过2012—2013连续2年大田试验,系统分析N、P、K对套作马铃薯及套作大豆产量及产量构成因素的影响。结果表明,OPT-N处理与OPT处理套作马铃薯产量差异最大(11 653.86 kg hm~(–2));OPT-P处理与OPT处理套作大豆产量差异最大(751.55 kg hm~(–2)),差异均达到显著水平(P0.05),说明影响套作马铃薯、套作大豆产量的最大的因素分别是N和P。随N水平递增,套作马铃薯产量呈现递增的趋势,OPT+1/3N处理产量最高为50 231.85 kg hm~(–2);套作大豆产量则呈现先增后减的趋势,OPT处理产量最高为3373.55 kg hm~(–2),方差分析表明,OPT和OPT+1/3N各处理套作马铃薯产量差异不显著,OPT-1/3N、OPT、OPT+1/3N各处理套作大豆产量差异不显著。随P素水平增加,套作马铃薯和套作大豆产量均呈现增加趋势,OPT+1/3P处理下套作马铃薯、套作大豆产量均最高,分别为52 430.03 kg hm~(–2)和3637.13 kg hm~(–2),同样在OPT+1/3P处理下,套作马铃薯平均单薯最重,套作大豆有效荚数、每荚粒数及单株粒数均最高,2年平均分别为185.13、74.24、1.87和139.15 g。综合考虑薯豆套作产量效应及养分利用效率,OPT施肥方案中,N适宜,P偏低,K偏高。     

Planting density and sowing proportions of maize–soybean intercrops affected competitive interactions and water-use efficiencies on the Loess Plateau,China

In field trials on the Loess Plateau, China, in 2012–13, maize (Zea mays L.) and soybean (Glycine max L.) were sole cropped and intercropped at three densities and with three sowing proportions. Maize was generally more growth efficient for biomass accumulation than soybean during the entire growth interval, as assessed using the relative efficiency index (REI_c). However, most of sowing proportion at each density displayed a trend of decreased growth with development. Throughout the growth period, the dry matter production and leaf area index (LAI) of maize increased as the plant density increased irrespective of whether it was grown as a sole crop or as an intercrop. However, the effect of increasing cropping density was less obvious for soybean. The LAI values of the sole crop treatment for both maize and soybean were greater than that of the intercropping system, indicating that the presence of maize and soybean together suppressed the respective growth of the two crops. At the final harvest, land equivalent ratios (LER) of 0.84–1.35 indicated resource complementarity in most of the studied intercrops. Complementarity was directly affected by changes in plant densities; the greatest LER were observed in 2 rows maize and 2 rows soybean intercrops at low density. The water equivalent ratio (WER), which characterized the efficiency of water resource use in intercropping, ranged from 0.84 to 1.68, indicating variability in the effect of intercropping on water-use efficiency (WUE).     

Temperature sensitivity of heterotrophic soil CO2 production increases with increasing carbon substrate uptake rate

Temperature profoundly affects saprotrophic respiration rates, and carbon quality theory predicts that the rates' temperature sensitivity should increase as the quality of the carbon source declines. However, reported relationships between saprotrophic respiration responses to temperature and carbon quality vary widely. Some of this variability may arise from confounding effects related to both substrate quality and substrate availability. The importance of these variables, as well as substrate diffusion and uptake rates, for the temperature sensitivity of saprotrophic respiration has been validated theoretically, but not empirically demonstrated. Thus, we tested effects of varying substrate uptake rates on the temperature sensitivity of organic carbon degradation.For this purpose we created a model system using the organic layer (O-horizon), of a boreal forest soil, specifically to test effects of varying monomer uptake and release rates. The addition of both monomers and polymers generally increased the temperature sensitivity of saprotrophic respiration. In response to added monomers, there was a linear increase in the temperature sensitivity of both substrate-induced respiration and the specific growth rate with increasing rate of substrate uptake as indicated by the CO₂ production at 14 °C. Both of these responses diverge from those predicted by the carbon quality theory, but they provide the first empirical evidence consistent with model predictions demonstrating increased temperature sensitivity with increased uptake rate of carbon monomers over the cell membrane. These results may explain why organic material of higher carbon quality induces higher temperature responses than lower carbon quality compounds, without contradicting carbon quality theory.     

覆膜与钾肥互作对油葵产量和钾肥利用效率的影响

为了获得半干旱区油葵高产高效的最佳栽培措施，2015-2017年以油用向日葵（陇葵杂3号）为材料，研究3个覆膜栽培条件及4个钾肥水平条件下的油葵产量和钾肥利用效率。3个栽培模式分别为露地、全膜双垄沟播、全膜双垄沟播+补灌。4个钾肥水平分别为0、48、84和120kg/hm2。调查籽粒产量和干物质积累，计算钾肥吸收利用，结果表明：覆膜与钾肥互作显著影响籽粒产量、干物质积累和钾肥利用效率，且两者互作效应显著；栽培方式对上述三者的影响均表现为全膜双垄沟播+补灌＞全膜双垄沟播＞露地，且差异显著；与露地相比，全膜双垄沟播+补灌和全膜双垄沟播处理油葵籽粒产量、钾肥利用效率分别显著提高了170.1%和103.9%、184.3%和143.7%。各施钾处理籽粒产量和器官干物质积累量均显著高于不施钾，表现为K120＞K84＞K48＞K0，施钾处理间除120与K84外，籽粒产量和干物质积累量差异显著。钾肥偏生产力随施钾量的增加而下降，钾肥农学效率和钾肥利用效率则先升高后降低，以84kg/hm2时钾肥农学效率和钾肥利用效率最大。油葵产量与钾肥农学效率和利用效率协同提高。综上认为，在本试验条件下，全膜双垄沟播栽培和施钾量为84kg/hm2是半干旱区油葵适宜种植模式，且补灌效果明显。      

Winter wheat canopy interception and its influence factors under sprinkler irrigation

Field studies on winter wheat canopy interception with its relations to leaf area index (LAI), plant height, drop diameter, wind speed, and water application intensity were carried out. Canopy interception was measured using the water wiping method. Results indicate that the maximum value of winter wheat canopy interception was not more than 1.0 mm, much smaller than presented by previous investigators. The total canopy interception for the growing season was 2.4 mm, only 1.3% of the total irrigation amount (194.6 mm), for four sprinkler irrigation events during 2003. Canopy interception increased as leaf area index and plant height increased. A linear regression model was developed to express the relationship of canopy interception with leaf area index and plant height. There was good agreement between the values of canopy interception measured using the water wiping method and estimated using the linear regression model. Results also indicate that canopy interception decreased as drop diameter and wind speed increased. An exponential relationship was found between canopy interception and drop size, and a linear relationship between canopy interception and the square of the wind speed. Water application intensity does not affect canopy interception significantly.     

Attainable yield achieved for plastic film-mulched maize in response to nitrogen deficit

Nitrogen (N) stress limits the yields of maize (Zea mays L.) that have been plastic film-mulched in northwest China. Using the tested Hybrid-Maize simulation model, which was combined with field experiments using four levels of N fertilisers (0, 100, 250 and 400 kg N ha⁻¹), we aimed to understand the variability of the attainable yield in response to N stress under plastic film mulching. We show that the application of N250 or N400 results in 100% simulated potential LAI, which is, thus, close to 100% of the simulated potential of both biomass and grain yield. However, N stress treatments significantly decreased the biomass and grain yields, achieving only 40–50% of the simulated potential (N0 treatment) and 70–80% of the simulated potential (N100 treatment). Growth dynamic measurements showed that N stress significantly decreased the LAI, delaying the source capacity growth (canopies) around the silking stage and resulting in lower final kernel numbers. The lower LAI resulted in decreased dry matter accumulation and allocation during the reproductive stage; this decrease led to a decrease in the kernel growth rate and in the grain filling duration, which resulted in a significantly lower kernel weight. This knowledge could be helpful for the optimisation of N management to close the yield gaps of dryland maize in semi-arid monsoon climate regions.     

全膜双垄沟不同覆膜时期对玉米土壤水分和产量的影响

针对甘肃省旱作农业区年降水量少、季节分布不均匀、玉米生产中春旱严重的问题,采用田间试验的方法研究了全膜双垄沟4种不同覆膜时期对旱地玉米生育时期、土壤水分变化、水分利用效率、产量及经济效益的影响。结果表明:秋覆膜优于早春顶凌覆膜、玉米播前覆膜和晚春播种时覆膜,即早覆膜优于晚覆膜。全膜双垄沟秋覆膜增加了降水利用率和水分利用效率,降水利用率为70.21%,产量为10039.34kg/hm2,比播前覆膜8036.67kg/hm2增产24.92%,水分利用效率36.01kg/hm2·mm,比播前覆膜27.10kg/hm2·mm提高32.88%。全膜双垄沟秋覆膜可明显减少冬春季土壤水分的无效蒸发,增产效果明显,是旱作区进一步挖掘降水潜力和高产田创建的有效途径。     

连作对马铃薯土壤微生物区系和产量的影响

以马铃薯连作1、3和5年的土壤为研究对象,分析了土壤微生物区系和产量的变化。结果表明,随连作年限的增加,土壤中细菌和放线菌数量呈下降趋势,真菌呈上升趋势,轮作与连作1、3和5年间的土壤细菌、真菌和放线菌差异均达极显著水平。与轮作相比,连作1年、3年和5年的土壤纤维素分解菌数量分别下降了21.4%、42.9%和50.0%,固氮菌分别下降了13.0%、39.1%和60.9%,氨化细菌分别下降了2.6%、17.1%和17.1%。随着连作年限的增加,马铃薯产量下降幅度逐年增加,但差异均不显著。     

施氮和豌豆/玉米间作对土壤无机氮时空分布的影响

为探明甘肃河西走廊绿洲灌区豌豆/玉米间作体系土壤无机氮时空分布现状和过量施用氮肥对环境的影响,2011年在田间试验条件下,采用土钻法采集土壤剖面样品,采用Ca Cl2溶液浸提、流动分析仪测定土壤无机氮含量的方法,研究了不同氮水平[0 kg(N)·hm?2、75 kg(N)·hm?2、150 kg(N)·hm?2、300 kg(N)·hm?2、450 kg(N)·hm?2]下豌豆/玉米间作体系土壤无机氮时空分布规律。结果表明:作物整个生育期内,灌漠土无机氮以硝态氮为主,其含量是铵态氮的7.55倍。在玉米整个生育期内,与不施氮相比,75 kg(N)·hm?2、150 kg(N)·hm?2、300 kg(N)·hm?2和450 kg(N)·hm?2处理的土壤硝态氮含量分别增加29.7%、67.5%、88.2%和134.3%。与豌豆收获期相比,在玉米收获时土壤硝态氮含量平均降低44.2%。间作豌豆和间作玉米分别比对应的单作在0~120 cm土层硝态氮含量降低6.1%和5.1%。豌豆/玉米间作体系土壤无机氮累积量在不同施氮量和不同生育时期都是表层(0~20 cm)最高。豌豆收获后,0~60 cm土层土壤无机氮累积量间作豌豆和间作玉米分别比相应单作降低4.9%和1.9%,60~120 cm土层降低10.8%和9.2%;玉米收获后0~60 cm土层平均降低28.2%和9.4%,60~120 cm土层平均降低23.5%和12.5%。土壤无机氮残留量间作豌豆比单作豌豆在0~60 cm土层降低4.9%,60~120 cm降低10.9%。因此,施用氮肥显著增加了土壤无机氮含量和累积量,且主要影响土壤硝态氮。过量的氮肥投入会因作物不能及时全部吸收而被大水漫灌和降雨等途径淋洗到土壤深层,造成氮肥损失和农田环境污染。间作能显著降低土壤无机氮浓度和累积量,特别在作物生长后期对土壤无机氮累积的降低作用更加明显。