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101.
以大量原始史料为基础,对中国共产党在特定形势下发起的农业生产互助运动进行了研究,考察了这一时期革命根据地农业生产互助组织的组织特征、运行机制和绩效。 相似文献
102.
《Communications in Soil Science and Plant Analysis》2012,43(4):299-310
Abstract Extractable li with ammonium acetate was determined by flamephotometry, in normal soils, alkaline soils and saline soils in the Province of La Pampa (Argentina). The soils were originated from differents parent material, with various rainfalls (arid to subhumid climate) and management. The higher contents were found in saline soils. In the other soils the extractable lithium content depends on the parent material, but not on rainfall. Different patterns of vertical and horizontal distribution of extractable lithium were found. The origin of extractable lithium is here discussed. 相似文献
103.
《Communications in Soil Science and Plant Analysis》2012,43(7):615-627
Abstract Soil pH's were evaluated at three time intervals following land clearing at two locations in the Matanuska Valley. Seasonal fluctuations of pH values over a seven‐year period as determined in water (pHw,) and 0.01 M CaCl2 (pHs) were additionally evaluated at these locations. A statistical rise in soil pH occurred at both locations with clearing and subsequent cultivation. Soil reaction differences related to season and year were not consistent and were not related to a definite pattern. No relationship between monthly or seasonal precipitation and the soil reaction was found. The correlation coefficient between pHw and pHs was highly significant. Work of other investigators is discussed in the interpretation of the data collected. 相似文献
104.
《Communications in Soil Science and Plant Analysis》2012,43(17-18):2343-2358
Abstract Magnesium (Mg) is an essential macronutrient element for all living organisms, but literature reports of Mg deficiency in agriculture and forestry appear regularly. In many tropical areas, Mg is added to soils by using dolomitic limestone and as minor additions through impurities in some fertilizers. Minimal information is available on the Mg status of Fiji soils, and deficiencies have been observed in some crops. This study investigated the Mg status of a range of Fiji soils and found that major agricultural soils of Fiji contain variable amounts of Mg, both in the total concentrations and in the different forms of the element present. The variations can be related to the soil parent materials, degree of weathering, clay content, and mineralogy. Low plant‐available Mg concentrations are present in many of the highly weathered soils with limited reserves present. Development of intensive agriculture should consider Mg when developing fertilizer programs. 相似文献
105.
《Communications in Soil Science and Plant Analysis》2012,43(10):995-1007
Abstract Negative yield responses are common when highly leached soils are limed to neutrality. A number of explanations have been proposed, but very few have been experimentally verified or are entirely acceptable. In this paper the problem is re‐examined and a new possible causal mechanism is proposed. Data assembled from the literature are used to demonstrate that a consistently observed reduction in Mg uptake by plants when soils are limed to neutrality is often accompanied by a generally ignored reduction in exchangeable soil Mg. Using data for soils of North American and African origin, it is demonstrated that when the soils were limed with pure Ca sources, the level of exchangeable soil Mg was reduced between 36 and 93%. Furthermore, after treatment with a Mg containing liming material, initial increases in the level of exchangeable Mg were followed by similarly large decreases when the soil pH approaches neutrality. The applicability of known Mg fixation mechanisms is briefly discussed and the suggestion is made that Mg fixation may offer an acceptable explanation for some of the yield depressions observed on liming to neutrality. Research is currently in progress to gather sufficient data to answer the many questions raised. 相似文献
106.
107.
随着我国水资源供需矛盾的日益尖锐和水资源环境的日趋恶化,节水已成为我国解决水问题的有效途径之一。本文介绍几种节水技术,并分析利弊,反映柴达木盆地农业节水新观点、新思路,为农业节水更好的发展提供参考。 相似文献
108.
甘肃省干旱半干旱地区降水的研究 总被引:1,自引:1,他引:1
本文通过对甘肃省降水资料的具体分析,指出了在干旱、半干旱地区降水的主要特征,如暴雨的特殊性、固体降水与海拔关系、降水量与海拔关系、降水量与作物产量关系等,并对如何提高降水利用率,发展农业生产等问题进行了探讨。 相似文献
109.
110.
Adsorption-desorption of the herbicide flufenacet (FOE 5043) has been studied in five soils from different locations in India (Delhi, Ranchi, Nagpur, Kerala and Assam) varying in their physicochemical properties. The organic matter (OM) content varied from 0.072 to 0.864%, clay content from 2.5 to 43.7% and pH from 4.45 to 8.35. The adsorption studies were carried out using a batch equilibration technique. Ten grams of soil were equilibrated with 20 ml of aqueous 0.01 M CaCl2 solution containing different concentrations (0-30 mg litre-1) of flufenacet. After equilibration, an aliquot of supernatant was taken out for analysis. During desorption, the amount withdrawn for analysis was replenished with fresh 0.01 M CaCl2 solution and further equilibrated. Desorption studies were carried out with the 30 mg litre-1 concentration of flufenacet only. The adsorption studies revealed that there was moderate to high adsorption of flufenacet considering the comparatively low organic carbon content in the five test soils. Average Kd values ranged from 0.77 to 4.52 and Freundlich KF values from 0.76 to 4.39. The highest adsorption was observed in Kerala soil (OM 0.786%; clay 25%; pH 4.45) followed by Ranchi, Nagpur and Delhi soils, and the lowest in Assam soil (OM 0.553%; clay 2.5%; pH 6.87). The trend in adsorption could be attributed to the chemical nature of flufenacet and the physicochemical properties of the soil such as pH, OM and clay contents. OM and clay contents were positively correlated whereas pH was negatively correlated. Soils having low pH, high OM and high clay contents showed higher adsorption. Desorption studies revealed that there was a hysteresis effect in all the soils. Hysteresis coefficient values (ratio of n(ad) and n(des)) varied from 0.09 to 0.45. The study implies that, because of its moderate to high adsorption, flufenacet is likely to persist in soil for some time. However, the possibility of its movement by leaching or surface run off is less. 相似文献