降水对青海同德高寒草地牧草产量影响的积分回归分析

利用积分回归的基本原理,并以青海省同德县巴滩高寒草地牧草产量为例,运用积分回归分析气象要素与牧草产量的关系,确定了青海省同德县巴滩高寒草地不同生育时段的降水对牧草产量的影响效应。结果表明,降水对高寒天然草地牧草产量的影响正效应为4月上中旬、5月下旬—7月上旬和8月下旬3个阶段,降水量每增加1mm,牧草产量最大增加138.2,80.1,53.8kg/hm2;负效应为4月下旬—5月中旬和7月中旬—8月中旬2个阶段,降水量每增加1mm,牧草产量相应最多减少23.1,43.7kg/hm2。     

黑液制备的腐植酸液肥和调理剂的棉花田间应用研究

为了给黑液实现资源化利用提供依据,在新疆进行了黑液腐植酸产品的田间试验,设计了3个处理,采用棉花定点定株方法调查其生理指标,并测定其生化指标,研究了它们对棉花的生长、产量和抗旱能力的影响。结果表明,在滴灌中应用腐植酸液肥,与常规固体肥料相比可明显促进棉花在各生育期的生长,能增加蕾、花和铃的数量,并且延长成熟时间,作物不易早衰。同时液肥还可提高棉花的经济性状,能够显著增加籽棉的产量,增产率可达12.3%。在棉花上使用该腐植酸产品后可降低叶片的蒸腾速率,提高叶片的保水能力和CAT活力,从而明显增强棉株的抗旱能力。黑液腐植酸产品对棉花具有良好的促长、增产和抗旱效果。     

巴尔鲁克山天然割草场植物群落分类及群落边界检测

利用DCA分析对巴尔鲁克山天然割草场主要植物群落进行了数量分类。结果表明:该区域割草地可以划分为5个类型,各类型之间在植物多样性丰富,且多样性指数之间差别不大。同时,采用移动分割技术对其群落在空间上的分布进行了划分。群落在0~840 m的空间范围内,具有3个明显的过渡区域,且过渡区域跨度较大,而稳定的植被类型存在区域很窄。在840~1 400 m的空间范围内,距离指数曲线波动更为频繁,经过多窗体计算后,仍然存在多个波峰和波谷,群落结构在空间上处于多变状态,充分说明巴尔鲁克山天然割草地不仅草地植物种类丰富,而且由于环境条件在小尺度范围内变化较大,因而在同一草地类下植物群落分布仍然多种多样。     

建植第1年刈割对黑麦草+白三叶草地杂草空间格局的影响

栽培草地稳定性是近年来草地建植与管理的核心问题之一,其中草地抗杂草入侵是其稳定性的重要表现形式。本研究应用地统计学分析方法,分析了刈割处理下多年生黑麦草(Lolium perenne)+白三叶（Trifolium repens）混播草地杂草生物量空间分布的异质性。结果表明,不同刈割强度下,多年生黑麦草+白三叶混播草地入侵杂草地上生物量空间格局异质化程度及其相关范围变化比较明显。变异函数的基台值(C0+C)在不同刈割强度下的变化表明,在重度刈割条件下,杂草地上生物量空间分布异质性最高(12.530),对照条件下次之(4.751),轻度刈割条件下较低(4.557),中度刈割条件下最低(3.149)。变异函数的相关范围(A0)表明,在重度刈割条件下空间相关范围最大(1 004.1 cm),中度刈割条件下最小(122.1 cm),轻度刈割 (161.9 cm)和对照(219.1 cm)条件下居中。空间变异比分析表明,由空间自相关因素引起的空间异质性占主要部分(50.3%～93.5%)。空间分布格局图(Kriging map)分析进一步显示,不同刈割强度下多年生黑麦草+白三叶混播草地杂草地上生物量格局变化显著。     

调亏灌溉下新型土壤改良剂与氮肥配施对冬小麦水氮利用率的影响

【目的】通过对冬小麦施用一种以农作物秸秆为主要原料研制的新型土壤改良剂,探讨调亏灌溉下该改良剂与氮肥配施对冬小麦产量及土壤水氮利用率的影响。【方法】以冬小麦"西农979"为试验材料,采用田间小区试验,对灌水(灌水量分别为0,1.467m3/hm2)、新型土壤改良剂(施入量分别为0,1 500kg/hm2)和氮肥(纯氮施入量分别为0,160,288kg/hm2)3个因素不同水平进行完全随机组合设计,共12个处理,研究亏灌条件下,新型土壤改良剂和氮肥配施后,成熟期冬小麦产量、土壤水分及氮素利用率的变化情况。【结果】新型土壤改良剂和氮肥单施或配施均能改善成熟期冬小麦土壤水分条件,提高土壤含水量、水分利用率及籽粒产量,且灌水条件下效果更为明显。新型土壤改良剂和氮肥配施不仅明显增加了0～200cm土层土壤硝态氮含量,而且有利于提高植株氮素吸收量。无论灌水与否,1 500kg/hm2新型土壤改良剂和288kg/hm2氮肥配施的增产效果最明显,水分利用效率、植株氮素吸收量均较高。【结论】适度亏灌条件下,新型土壤改良剂与氮肥配施可显著提高作物产量及水氮利用率。     

加乐多土壤调理剂在瓜类蔬菜连作地上的应用效果

为改善瓜类蔬菜种植地连作障碍,探讨了土壤调理剂加乐多的应用效果。试验结果表明,与未施加乐多的处理相比,施用加乐多后,瓠子植株长势旺盛,分枝多,产量增加233．8kg／667m2,增产12％,增收1636．6元／667m2;且提高了土壤pH值,增强了瓠子的耐涝性和抗霜霉病和灰霉病的能力。     

Long-Term Cultivation Effects on Biological C and N Fractions in a Fluvaquentic Haplustolls of Semi-arid Region of the Northern Turkey

Conversion of a native ecosystem can impact the nature and dynamics of organic carbon (C) fractions. The goal of this study was to determine the effects of cultivation and monoculture wheat production on soil organic C and biological C fractions compared to a previously flooded native pasture in northern Turkey. Soil samples were collected from four randomly selected locations of each management system. Some soil chemical [pH, calcium carbonate (CaCO₃), total nitrogen (N), and organic C], physical (sand, clay, and silt), and biological properties [microbial biomass carbon (MBC), mineralizable C, and mineralizable N] were measured. Conversion of pasture to cultivated land slightly increased soil pH, but CaCO₃, total organic C (TOC), and N contents were significantly (P < 0.05) decreased with cultivation. Total organic C and N contents were more than three times less in cultivated soils compared to pasture. Microbial biomass C was significantly decreased (P < 0.05) with long-term cultivation, and the greater seasonal fluctuations were measured at the surface of both ecosystems. The greatest level of potentially mineralizable C was observed in the pasture rather than the cultivated soil, but the proportional distribution of mineralized C to TOC was greater in the cultivated soil. These results suggested that the long-term cultivation (15 years) of previously flooded native ecosystems increased C mineralization and resulted in 72% C loss at the surface soil. Cultivated soils have a greater potential to restore atmospheric carbon dioxide (CO₂) if proper cultivation and management systems are used.     

Application of Near Infrared Reflectance Spectroscopy for the Assessment of Soil Quality in a Long‐Term Pasture

Abstract

The objective of the present study was to assess the ability of near infrared reflectance spectroscopy (NIRS) to analyze chemical soil properties and to evaluate the effects of different phosphorus (P) and potassium (K) fertilization rates on soil quality in different layers of a long‐term pasture. The NIRS calibrations were developed for humus, total Kjeldahl nitrogen (N_Kjeldahl), and several humic substances (HA1, “mobile” humic acids fraction; ΣHA, sum of humic acids; FA1, “mobile” fulvic acids; ΣFA, sum of fulvic acids, etc.) using soil samples of rather heterogeneous origin, collected during 1999–2003. Different spectral preprocessing and the modified partial least squares (MPLS) regression method were explored to enhance the relation between the spectra and measured soil properties. The equations were employed for the quality prediction of a sod gleyic light loam (Cambisol) in five PK fertilization treatments. The soil was sampled in 2000 and 2003 in three field replicates at depths of 0–10, 10–20, 20–30, and 30–50 cm, n=60 samples yr^?1. The best coefficients of correlation, R², between the reference and NIRS‐predicted data were as follows: for N_Kjeldahl, 0.965; humus, 0.938; HA1, 0.903; HA2, 0.905; HA3, 0.924; ΣHA, 0.904; and FA1, 0.911; and ΣFA, 0.885. Our findings suggest that it is feasible to use NIRS for the assessment of the effects of the inorganic PK fertilizer on the soil quality in different depths of a long‐term pasture.     

Changes in Soil Properties under Two Different Management Systems in the Western Amazon

Upland soils in the Amazon basin are often highly weathered and therefore possess low plant-available nutrient contents. Soil fertility is principally maintained by geochemical, biochemical, and biogeochemical processes. Within these processes, the soil microbial biomass is responsible for many of the cycles and transformations of nutrients in soils. The aim of this work was to evaluate the changes in soil fertility, in the form of nitrogen (N) and microbial activity, as indicators of the dynamic of carbon (C) with two extractants [irradiation extraction (IE) and IRGA methods], N, and phosphorus (P) in an upland soil area containing a dystrophic Yellow Latosol (Xanthic Ferralsol) in the western Amazon (Brazil) with succession of two plant covers (citrus or pasture) and management. The study was carried out in two chronosequences: primary forest followed by citrus plantations and primary forest followed by pasture. The results showed that pasture has greater capacity to accumulate organic C and total N than either primary forest or citrus plantation. Removing forest to introduce pasture or citrus plantations influences the soil fertility and microbial biomass of C, N, and P in the soil. Under the edaphoclimatic conditions, the irradiation extraction and IRGA methods all proved efficient in determining the soil microbial C activity. In addition, regardless of the depth of soil, the predominant N form is ammonium (NH₄ ⁺).     

A comparative study on chemical characteristics of tropical soils from volcanic material under forest and agriculture

Abstract

An investigation was conducted to compare differences in chemical characteristics of Costa Rica soils under continuous cultivation and under forest vegetation. Inceptisols from young volcanic material under forest, sugar cane, coffee and pasture, respectively, were sampled in the San Carlos region of Costa Rica, and analysed for pH, organic matter, N, Ca, Mg, K, Na, Al, Fe, Zn and Mn contents. Indications were obtained that continuous cropping for 1 to 22 years with sugar cane resulted in a decrease in Ca and Mg content and an increase in acid extractable Al concentrations, compared to amounts found in forest soils. In soils under coffee the only significant changes were a reduction in soil organic matter, N and Al contents. Exchangeable bases decreased slightly during the first two years, but in fields 15 years under coffee, the content of exchangeable bases was affected slightly, except for a relatively marked decrease in amounts of Mg. Conversion into pasture maintained soil fertility at a level comparable to that found in the forest soil ecosystem. It was concluded that differences in vegetational ecosystems caused soil chemical changes, but deforestation in the tropics did not necessarily result in rapid soil degradation processes. The magnitude of the data showed that the soil in the San Carlos region of Costa Rica had been cultivated for at least 10 to 20 years without producing evidence of excessive deterioration.