Long-term fertilization effects on active ammonia oxidizers in an acidic upland soil in China

The effects of long-term fertilization of acidic soils on ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities and its ecological implications remain poorly understood. We chose an acidic upland soil site under long-term (27-year) fertilization to investigate ammonia oxidizer communities under four different regimes: mineral N fertilizer (N), mineral NPK fertilizer (NPK), organic manure (OM) and an unfertilized control (CK). Soil net nitrification rates were significantly higher in OM soils than in CK, N or NPK soils. Quantitative analysis of the distribution of amoA genes by DNA-based stable isotope probing revealed that AOA dominate in CK, N and NPK soils, while AOB dominate in OM soils. Denaturing gradient gel electrophoresis and clone library analyses of amoA genes revealed that Group 1.1a-associated AOA (also referred to as Nitrosotalea) were the most dominant active AOA population (>92%), while Nitrosospira Cluster 3 and Cluster 9 were predominant among active AOB communities. The functional diversity of active ammonia oxidizers in acidic soils is affected by long-term fertilization practices, and the responses of active ammonia oxidizers to mineral fertilizer and organic manure are clearly different. Our results provide strong evidence that AOA are more highly adapted to growth at low pH and low substrate availability than AOB, and they suggest that the niche differentiation and metabolic diversity of ammonia oxidizers in acidic soils are more complex than previously thought.     

优化施肥对春小麦产量、氮素利用及氮平衡的影响

2009 ～ 2010年,在宁夏引黄灌区分别以宁春11号和宁春16号小麦为供试作物,利用田间试验研究了优化施肥(OPT)和习惯施肥(CON)对春小麦产量、氮素吸收利用和土壤硝态氮累积的影响,表观评估了土壤—小麦体系氮素平衡.结果表明,相对于CK处理,OPT和CON都显著提高春小麦籽粒产量地上部生物量,并促进籽粒N和地上...     

秃杉人工林施肥效应试验初报

采用不同肥料种类和施肥剂量对秃杉人工林进行施肥对比试验。观测胸径、树高和蓄积生长量,分析不同肥料种类和施肥剂量对秃杉人工幼龄林高、粗和蓄积生长量的效应。试验结果表明,合理的施肥措施对秃杉人工林生长有明显促进作用,与对照相比,年高生长增加34%,粗生长增加26%,蓄积生长增加35%。     

史密斯桉造林密度与施肥模式研究

针对史密斯桉造林密度与施肥模式进行了研究，对试验地设置3种造林密度作主区，4种施肥模式作副区。对17个月生史密斯桉的试验调查进行分析，结果表明：造林密度对树高生长量的影响差异不显著，而对胸径影响差异显著，适宜密度为2000株·hm^-2。施肥对史密斯桉幼树树高、胸径生长的影响极显著，不同的施肥模式对史密斯桉幼林生长的效果是：桉树专用肥>复混肥+微肥>复混肥+磷肥+微肥>复混肥+磷肥。     

应用~(15)N示踪探究楸树无性系对氮素的吸收和分配

为探讨楸树无性系对氮素的吸收、分配及利用特性,以2年生楸树无性系015-1、1-3、7080、1-4和004-1组培苗为试验材料,应用15N示踪技术对楸树无性系进行施肥试验。结果表明,5个楸树无性系氮肥的吸收率、利用率及分配率具有较强的一致性,氮肥利用率介于27.14%~31.24%之间。楸树无性系根和叶的肥料氮比例(Ndff)明显大于茎,楸树无性系根和叶对氮肥的竞争力较强,茎对氮肥的竞争力最弱。015-1茎部氮素分配率及无性系7080根部氮素分配率明显高于其他4个无性系;氮素分配率在各个器官中差异显著,叶片氮素的分配率最高,总体趋势为叶根茎。本研究结果为楸树氮肥的合理施用提供了理论依据。     

浅析科学施肥

肥料对农作物增长、稳产、高产非常重要,就科学施肥的意义以及施肥中常见的问题做以分析,提出科学施用化肥方法,提高肥料利用率。     

农户过量施用化肥行为的影响因素分析——以新疆棉花种植户为例

过度施用化肥带来的负外部性使棉区土壤面临着棉花增产和保护生态环境的双重挑战。本文在棉花生产的决策主体农户尺度上,利用对新疆重点植棉地区实地问卷调查所得数据,定量化研究了新疆棉农过度施用化肥程度,并通过经济计量模型分析了导致农户过量施用化肥的主要因素。研究结果表明,新疆棉花种植农户的化肥施用量(折纯量)平均达到610.20 kg·hm~(-2),过量施用率占到实际施用量的59.6%。导致农户过量施用化肥的主要因素是缺乏科学施肥培训和避免收入损失的盲目性。研究结果在农户行为学方面做了有益的科学探讨,并为科学引导农户合理施肥提供了科学依据。     

Short time effects of biological and inter-row subsoiling on yield of potatoes grown on a loamy sand,and on soil penetration resistance,root growth and nitrogen uptake

Soil compaction, especially subsoil compaction, in agricultural fields has increased due to widespread use of heavy machines and intensification of vehicular traffic. Subsoil compaction changes the relative distribution of roots between soil layers and may restrict root development to the upper part of the soil profile, limiting water and mineral availability. This study investigated the direct effects of inter-row subsoiling, biological subsoiling and a combination of these two methods on soil penetration resistance, root length density, nitrogen uptake and yield. In field experiments with potatoes in 2013 and 2014, inter-row subsoiling (subsoiler) and biological subsoiling (preceding crops) were studied as two potential methods to reduce soil penetration resistance. Inter-row subsoiling was carried out post planting and the preceding crops were established one year, or in one case two years, prior to planting. Soil resistance was determined with a penetrometer three weeks after the potatoes were planted and root length density was measured after soil core sampling 2 months after emergence. Nitrogen uptake was determined in haulm (at haulm killing) and tubers (at harvest). Inter-row subsoiling had the greatest effect on soil penetration resistance, whereas biological subsoiling showed no effects. Root length density (RDL) in the combined treatment was higher than in the separate inter-row and biological subsoiling treatments and the control, whereas for the separate inter-row and biological subsoiling treatments, RLD was higher than in the control. Nitrogen uptake increased with inter-row subsoiling and was significantly higher than in the biological subsoiling and control treatments. However, in these experiments with a good supply of nutrients and water, no yield differences between any treatments were observed.     

Radiation interception and radiation use efficiency of potato affected by different N fertigation and irrigation regimes

Three years of field experiments were carried out to explore the response of potato dry matter production, accumulated intercepted photosynthetic active radiation (Aipar) and radiation use efficiency (RUE) to five N levels providing 0, 60, 100, 140 and 180 kg N ha⁻¹ and three drip irrigation strategies, which were full, deficit and none irrigation. Results showed that, irrespective of years, dry matter production and Aipar were increased by prolonged N fertigation, even though N fertigation was carried out from middle to late growing season. The highest total and tuber dry matter and accumulated radiation interception in all three years were obtained when potatoes were provided with 180 kg N ha⁻¹. RUE on the other hand was not affected by N regime. Thus, increases in total dry matter production with increasing N levels were essentially caused by higher Aipar. The strongest response to N fertilization occurred when most N was applied early in the growing season and the latest N fertilization should be applied no later than 41–50 days after emergence. Deficit irrigation, which received ca.70% of irrigation applied to full irrigation, did not reduce radiation interception and radiation use efficiency.     

Contribution of green manure legumes to nitrogen dynamics in traditional winter wheat cropping system in the Loess Plateau of China

Excessive application of N fertilizer in pursuit of higher yields is common due to poor soil fertility and low crop productivity. However, this practice causes serious soil depletion and N loss in the traditional wheat cropping system in the Loess Plateau of China. Growing summer legumes as the green manure (GM) crop is a viable solution because of its unique ability to fix atmospheric N₂. Actually, little is known about the contribution of GM N to grain and N utilization in the subsequent crop. Therefore, we conducted a four-year field experiment with four winter wheat-based rotations (summer fallow-wheat, Huai bean–wheat, soybean–wheat, and mung bean–wheat) and four nitrogen fertilizer rates applied to wheat (0, 108, 135, and 162 kg N/ha) to investigate the fate of GM nitrogen via decomposition, utilization by wheat, and contribution to grain production and nitrogen economy through GM legumes. Here we showed that GM legumes accumulated 53–76 kg N/ha per year. After decomposing for approximately one year, more than 32 kg N/ha was released from GM legumes. The amount of nitrogen released via GM decomposition that was subsequently utilized by wheat was 7–27 kg N/ha. Incorporation of GM legumes effectively replaced 13–48% (average 31%) of the applied mineral nitrogen fertilizer. Additionally, the GM approach during the fallow period reduced the risk of nitrate-N leaching to depths of 0–100 cm and 100–200 cm by 4.8 and 19.6 kg N/ha, respectively. The soil nitrogen pool was effectively improved by incorporation of GM legumes at the times of wheat sowing. Cultivation of leguminous GM during summer is a better option than bare fallow to maintain the soil nitrogen pool, and decrease the rates required for N fertilization not only in the Loess Plateau of China but also in other similar dryland regions worldwide.