(土娄)土区不同蔬菜对钾肥的肥效反应

在陕西省关中土娄土区布置线辣椒、甘蓝、白菜、芹菜钾肥大田试验,研究不同蔬菜对钾肥的肥效反应。结果表明,增施钾肥可使蔬菜硝态氮含量降低11.8%～116.0%,维生素C含量增加0.4～147.4mg/kg;产量增加9.3%～33.8%;明显促进营养生长和生殖生长;400cm深土壤剖面硝态氮累积量减少22.7～48.0kg/hm2,尤其在80～220cm剖面减少最为明显。     

甘肃河西地区盐碱地野生药用植物资源

甘肃河西地区盐碱地野生药用植物资源丰富,主要有50种,隶属于21科40属。针对当地农业生产状况,应合理开发利用盐生药用植物资源。     

西安白鹿塬约85OO年来土壤侵蚀研究

本文根据作者的观察和测量，对西安市白鹿塬塬区的土壤侵蚀状况进行了研究。研究表明，白鹿塬塬区确定土壤侵蚀的主要依据是土层厚度的变化，并非侵蚀面。塬区侵蚀是塬边侵蚀较强，向塬里侵蚀逐渐减弱。塬面上高地侵蚀弱，低地侵蚀强，暂时性线状流水长期汇集而成的冲沟对黄土塬区土壤的侵蚀更加强烈。气候对土壤侵蚀也有影响，冷干和温湿气候均会产生土壤侵蚀，冷干期侵蚀量比温湿期大，前者侵蚀厚度比后者大7倍多。     

北京春季沙尘天气特征和预报

根据北京地区资料分析了沙尘的年代变化、月变化,春季是沙尘天气的高发期并以浮尘和扬沙为主。造成沙尘天气的冷空气主要有三条路径,它与蒙古气旋、冷锋、高空急流等大尺度天气系统紧密相连。     

新疆盐碱地种植耐盐小麦土壤盐分的变化

新疆干旱区有大量盐碱地 ,很大程度上限制农业的可持续发展。盐碱的利用改良和水资源的高效利用的研究 ,面临巨大的挑战。盐碱地上种植耐盐小麦既有生产效益 ,又有改良土壤盐渍化作用。在传统灌溉管理下 ,当土壤原始盐分 2 .0 %时 ,在壤质土壤上种植耐盐小麦 1— 2年 0— 40cm土层盐分可降到 0 .8%。在粘壤土、壤土土质的土壤中 ,种植耐盐小麦 5年时 ,0— 1 0 0cm土层盐分可降到 0 .5 % ;种植 7年后 ,0— 1 0 0cm土层盐分降到 0 .2 %左右 ,且在以后种植条件下 ,土壤盐分趋于平衡状态 ,变化很小。种植耐盐小麦引起的盐分变化 ,灌溉水为主要作用 ,以至经多年种植 ,土壤表现为脱盐碱化现象。     

不同覆盖方式对旱地玉米田土壤环境及玉米产量的影响

分析普通地膜覆盖、小麦秸秆覆盖及露地栽培3种不同处理对旱地玉米田土壤环 境、玉米产量构成因素的影响,结果表明:覆盖栽培能改善土壤环境,降低土壤容重,提高土壤 水分利用率,调节土温、湿度,协调水热资源利用的同步性;秸秆覆盖能增加土壤养分含量,特 别是速效钾含量;在玉米生长后期,提高叶面积指数,延长叶片功能,提高玉米的光合能力从而 防止玉米早衰,增加穗重,提高玉米产量。     

Effect of recent cropping history and herbicide use on the degradation rates of isoproturon in soils

Five soil samples were taken from each of five fields with different crop management histories. Three of the fields were in an arable rotation, the fourth field was temporary grassland, and the final field was under permanent grass. Of the three arable fields, two had been cropped with winter wheat in three of the preceding 6 years, and the third had last been cropped with winter wheat once only, 6 years previously. With one exception, the winter wheat had been sprayed with the herbicide isoproturon. The rate of isoproturon degradation in laboratory incubations was strongly related to the previous management practices. In the five soils from the field that had been treated most regularly with isoproturon in recent years, <2.5% of the initial dose remained after 14 days, indicating considerable enhancement of degradation. In the soils from the field with two applications of the herbicide in the past 6 years, residues after 27 days varied from 5% to 37% of the amount applied. In soils from the other three sites, residue levels were less variable, and were inversely related to microbial biomass. In studies with selected soils from the field that had received three applications of isoproturon in the previous 6 years, kinetics of degradation were not first‐order but were indicative of microbial adaptation, and the average time to 50% loss of the herbicide (DT₅₀) was 7.5 days. In selected soils from the field that had received just one application of isoproturon, degradation followed first‐order kinetics, indicative of cometabolism. Pre‐incubation of isoproturon in soil from the five fields led to significant enhancement of degradation only in the samples from the two fields that had a recent history of isoproturon application.     

华北农牧交错带退化草地土壤种子库动态变化

对华北农牧交错带不同退化演替阶段土壤种子库的数量和物种组成及与地上植被的关系进行了初步的研究,结果表明:农牧交错带草地在刈割和放牧等干扰下,发生逆行演替,土壤种子库中植物种类及种子数量呈递减的趋势,轻度退化类型土壤种子库物种组成最高,有23种植物,种子数量最多,有4 303粒,禾本科所占比例较大,为32.3%;而极度退化草地物种组成最低,有14种植物,种子数量仅有1 156粒,禾本科只占8.4%.草地逆行演替过程中植被与土壤种子库在物种组成上存在一定差别,中度退化阶段差别最大,有18种植物未在种子库中出现,极度退化阶段差别最小,有2种未在种子库中出现.     

植物化感作用影响因素的再认识

土壤养分、酶、微生物、本底特性,根茬还田、水分、植物根系、种植体系和种植模式与化感作用的互作关系,表明这些因子可通过对土壤养分有效性、微生物种群结构、土壤酶活性和化感物质浓度的影响而对化感作用产生直接或间接影响,这些可为通过化感作用途径构建高效农田生态系统提供新的思路.     

几种牧草对河西走廊盐渍化土壤改土培肥的效应研究

在河西走廊盐渍化土地上种植老芒麦、扁穗冰草、碱茅和紫花苜蓿4种优质牧草,对盐渍化程度均有一定的改良效果.其中碱茅对盐渍化土壤的改土培肥效果最好,建植3年后的碱茅,与对照比较,0～20 cm土层中自然含水量增加125.99 g/kg,总孔度增加16.14%,容重降低0.27 g/cm3,pH值由8.43降到8.10,全盐含量降低52.90 g/kg,脱盐率达到76.12%,有机质增加3.67 g/kg,碱解氮含量增加18.63 mg/kg,速效磷和钾亦随之增加.