Tillage methods and soil and water conservation in eastern Africa

This paper reviews some research studies on tillage methods influencing soil and moisture conservation in the eastern African countries of Kenya, Tanzania, Malawi and Ethiopia during the past four decades. Most of these studies were conducted in marginal rainfall (semi arid) areas and on shallow soils of various textures (sandy clay loam, sandy clay, clay and loam). The studies were meant to establish the effects of tillage and residue management practices on physico-chemical soil properties (i.e. structure, bulk density, soil moisture and organic matter contents), runoff and infiltration.

This review emphasizes the importance of appropriate tillage and residue management methods (contour bunds and terraces, minimum tillage, tied ridging, mulching and conventional tillage) in providing soil conditions favourable for soil moisture conservation and subsequent crop performance and yield on smallholder farms.     

Tillage methods and soil and water conservation in Australia

Tillage in Australia has evolved from ‘imported’ European practices to tillage systems more in tune with ‘older’ fragile soils and more severe climatic conditions. Cereal yields are commonly limited by water supply and the native fertility of many soils is poor. Crop/pasture rotations involving pasture legumes have been the mainstay of cereal production in the winter rainfall areas while production in much of the summer rainfall area has relied more on exploiting native fertility. Soil erosion and structural decline are still considered major issues facing long-term production. The general trend in tillage methods is for less tillage and greater retention of crop residues for soil and water conservation.

Tillage experiments have shown that management strategies involving retention of crop residues (stubble), reduced tillage and crop rotation can reduce erosion and improve yield. Results from experimentation are highly variable, both in magnitude and direction of responses to tillage treatments. Much of this variation is due to variation in seasonal conditions. Simulation models are being used to examine management options and to design experiments based on a knowledge of climate variability and physical and biological processes.     

Tillage methods and soil and water conservation methods in the Caribbean

This review describes the tillage methods and soil conservation methods currently utilized in the Commonwealth Caribbean on a range of slopes. A high percentage of the land has slopes which exceed 20° minimum. In these circumstances, tillage is carried out with hand tools and frequently combined with conservation contour drains or/and barriers of cut vegetation laid across the contour. Many farmers form ridges and furrows on the contour with hand tools and a significant number do not use any conservation measures. Tillage, on flat or gently sloping land, is done largely by tractor drawn implements and the tillage method is mainly determined by the crop to be grown and the soil type. The tillage methods used for the cultivation of sugar cane, rice, banana, vegetables and other small row crops are described. The agronomic, cultural and engineering practices used to conserve the soil against water erosion are also described.     

Tillage methods and soil and water conservation in southern Brazil

The intensive tillage systems adopted in southern Brazil have accelerated soil erosion, depleted plant-available nutrients and reduced crop productivity. These effects are better perceived in terms of farmer's land use and soil management techniques, i.e. animal- or machine-powered equipment through high and low aptitude land use classification systems. However, these tillage systems coexist together at the level of agricultural watersheds and are not compatible for continuous and sustainable agriculture. This article proposes a methodology for using agricultural watersheds as planning units for integrated soil conservation plans. This methodology is based on considerations of the farmer's socioeconomic conditions, land aptitude and other biophysical factors. The proposed methodology envisages a continuous and intensive land use for sustained production.     

Tillage methods related to soil and water conservation in south Asia

Research on different tillage systems and their role in soil and water conservation in south Asia is reviewed. Tillage has shown marked influence on soil hydraulic characteristics and to some extent on soil chemical and biological properties particularly organic matter cycling. The importance of conservation tillage in reducing runoff, soil loss and in ensuring sustainable agricultural production in the region is emphasized. The role of other tillage practices, for example contour cultivation, contour bunding, terraces and tied ridging, in increasing the profile water storage is discussed.     

Tillage systems and soil properties in West Africa

West African soil resources have high potentials for enhancing agricultural productivity, if well-managed and restored. In this context, the importance of tillage systems have not been fully appreciated as an integral part of good farming systems in order to tally with the peculiarities of the soil, crops and the environment. Most improved tillage systems are not widely used, although the relatively small-scale uncontrolled application of mechanical tillage has had untold adverse effects on properties and productivity of soils in the humid and subhumid regions.

In contrast, mechanical soil tillage involving deep plow-till and soil inversion has proven beneficial on compact soils of arid and semi-arid regions. The plow-based systems not only reduce soil bulk density and soil strength but also improve the efficiency of water and nutrient use.

The exposure of structurally unstable Alfisols and Ultisols predominant in the humid and sub-humid regions by mechanical tillage can cause more adverse effects than beneficial effects on soil properties and crop yields, especially on a long-term basis. On the other hand, the no-till system with crop residue mulch can maintain favorable soil properties. The conservation tillage system, however, requires more research to make it applicable to diverse soil types, crops and ecoregions.

Apart from the long-term effects of tillage on the level of soil organic matter and the attendant release of nutrients, the effects of tillage systems on the chemical properties of soil are often contradictory and are confounded by many other factors so that clear-cut cause and effect relationships are not obvious. The interactions between fertilizer application, liming, soil organic matter content and tillage systems, especially on acid soils, are such examples. More detailed studies on nutrient dynamics under different tillage systems are necessary. The interactions between the relatively new technologies of alley cropping and agroforestry which allow a more continuous use of the land should be investigated vis-à-vis tillage systems.

Long-term, well-designed, adequately equipped experiments (which are scanty in West Africa) should be encouraged to elucidate and confirm results of many short-term experiments.     

Tillage and soil physical properties in semi-arid West Africa

In the semi-arid zone of West Africa, the growth of annual crops is severely constrained by soil and climatic conditions. Soil physical properties, specifically low porosity resulting from the particle-size distribution and predominantly low-activity clay, restricts root system development and crop growth. Using intensive mechanical tillage is an effective method in enhancing soil porosity and physical properties.

This paper summarizes the results of tillage experiments conducted for about 30 years in West Africa. Tillage methods evaluated involved deep plowing with motorized equipment or animal powered tools using tined equipment and ridgers for earthing up. Soil properties and plant characteristics evaluated were porosity, root development, microbial life, soil-water reserves, and crop yields. Results of no-tillage and minimum-tillage studies are also discussed. Application of reduced tillage techniques did not produce satisfactory results. Several mulch farming systems, using dead or living vegetative covers, were also tested in regions where annual rainfall exceeds 1000 mm.

The results obtained support the conclusion that soil tillage is an excellent means of improving soil physical properties and crop yields in the semi-arid regions of West Africa. However, adaptation of this technique by resource-poor small farmers poses several technical and logistical problems.     

A review of tillage methods and soil and water conservation in southern Africa

Population pressures within southern Africa are forcing people to increasingly crop land of a diverse and fragile nature where the risk of environmental degradation is high and current yields are low. Much of the earlier tillage research is not applicable to these conditions as efforts have concentrated on commercial farming with tractors for the higher potential regions. It is only in the last 10–20 years that attention has increasingly focused on the tillage requirements of small-scale farmers in these harsh water-scarce semi-arid regions. There is now a clearer understanding of the basic environmental constraints to crop production in terms of climate, poor soil fertility and structure and considerable advances have been made towards improved systems but there is still a lack of appropriate tillage system recommendations. All too frequently researchers have omitted the farmer input from their considerations and endeavours. Consequently limited consideration has been given to the social (e.g. land tenure), economic (e.g. credit), energy (labour and draught power) and technical constraints experienced by the small farmers they are trying to help.

The need to develop more adoptable interim systems is therefore indicated but the slim margins within which small farmers must operate highlight the continuing need for sound tillage research to backstop the development of sustainable conservation systems.     

Tillage systems and soil compaction in Africa

Introduction of mechanized agriculture induces profound changes in soil characteristics. Soil compaction originating from mechanical land clearing, mechanized cultivation, and continuous cropping is aggravated by crusting and hard-setting phenomena of soils, and widespread occurrence of naturally compacted upland soils and subsoil gravel horizons. Natural and anthropogenically induced soil compaction has detrimental effects on growth and yields of a wide range of crops. Furthermore, compaction can persist for a long time if no adequate measures are taken to minimize or alleviate it.

In humid and subhumid regions of Africa, the no-tillage system with crop residue mulch is an important method of controlling soil compaction, followed in significance, by biological and mechanical loosening where motorized land clearing is the causative agent. Biological methods involve cover crops and alley cropping or agroforestry. Where new land areas need to be opened up, land clearing should be done by the slash-and-burn method, so that most of the nutrients in the vegetation are returned to the soil. Where mechanical land clearing is inevitable, forest removal should be done by the use of shear blade, whereby most of the roots and stumps are left in the ground intact, and the forest litter is not removed.

In semi-arid and arid regions of Africa, alleviation of soil compaction can be done by two methods. One method is to use the controlled traffic tillage system. Controlled traffic results in both a loose-rooting zone and a firmed traffic lane, thereby providing good plant growth and trafficability for timely field operations. The second method is to use mechanical loosening techniques, i.e. ploughing by animal traction or tractor power, chiseling, deep ripping, subsoiling, and tied-ride system. The effect of mechanical loosening, however, tends to be of short duration if the ensuing field traffic is not controlled.     

Tillage systems and soil properties in east Africa

This paper defines tillage, indicating that as it is mostly a physical concern of the soil, it has not been studied as much as chemically related soil properties. Tillage in shifting cultivation is also reviewed. Different tillage systems in a number of east African Countries namely Tanzania, Malawi, Botswana, Kenya, Zambia and Uganda are reviewed. The types of tillage in their respective soils are discussed in each Country. Uganda's tillage practices for the main food crop (banana) are discussed, pointing out the crop's rooting system in relation to the heavy, relatively fertile soils, where the bananas are mostly grown. The paper distinguishes between tillage to avoid soil compaction and tillage to reduce soil crusting or hardening and concludes that more research should be carried out on tillage practices relating to heavy soils as it affects the different types of crops, as most of the previous tillage research had been carried out on relatively light soils. Soil crusting or hardening which may involve an understanding of the physical, chemical and biological properties of the soil, should also receive more attention.     

Tillage implement disturbance effects on soil properties related to soil and water conservation: a literature review

The effects of tillage implement distrubance on the physical properties of soil have been widely studied. However, because soil properties resulting from the use of a given implement vary due to implement factors (depth and speed of tillage) and soil factors (water content, texture, residue cover, etc.), soil properties for a given operation are difficult to visualize, let alone predict. This report summarizes the ranges of selected soil property responses observed in previous tillage studies and identifies factors that must be considered in developing useful models to predict the effects of tillage on soil properties that are related to soil and water conservation. Considered are soil mechanical properties (surface micro-relief, aggregate size distribution and bulk density) and hydraulic properties and processes (water retention, saturated conductivity, infiltration and evaporation). For future literature reports on tillage to be useful for developing comprehensive relationships between tillage and soil properties, the reports should include information on: soil classification, texture, water content (or time of precipitation), bulk density, mechanical impedance and organic matter concentration; tillage method, depth and speed of operation; previous crop, including availability of crop residues; and previous soil management history (compacted soil, irrigated or dryland, etc.).     

Tillage and water conservation: experience in the Pacific Northwest

Abstract. Tillage practices for water conservation in the Pacific Northwest, USA, wheat region emphasize the infiltration and retention of winter rain and snow and suppression of evaporation and transpiration by weeds. The wheat-fallow system dominates in the semi-arid areas and winter wheat-spring crop rotations are most common in the sub-humid areas. The main features of water conservation during the fallow season include chisel ploughing in the autumn to reduce winter runoff, and spring and summer tillage to kill weeds, minimize evaporation, and conserve seed-zone water. Water in the seed zone is conserved by establishing a soil mulch having properties that thermally insulate the seed zone while at the same time restricting upward liquid and water vapour flow. Water conservation in the more humid zones involves chisel ploughing in autumn, uphill ploughing, and stubble retention to reduce winter runoff. New practices include minimum tillage and no-till planting methods which maintain surface residues. However, heavy equipment associated with current trends in no-till is causing soil compaction which may decrease infiltration rates. Methods under experimentation to improve infiltration with conservation tillage systems include slot mulching, paraplowing, and the use of basin pitters.     

水土保持生态服务功能评价方法

 由于生态系统服务功能支撑与维持着地球生命系统的平衡与稳定,因此它已受到当今世界普遍关注。在我国水土流失严重的情况下,运用生态服务功能理论可以正确评价水土保持措施的作用,并为合理的生态建设规划提供依据。本文在总结Costanza等人理论的基础上,分析水土保持各项措施对保护和改良人类赖以生存的自然环境条件的综合效用。认为水土保持生态服务功能包括保护和涵养水源、保护和改良土壤、固碳释氧、净化空气和防风固沙等功能。另外,本文从水土保持工程措施、水土保持农业措施和水土保持林草措施3个方向为上述功能筛选了10个评价指标,且为各个指标分别建立了评价方法。这些指标及方法将有助于对水土保持措施的生态环境效应进行深入的分析与评价。     

水土保持功能评价及其在水土保持区划中的应用

随着国家对生态文明建设的日益重视,以及国家及地方主体功能区规划的实施,对于水土保持的功能研究也越来越多.结合全国水土保持规划工作的需要,提出水土保持功能的概念、类型确定原则和功能类型,阐述了水土保持基础功能和社会经济功能的评价方法,以及各基础功能的评价指标体系.以太行山东部山地丘陵区为例,举例说明水土保持功能评价的过程和结果.对全国水土保持区划三级区基础功能进行统计分析,明确各功能的区域比例,提出8个一级区水土保持工作主要方向,维护和提高区域水土保持功能将成为水土保持工作的重点和方向.     

Tillage practices for soil and water conservation in the semi-arid zone III. Runoff modeling as a tool for conservation tillage design

A method of runoff calculation and prediction has been developed, based on known soil properties and a probability analysis of historical rainfall data. The method provides an evaluation of the efficiency of any tillage system for conserving runoff water. It consists of four steps: (1) the infiltration characteristics of a particular soil type under a given management regime are determined with the aid of a portable rainfall simulator; (2) the long-term record of actual rainfall of the region is analyzed for storm intensity distribution; (3) runoff amounts and rates are calculated for all rain storms on record by a method which combines the soil infiltration function and storm intensity pattern; and (4) synthetic long-term runoff values are predicted by calculations based on the rainfall probability distribution.The method was verified by comparing predicted results with available data from field experiments. In addition to predicting the probability of runoff under given soil conditions, the method is useful in providing information on the amount of surface storage required for successful performance of the basin tillage (tied-ridge) system, and aids in the evaluation of the efficacy of measures for improving soil infiltrability, e.g., of amendments such as gypsum.     

试论我国水土保持监测的类型与方法

依据监测工作性质，可将我国水土保持监测划分为研究性监测、实验性监测、生产性监测和预警预报性监测4种类型。各类型相互嵌套，相互依存；因此，实践中，要正视发展现状，辩证分析水土保持监测各类型间的关系，准确定位，把握正确方向，在加强监测理论和实验研究的同时，加强生产实践，并健全制度，规范管理，加强人才队伍和学科建设，进一步推动水土保持监测科学、全面、可持续发展。     

水蚀区水土保持地面观测资料整编内容与方法

资料整编是水土保持监测的基础性工作.按资料的来源和属性,可将水土保持监测资料分为基础资料、观测资料、调查资料和衍生资料.水蚀区水土保持地面观测主要涉及径流小区和小流域控制站,按监测内容和对象,一般可分为影响因子、径流和泥沙观测资料整编3大类,不同资料整编内容与方法不尽相同,各有侧重.近期,应抓紧制订监测资料整编的技术标准和整编制度,规范整编行为,同时,还应加强技术培训和档案管理,提高水土保持监测资料整编的信息化和现代化水平.     

水源涵养基本功能区水力侵蚀现状分析简

针对全国水土保持区划中确定的22个具有水源涵养功能的基本功能区,利用第1次全国水利普查获取的水力侵蚀数据,分析这些区域的水力侵蚀现状.结果表明：1）水源涵养基本功能区水力侵蚀以轻中度侵蚀为主,超过80％,强烈、极强烈、剧烈面积分布较少,与全国基本状况相似;2）与第2次全国土壤侵蚀遥感调查成果相比,水源涵养基本功能区水力侵蚀整体上有所好转,水力侵蚀总面积减少3.75％,轻中度侵蚀面积大幅减少,减幅超过20％;3）水源涵养基本功能区局部地区水力侵蚀形势严峻,极强烈和剧烈侵蚀面积虽然不大,但是与第2次遥感调查成果相比,面积均有所增加,相对增幅较大,说明局部地区存在水力侵蚀恶化的现象.     

台湾水土保持的研究综述

 简要介绍台湾水土保持研究的历史沿革、水土保持局的业务职掌及组织架构、与水土保持相关的系所师资与课程分配;同时整合相关之专业领域与产业合作 ,进而提供产、管、学实质效益及更深广之贡献。     

论生态恢复与水土保持

 生态恢复是研究生态整合性的恢复和管理过程的科学,现已成为世界各国的研究热点。目前,恢复已被用作一个概括性的术语,包括重建、改建、改造、再植等含义,一般泛指改良和重建退化的生态系统,使其重新有益于利用,并恢复其生物学潜力。生态恢复的原则包括自然法则、社会经济技术原则和美学原则。我国的水土保持小流域治理是通过工程的手段进行生态恢复的典范。水土保持小流域治理应以生态经济系统理论作指导,正确处理好人口再生产、自然再生产和经济再生产三者之间的关系,才能真正做到人与自然的和谐共处。水土保持小流域治理的方法是系统工程方法,包括综合调查与系统诊断、模型开发与治理规划、防治体系与模式设计、组织机构与运行机制等方面的内容。我国的水土保持工作亟需开拓创新,创新是水土保持工作的灵魂。只有认真纠正目前水土保持工作中存在的2种偏向,全面贯彻人与自然和谐共处的发展方针,把当地人民群众的社会需求与水土保持工作有机结合起来,才能实现“山川秀美”的宏伟目标。