Crop production through conservation-effective tillage in the tropics

Agriculture can be intensified and food production increased in the tropics through conservation-effective tillage, with other benefits being soil and water conservation, energy saving and improved timeliness of planting.

The agronomic and economic performance of conservation-effective tillage is extremely location-specific. Problems important in semi-arid regions may not be significant in humid tropical areas. This paper attempts to avoid broad generalizations and to indicate ways of developing the best combination of practices for each local situation. The widespread use of on-farm research and demonstration plots to obtain site-specific information would aid the rapid adaptation and adoption of conservation farming practices in developing countries within different regions. Acceptance of conservation tillage by small farmers in developing countries would be an evolutionary process, and their adoption of improved simple farm equipment and appropriate practices to control weeds should be intesively promoted.

A concerted effort to understand and respond to the needs of farmers, crops and soils will be essential in achieving the goal of increasing agricultural productivity while maintaining oil through conservation-effective tillage in the tropics.     

Crop production in the tropics: A review

Intensive land use and concomitant land degradation are strongly undermining the sustainability of current crop production systems in the tropics. Thus, finding alternative cropping strategies to overcome soil and environmental stresses is an integral part of the ongoing process of maintaining and improving crop productivity. In this paper, major features of crops and crop production systems were reviewed. Production systems such as pastures, perennial crops, and agroforestry were found to be highly effective in promoting high and stable crop productivity, restoring and/or enhancing soil fertility, and minimizing erosion risk.     

Potato production in the tropics: Crop requirements

Considerable efforts have been made to alleviate constraints affecting potato production in the tropics. In spite of substantial progress, particularly in the area of plant breeding, overall yield increase due to this improved technology has been marginal at best. The major factor restricting production appears to be the limited adaptation of potato to tropical conditions. Also, the lack of a clear understanding of the requirements of the crop hampers a more efficient use of the available technology. As a partial answer to these concerns, this paper reviews current knowledge on the environmental, soil physical and soil chemical requirements of potato in tropical regions.     

Soil management options for Alfisols in the semi-arid tropics: annual and perennial crop production

A field experiment was conducted in the semi arid tropics to study the effects of soil structural modification on cropping systems. The aim was to improve crop production and land resource protection using innovative soil management practices. Tillage, mulch and perennial/annual rotational based systems were compared for 5 years in an Alfisol at ICRISAT in India. Crop yield parameters, including grain and biomass yield, leaf area index, crop cover, and plant height were measured. Results indicate significant benefits to annual crop yield (maize, sorghum) from improved water supply due to mulching with farmyard manure or and rice straw, and due to rotation with prior-perennial crops. Grain yields were 16 to 59% higher in mulched treatments compared to unmulched treatments, with similar increases for fodder yields. Annual crop yields after 4 years of perennials were 14 to 81% higher than unmulched treatments, except for low fertility maize grown after buffel grass. The interaction with chemical fertility was less clear than for water supply. The results have implications for soil management throughout the semi-arid tropics.     

不同生产目标条件的马铃薯水氮管理优化

基于不同生产目标,优化不同降水年型下的水氮耦合方案对马铃薯生产的可持续发展具有重要意义。该研究基于中国北方农牧交错带地区27个站点的气象数据、土壤数据和管理数据驱动APSIM-Potato模型,设置不同的灌溉和氮肥耦合情景,基于土壤水分亏缺量设置灌溉情景（共设置10个灌溉梯度,即土壤水分亏缺范围为10～100 mm,间隔10 mm）,施氮肥量为30～210 kg/hm2,梯度为30 kg/hm2,模拟分析不同降水年型下水氮耦合对马铃薯产量、水分利用效率和经济收益的影响,并推荐不同降水年型下获得不同生产目标的最佳水氮耦合方案。结果表明：农牧交错带干旱年型、正常年型和湿润年型下不同水氮耦合方案的马铃薯最高产量分别为30 200～39 400、28 900～38 800和27 000～38 000 kg/hm2,其中干旱年型下产量最高。干旱年型、正常年型和湿润年型下获得最高产量的灌溉量分别为589、544和512 mm,氮肥投入量均为最大值,即210 kg/hm2。干旱年型、正常年型和湿润年型下不同水氮耦合方案的马铃薯最高水分利用效率分别为85.9、90.2和92.2 kg/(mm·hm2),获得最高水分利用效率的灌溉量分别为172、107和87 mm,氮肥投入量均在60～120 kg/hm2之间,其中干旱年型下投入量为60 kg/hm2的站点比例最高。干旱年型、正常年型和湿润年型不同水氮耦合方案下马铃薯的最高收益分别为19 340、18 610和18 470元/hm2,获得最高收益的灌溉量分别为226、152和116 mm,干旱年型和正常年型获得最高收益的氮肥投入量均在30～90 kg/hm2之间,湿润年型下获得最高收益的氮肥投入量在60～90 kg/hm2之间。研究结果有助于当地生产者基于不同的生产目标制定较优的水氮管理方案。     

The search for carbon sinks in the tropics

The study and modeling of the global C cycle have been dominated by the assumption that the atmosphere and the biota were in C steady state prior to the industrial revolution. This view led to the perception that most of the terrestrial biota was neutral with regards to the C concentration of the atmosphere. Recent evidence suggests that neither the atmosphere nor the biota were in C steady state prior to, or since, the industrial revolution. Therefore, it is now necessary to re-visit the role of natural processes in the global C cycle, study the C cycle in its totality, and focus attention on the magnitude of potential C sinks in ecosystems previously thought to be neutral with respect to atmospheric C. “An improved understanding of the CO₂ cycle is essential to predict the future rate of any atmospheric CO₂ increase and to plan eventually for an international CO₂ management strategy” Tans et al. (1990).     

Life cycle greenhouse gas emissions from five contrasting rice production systems in the tropics

Carbon footprint (CF) quantification of major rice production systems (RPSs) is a prerequisite for developing strategies for climate change mitigation in agriculture. Total life cycle greenhouse gas emissions (LC-GHGs) from rice production to consumption might provide precise CFs for RPSs. Therefore, we assessed three segments (pre-farm, on-farm, and post-farm) of LC-GHGs under five major contrasting RPSs, i.e., aerobic rice (AR), shallow lowland rice(SLR), system of rice intensification (SRI), ...     

Rainfall simulator for tillage research in the tropics

A new concept is proposed that enables rainfall simulation to be carried out in the tropics, where technical facilities and know-how are usually limited. A rainfall simulator developed on the basis of this concept produced uniform rainfall intensities (uniformity coefficient, C_u, 0.8–1.0) of 4–5, 5–6, 6–7 and 7–8 mm/h on areas of 131, 88, 25 and 8.6 m², respectively. Possibilities of using the rainfall simulator for erosion research are discussed.     

Tillage systems for root and tuber crops in the tropics

Although limited information is available on tillage practices for root crops, published results show that tillage methods vary widely depending upon the specific root crop, the soil type, the previous vegetation, as well as the socio-economic conditions of farmers. These aspects are discussed in this review.

In general terms, it has been found that root and tuber crops are sensitive to soil compaction, inadequate aeration or poor drainage and therefore respond favorably to intensive tillage, followed by ridging or mounding. However, large differences exist between crops, with potato, sweet potato and yam requiring more intensive cultivation than cassava and taro. On light-textured soils, cassava can be grown without or with minimum tillage as long as weeds are controlled; in heavy or compacted soil cassava responds favorably to tillage and yields tend to increase when grown on ridges. In order to reduce erosion as well as production costs, cassava should be grown with as little tillage as possible as long as high yield can be maintained. Contour ridging and mulching are other practices that not only tend to increase yields but also reduce erosion losses.

Organized data for use in a classification of the tillage requirements of different soils for the various root crops is lacking. We suggest that research efforts should be directed towards the characterization of the physico-chemical and biological factors which determine the tillage requirements of a given soil for a given root crop.     

Balanced and integrated nutrient management for enhancedand economic food production: case study from rainfed semi-arid tropics in India

Soil degradation in the semi-arid tropics (SAT) is mainly responsible for low crop and water productivity. In Madhya Pradesh and Rajasthan states in India, the soil analyses of farmers’ fields revealed widespread deficiencies of S (9–96%), B (17–100%) and Zn (22–97%) along with that of P (25–92%). Soil organic C was deficient in 7–84% fields indicating specifically N deficiencies and poor soil health in general. During on-farm evaluations in rainy seasons 2010 and 2011, the soil test based addition of deficient nutrient fertilizers as balanced nutrition (BN) increased crop yields by 6–40% (benefit to cost ratios of 0.81–4.28) through enhanced rainwater use efficiency. The integrated nutrient management (INM), however, decreased the use of chemical fertilizers in BN by up to 50% through on-farm produced vermicompost and recorded yields at par or more than BN with far better benefit to cost ratios (2.26–10.2). Soybean grain S and Zn contents improved with INM. Applied S, B, Zn and vermicompost showed residual benefits as increased crop yields for succeeding three seasons. Hence, results showed INM/BN was economically beneficial for producing more food, while leading to resilience building of SAT production systems.     

湖北省红薯生产现状及高产平衡施肥研究

调查表明,湖北省红薯施用化学氮(N)、磷(P2O5)肥分别平均为132.0kg/hm2和43.5kg/hm2,基本不施用化学钾肥和微量元素肥料.研究结果表明,平衡施肥可以促进红薯获取高产,氮磷钾肥施用比例(N:P2O5:K2O)以1:0.4～0.5:0.8～1.0为宜,其中氮肥(N)用量以150～225kg/hm2、钾肥(K2O)以120～225kg/hm2为好,氯化钾可以作为红薯钾肥来源,同时应根据实际情况配合施用锌、钼等微量元素肥料.     

Impact of crop production system on the content of macronutrients in potato tubers

ABSTRACT

The content of macronutrients in potato tubers arouses interest because of their substantial consumption in the world and significant role in elements' budget in human diet. The research objective has been to evaluate the content of macronutrients in tubers of potatoes grown in different systems of crop production in Poland. In 2012–2014, an experiment was conducted to test potato cultivation in three-crop production systems: conventional, integrated and organic. In each of the six-field crop rotation systems, there were five potato cultivars classified into different earliness groups. The following macronutrients in dry mass of potato tubers were determined: N, P, K, Ca, Mg, Na, S and Cl, and the various ratios between them were calculated. The research carried out proved that potatoes production systems affect the chemical composition of tubers, which is additionally modified by whether condition and genetic features of cultivars. Potato tubers from organic farming contained by about 20% less N than tubers from conventional or integrated systems. Potato tubers from organic production system displayed lower content of Ca and Na in comparison with the conventional and integrated systems. The least of P and S were detected in tubers of the potatoes grown conventionally.     

Crop evapotranspiration of chilli in the tropics

Abstract

The rate of crop evapotranspiration though can be predicted theoretically but the actual field study would give a more accurate data. Result from a simple lysimeter study showed that the daily rate of actual crops evapotranspiration, ETa of chilli (Capsicum annum) under the tropical condition was in the range between 4.94–7.72 mm. Their actual crop evapotranspiration/ reference crop evapotranspiration ratio, ETa/ETo ratio was between 0.94 to 1.76 depending on the growth stages of the crops. The estimated monthly value of ETo using Blaney‐Criddle was about 5 mm/day.     

The effect of subsoiling and irrigation on potato production

Thin tillage pans restrict water movement and potato (Solanum tuberosum L.) root penetration in fine-textured soils of the Columbia Basin in central Washington State, U.S.A. Deep chiseling beneath potato rows, with simultaneous deep incorporation of fertilizer, was used to break-up the pans, enabling deeper root development. The effects of subsoiling on soil physical conditions and on potato production were examined under varying rates of irrigation. Deep tillage decreased soil strengths and bulk densities and increased porosity to depths of 10–16 cm below the pans. These improved subsoil physical conditions resulted in deeper root penetration, but the additional rooting only amounted to a small increase to the total root system. Cubic polynomial regressions demonstrated that subsoiling significantly increased potato yields under very droughty conditions but had no significant effects at intermediate (near optimum) levels of water application. Potato quality (percentage of U.S. No. 1 grade tubers and tuber specific gravity) was generally unaffected by deep tillage. These results indicate that, for potatoes, appropriate irrigation management can be used to overcome problems of restricted root penetration and impeded water movement caused by tillage pans.     

An evaluation of cation exchange capacity measurements for soils in the tropics

Abstract

Comparisons of CEC and exchange acidity neasurements were made on a group of selected West African soils using three commonly used analytical procedures, namely, neutral‐acetate displacement, BaCl₂‐TEA leaching at pH 8, and unbuffered KCl extraction.

The three methods gave large differences in CEC values which followed the order of BaCl₂‐CEC>>NH₄OAc‐CEC> KCl‐CEC. Results of exchange acidity also followed the same order. The high exchange acidity values obtained by the BaCl₂‐TEA (pH 8) method were mainly due to changes in surface charge characteristics of Fe and Al oxides and hydrous oxides. The effective CEC method is recommended for routine soil analysis for highly weathered soils in the tropics.

Regression analysis of the base saturation values obtained from the three methods indicated the data followed a curvilinear relationship. The acetate method was more highly correlated with the effective CEC method than with the BaCl₂ method.     

Tillage systems and soils in the semi-arid tropics

Even though conservation tillage may be ideal for the semi-arid tropics (SAT) in view of results from studies and tillage practices in the U.S.A. and Australia, studies conducted in semi-arid regions of Africa appear to support the use of conventional tillage systems. Some of the reasons for this apparent discrepancy are because of the physical properties of the soils in semi-arid Africa, particularly the Sahelian zones where the soils are sandy, have high bulk densities and therefore low total porosities and form crusts upon wetting and drying. Consequently, no-till or reduced tillage systems that do not have the soil surface covered by residue in irder to prevent formation of crust as a result of raindrop impact, tend to lose water through runoff in a region where water economy is essential. Also, because these soils have inherently high bulk densities, conventional tillage systems appear to be suitable since they increase the macropores, reduce both bulk density and strength and thus ensure prolific root distribution and the resultant exploration of water and nutrients at greater soil depths. Notwithstanding, it seems that since most of the SAT soils are structurally unstable, further conventional tillage even though it has ephemeral advantages, may in the long term be exacerbating the problems of structural instability and their deleterious effect on water and soil conservation and therefore on crop production. We suggest that at this stage soil tillage research in the semi-arid regions of Africa and Asia should re-examine some of the concepts of conservation tillage in relation to soil physical properties and processes in order to obtain a tillage system that ensures high crop yields without destruction of the soil resource.     

互花米草与土豆混合厌氧发酵产酸和产沼气特性（英）

研究了中温（35℃）批量发酵条件下互花米草与土豆VS配比分别为6∶1、7∶1和9∶1时混合厌氧发酵的产酸发酵和产沼气特性。试验结果表明：1）与互花米草单独发酵时的丙酸型产酸发酵不同,混合发酵的产酸发酵表现为丁酸型发酵;混合发酵时发酵液中总挥发性有机酸（TVFAs）的浓度比互花米草单独发酵时提高了1倍多;混合发酵时发酵液中各单一有机酸浓度依次为乙酸>丙酸>丁酸,而互花米草单独发酵时为丙酸>乙酸>丁酸;2）6∶1、7∶1和9∶1三种配比下的沼气产量分别为460、431和415 mL/g VS,比互花米草单独发酵时的361 mL/gVS分别提高了27.4%、19.3%和15.0%;3）6∶1、7∶1和9∶1三种配比下的沼气中的甲烷含量分别为60.3%、62.4%和62.7%,比互花米草单独发酵条件下57.4%的平均甲烷含量提高了大约3%～5%。总之,混合发酵显著改变了互花米草的产酸发酵特性,这些改变对促进互花米草的厌氧发酵和提高所产沼气的质量均具有积极的意义。