前茬冬季覆盖作物对稻田土壤的生物特征影响

通过对我国南方稻区不同冬季覆盖作物前茬对稻田主要微生物类群数量和主要土壤化学性状的变化进行研究,结果表明：冬季紫云英和黑麦草覆盖在翌年水稻田翻耕前土壤好气细菌、真菌、放线菌数量均比冬闲田高,其中好气性细菌数量差异最显著,分别是冬闲田的94.29%和25.71%;在水稻整个生长过程土壤细菌、真菌和放线菌均呈现移栽后前期迅速增加,然后随着水稻的生长发育逐渐下降,到早稻成熟期有渐渐回升,晚稻收获时又迅速下降的趋势,并且不同时期微生物数量冬季紫云英和黑麦草区均比冬闲田要高。土壤微生物活度在水稻生长过程呈增加的趋势,前茬冬季覆盖作物区明显高于冬闲田。另外土壤微生物活度与土壤有机碳含量存在显著的相关性（r^2=0.887,P〈0.05）。冬季种植覆盖作物对稻田土壤微生物有很强的改善作用,促进了土壤养分利用。     

有机无机肥配施对小麦吸收氮磷及土壤肥力的影响

￣（１５）Ｎ示踪试验表明，有机无机肥配施促进了有机叉的矿化和小麦对有机氮的吸收利用，基施氮肥主要用于营养器官的形成，返青追肥主要用于生殖器官的形成。有机无机氮肥配施提高了总氮生产效率。配施处理小麦对磷素的吸收总量稍高于单施无机氮肥处理，磷素在籽粒中的分配率稍低于单施无机氮肥处理是导致磷素生产效率下降的重要因素。有机无机肥配施提高小麦产量的同时也培肥了地力，是小麦高产稳产的重主措施之一     

河南省主要耕地土壤肥力监测报告

根据1998～2004年连续7年对河南省45个土壤肥力监测点的监测结果，以及对645个土壤样品12个项目的分析化验，已初步掌握了河南省近年主要耕地类型的肥力变化状况。结果表明，与第二次土壤普查（1986年）时相比，高、中地力为主的耕地土壤各养分含量除速效钾下降明显外，有机质、全氮、碱解氮、速效磷以及有效微量元素等都有不同程度的提高，尤以速效磷提高最快。土壤速效钾7年平均值119．96mg/kg，比第二次土壤普查时下降了18．94mg/kg，平均每年以1．05mg/kg的速度下降，但近年来下降趋势变缓；养分平衡中氮素（N）平均盈余39．5kg／hm^2，磷素（P2O5）盈余30．9kg／hm^2，钾素（K20）亏缺150．0kg／hm^2；全省施肥水平较高，每公顷总施肥量折纯养分647．96k，但有机无机比仍不合理，化肥氮、磷、钾投入比例1：0．42：0．17，氮肥充足，部分地区用量偏高，磷肥基本合理，钾肥不足；主要农作物小麦产量略有上升，其它主要秋收作物产量基本稳定。     

长期免耕水稻田土壤的生物特征研究

对经过 10年半旱式免耕定位试验的水稻土主要微生物类群数量和微生物生物量的变化进行对比研究 ,结果表明 :实行半旱式厢作及垄作免耕法能够迅速地提高土壤有机质、全氮、全磷和速效氮、磷的水平 ;微生物数量和微生物生物量变化一般存在季节性规律 :春季高 ,夏季至夏末降低 ;各处理土体上层和下层 (0～ 7.5 cm,7.5～15 cm)的基本肥力特征及微生物特征无明显区别 ;免耕处理土壤 ,其微生物的季节性变幅较小 ,垄上或厢上土壤微生物生物量甚至表现反季节性 ,整个生长季节内稳中有升 ,有利于土壤有机物质的转化和土壤肥力的发挥     

广西红壤果园土壤肥力演化与评价

本文着重探讨广西红壤果园土壤肥力在不同种植年限的演化特征,并利用数理统计软件—SPSS对果园土壤肥力进行综合评价。结果表明,广西红壤果园土壤肥力综合指标值(IFI)在0.17～0.25之间,果园土壤肥力属中下水平。不同年限果园IFI的变化趋势为"N"形走势,即新开果园在10年内IFI略有上升,10年后下降,而在30年以后果园土壤IFI又有增加。造成这种走势的原因,主要是由于受广西高温多雨的气候、果园环境和施肥管理等方面共同影响的结果。在近15年开垦种植的果园中,由于水土流失严重,果园土壤砂化,11～15年树龄果园的砂粒含量比0～5年树龄果园增加近23个百分点,而团聚体(>1mm)和有效阳离子代换量(ECEC)却分别减少24个百分点和3.0cmol/kg,果园土壤环境恶化。防止新开果园水土流失,改善新开果园土壤环境,为广西水果生产的当务之急。     

Soil nitrogen distribution and deposition on shortgrass prairie adjacent to a beef cattle feedyard

Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased with distance downwind from the feedyard from 1.6 ± 0.2 g kg⁻¹ at 75 m to 1.2 ± 0.05 g kg⁻¹ at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N concentration decreased linearly (P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg⁻¹ within 75 m from the feedyard to 5.8 ± 1.5 mg kg⁻¹ at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha⁻¹ year⁻¹ over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that returned to typical and expected levels for undisturbed shortgrass prairie.

黄土高原旱地不同施肥对土壤肥力与产量的影响

Long-term fertility experiments have become an important tool for investigating the sustainability of cropping systems. Therefore, a long-term (18-year) fertilization experiment was conducted in Changwu County, Shaanxi Province, China, to ascertain the effect of the long-term application of chemical fertilizers and manure on wheat yield and soil fertility in the Loess Plateau, so as to provide a scientific basis for sustainable land management. The experiment consisted of nine fertilizer treatments with three replicates arranged in a completely randomized design: 1) CK (no fertilizer); 2) N (N 120 kg ha-1); 3) P (P 26.2 kg ha-1); 4) NP (N 120, P 26.2 kg ha-1-2); 5) M (manure 75 t ha-1); 6) NM (N 120 kg ha-1, manure 75 t ha-1); 7) PM (P 26.2 kg ha-1, manure 75 t ha-1); 8) NPM (N 120 , P 26.2 kg ha-1, manure 75 t ha-1); and 9) fallow (no fertilizer, no crop). N fertilizer was applied in the form of urea and P was applied as calcium super phosphate. The results showed that precipitation had a large effect on the response of wheat yield to fertilization. Manure (M), NP, PM, NM, and NPM treatments significantly increased (P < 0.05) average yield. In the NP, PM, NM and NPM treatments, the percentage increases in yield due to fertilization were highest in normal years, and lowest in the drought years. Long-term P application enhanced soil available P markedly, and manure applications contributed more to soil fertility than chemical fertilizers alone. Chemical fertilizers applied together with manure distinctly improved soil fertility. The results also showed that the soil nutrient concentration changed mainly in the 0--60 cm layers and fertilization and planting only slightly affected soil nutrients below the 100 cm layers.     

Changes in the properties of a Mexican Fluvisol following 30 years of sugarcane cultivation

A study to evaluate the changes in the fertility of Fluvisols under continuous cultivation of sugarcane was conducted in the vicinity of the Santa Rosalía sugar refinery. About 4000 ha of Fluvisols have been under sugarcane cultivation for more than 30 years. Three representative plots under monoculture for 5, 10, 20 and 30 years, were selected under on-farm conditions. Several samples were obtained from crop row and inter-row zones, at 0–30 cm soil depth, and composited into four samples for each plot. Soil samples were analyzed for pH, organic matter, total organic C, total nitrogen, available phosphorus, exchangeable potassium, calcium and magnesium, cation exchange capacity, texture and bulk density. There were significant changes in the soil chemical properties due to 30 years of monoculture, except for OM, exchangeable K, Ca, Mg and CEC. Total soil organic C, total N and P declined by 17, 21 and 37%, respectively, by 30 years of monoculture of sugarcane. These losses mainly occurred during the first 20 years of cultivation. However, the adverse effect of decline in soil fertility was not reflected in the sugarcane yields. The 67% increase in yields observed between 5 and 30 years of monoculture may be attributed to the adoption of recommended cultural practices and to farmer's experience. Soil physical properties were not affected by the intensive sugarcane cultivation. A complete adoption of recommended practices by SR among farmers and a revision of the N and P fertilization rate are necessary to maintain the fertility of sugarcane soils.     

Evaluation of soil fertility under different Cupressus chengiana forests using multivariate approach

The distribution and growing conditions of Cupressus chengiana forests along with the physical and chemical properties of soils in Northwest Sichuan were studied in 2002 to investigate the conditions and characteristics of soil fertility of C. chengiana and to compare and investigate differences of soil fertility for six C. chengiana populations and their relationships with vegetation, climate and disturbance. The results of the study at 0-20 cm soil depth showed that 1） significant differences （P〈0.05） existed among populations for soil bulk density, soil total porosity, capillary porosity, maximum water-holding capacity, capillary water-holding capacity and topsoil natural water content; 2） chemical characteristics of soil organic matter, total N, total P, alkali-hydrolyzable N, available P, available K and cation exchange capacity were significantly different among the populations; and 3） based on the significant effect of soil fertility factors on forest growth, soil physical and chemical characteristics could be selected as an integrated fertility index （IFI） for evaluation of different C. chengiana populations. Principal component and cluster analyses showed significant differences probably due to the difference of vegetation conditions, management measurements, human-induced disturbances and environmental factors. In order to protect the soil ecological functions in fragile ecological regions, C. chengiana could be used in programs enclosing the hill for natural afforestation, natural forest protection programs, and programs replacing agriculture with afforestation measures.     

Dry farming with soils under natural tephra cover in Lanzarote, Spain

Abstract. The volcanic island of Lanzarote (Canary Islands, Spain) is one of the most arid parts of the European Union. During the eruptions of 1730–36, a third of the island was covered with lava and pyroclastic material. In areas under basaltic tephra, an agrosystem has been developed that allows a form of dry farming that has become a key component of the local economy. This article illustrates the effectiveness of the layer of natural tephra mulch in conserving soil and water.