Conservation agriculture in the dry Mediterranean climate

The objective of this article is to review: (a) the concepts and principles that underpin Conservation Agriculture (CA) ecologically and operationally; (b) the potential benefits that can be harnessed through CA systems in the dry Mediterranean climates; (c) current status of adoption and spread of CA in the dry Mediterranean climate countries; and (d) opportunities for CA in the Central and West Asia and North Africa (CWANA) region. CA, comprising minimum mechanical soil disturbance and no-tillage seeding, organic mulch cover, and crop diversification is now practised on some 125 million ha, corresponding to about 9% of the global arable cropped land. Globally, the area under CA is spread across all continents and all agro-ecologies, including the dryland climates in the Mediterranean basin region as well as in the Mediterranean climates elsewhere in the world. Worldwide empirical and scientific evidence is available to show that significant productivity, economic, social and environmental benefits exist that can be harnessed through the adoption of CA principles for sustainable production intensification in the dry Mediterranean climates, including those in the CWANA region. The benefits include: fundamental change for the better in the sustainability of production systems and ecosystem services; higher stable yields and incomes; climate change adaptation and reduced vulnerability to the highly erratic rainfall distribution; and reduced greenhouse gas emissions. CA has taken off globally and is now spreading in several Mediterranean climates outside the Mediterranean basin particularly in South America, South Africa and Australia. In the dry Mediterranean climates in the CWANA region, CA is perceived to be a powerful tool of land management but CA has not yet taken off. Research on CA in the CWANA region has shown that there are opportunities for CA adoption in rainfed and irrigated farming systems involving arable and perennial crops as well as livestock

Symbiotic nitrogen fixation : prospects for enhanced application in tropical agriculture

In addition to their Nitrogen (N2)-fixing capacity legumes are extremely important in human and animal diets, significantly improving household health standards. This book is based on the proceedings of the workshop (“International Workshop on Biological Nitrogen Fixation for Increased Crop Productivity, Enhanced Human Health and Sustained Soil Fertility,” 2002, at ENSAM-INRA, Montpellier, France), takes a holistic approach to harnessing legume Biological Nitrogen Fixation (BNF) technologies, starting from a socioeconomic perspective, and progressing to agronomic and genetic options, bringing together innovative aspects and participatory research strategies

Atmospheric CO2 increase benefits symbiotic N2 fixation by legumes under drought

Leguminous plants are considered to have a competitive advantage under global climate change because of increased rates of symbiotic nitrogen (N2) fixation in response to increased atmospheric CO2. However, this hypothetical advantage may not be realized under actual climate change due to the associated increase in frequency and duration of drought, as N2 fixation in legume species such as soybean is sensitive to soil drying. Yet, it has been discovered that N2 fixation in soybean becomes drought-tolerant under increased CO2 concentration. The reduced susceptibility of N2 fixation to drought was associated with an increase in total nonstructural carbohydrates and a decrease in ureides in leaves. These results empirically indicate that legumes will have substantial comparative advantage over cereals under climate change

Calidad de fruto y aceite de olivos maduros en condiciones de cultivo de secado parcial de la zona radical

This study was conducted to evaluate the quantitative and qualitative effects of partial rootzone drying (PRD) irrigation on olive trees and their fruit and oil quality. Olive trees of the Moroccan Picholine variety were grown under arid conditions in Marrakech, and exposed to four irrigation treatments: Control (irrigated with 100 % of the crop evapotranspiration, on the two sides of the root system), PRD1 (irrigated with 50 % of the control, on one side of the root system, switching every two weeks), PRD2 (irrigated with 50 % of the control, on one side of the root system, switching every four weeks) and PRD3 (irrigated with the same amount of water as the control applied on one side of the root system, switching every two weeks). The individual fruit weight, dimensions and oil contents were generally greater under PRD than the control. Whereas, the fruit water content was lower under PRD1 and PRD2 than the control and PRD3. Oil acidity was not affected by irrigation, while the total polyphenol content, which affects the oxidative stability and sensory characteristics of the oil, increased in response to the PRD irrigation, especially under PRD1 (246.0 ppm) and PRD2 (278.5 ppm) treatments, against 148.4 ppm and 101.8 ppm for PRD3 and the control respectively. This increase could explain the oil bitterness observed under PRD1 and PRD2. The fatty acid composition was not affected by PRD1 and PRD2. The oil quality based on UV absorption coefficients (K232 and K270) decreased significantly under PRD2. Chlorophyll content and maturity index were antagonistic, and olive ripeness was found to be precocious under PRD irrigation treatments compared to the control.Este estudio fue realizado para evaluar los efectos cuantitativos y cualitativos de la irrigación de olivos por secado parcial de la zona radical (PRD) sobre la calidad de su fruto y de su aceite. Los olivos de la variedad marroquí Picholine fueron cultivados en condiciones áridas en Marrakech, y expuestos a cuatro tratamientos de irrigación: Control (irrigado con el 100 % de la evapotranspiración de la cosecha, en los dos lados del sistema radical), PRD1 (irrigado con el 50 % del control, en sólo un lado del sistema radical, cambiando cada dos semanas), PRD2 (irrigado con el 50 % del control, en un lado del sistema radical, cambiando cada cuatro semanas) y PRD3 (irrigado con la misma cantidad del agua que el control aplicado en un lado del sistema radical, cambiando cada dos semanas). El peso individual del fruto, sus dimensiones y el contenido en aceite fueron generalmente mayores bajo PRD que en el control. Mientras que, el contenido de agua de la aceituna fue inferior en PRD1 y PRD2 que en el control y en PRD3. La acidez del aceite no se afectó por el régimen de irrigación, mientras que el contenido total de polifenoles, que afecta a la estabilidad oxidativa y a las características sensoriales del aceite, aumentó en respuesta a la irrigación mediante PRD, sobre todo con los tratamientos PRD1 (246.0 ppm) y PRD2 (278.5 ppm), frente a los 148.4 ppm y 101.8 ppm de PRD3 y el control, respectivamente. Este aumento podría explicar el amargor del aceite obtenida con PRD1 y PRD2. La composición de ácidos grasos no fue afectada por PRD1 Y PRD2. La calidad del aceite basada en los coeficientes de absorción UV (K232 y K270) disminuyó considerablemente con PRD2. El contenido de clorofila resultó antagonista del índice de madurez, y éste último se desarrolló más precozmente en los tratamientos de irrigación PRD que en el control

Screening sorghum germplasm for tolerance to soil salinity

Sorghum (Sorghum bicolor) is known to be relat ively more tolerant to sal ini ty than other crops, such as maize (Zea mays) or legumes and thus has the potent ial to replace maize in saline soils ( Igar tua et al . 1994). The existence of large interspeci f ic (Yang et al . 1990) and int ra-speci f ic (Maas 1985, Azhar and McNe i l l y 1988, De La Rosa-Ibarra and Mai t i 1995) var iat ion for sal ini ty tolerance of fers a scope for integrat ing these tolerant crop genotypes wi th appropriate management practices to better exploi t the saline soils

Soybean N2 Fixation Estimates, Ureide Concentration, and Yield Responses to Drought

Increasing N2 fixation tolerance to drought has been hindered by the labor and costs of quantifying N2 fixation using 15N methodologies. The relative abundance of ureides (RAU) in plant tissues has been used for estimating N2 fixation in soybean [Glycine max (L.) Merr.] grown under well-watered conditions, but it has not been evaluated for drought conditions. The present research evaluated the response of N accumulation to N fertilization, the ability of the RAU technique to predict N2 fixation under drought conditions, and the response of yield to N fertilization under well-watered and drought conditions. Under drought, shoot N accumulation rate during vegetative growth approximately doubled as the amount of N fertilizer was increased from 10 to 200 kg N ha(-1), indicating a greater sensitivity of N2 fixation to drought than uptake and assimilation of inorganic N. Under well-watered conditions, the relationship between estimates of N2 fixation made by 15N-dilution and RAU agreed within 15% of published reports. Under drought conditions, however, this relationship was greatly different (13 to 43%) from published reports. Fertilization with inorganic N in 1 yr increased grain yield 15 to 25% for the drought treatment and 12 to 15% for the well-watered treatment. In a second year, N fertilization increased yield of both drought and well-watered treatments approximately 9%. This research indicates that the RAU technique for estimating N2 fixation under drought conditions may be invalid without further refinement, that N2 fixation is more sensitive to drought than the uptake and assimilation of inorganic soil N, and that increasing the tolerance of N2 fixation to drought would likely result in yield increases

Variability of root length density and its contributions to seed yield in chickpea (Cicer arietinum L.) under terminal drought stress

The importance of root systems in acquiring water has long been recognized as crucial to cope with drought conditions. This investigation was conducted to: (i) evaluate the variability on root length density (RLD) of chickpea in the vegetative growth stage; (ii) estimate the effect of RLD on seed yield under terminal drought conditions; and (iii) set up a procedure to facilitate the screening of chickpea genotypes with large RLD. Twelve diverse chickpea genotypes were grown in tall PVC cylinders with two different soil water treatments in 2000 and 2001, and in field under water deficit conditions during 2000/2001 and 2001/2002. In field trials, the mean RLD at 35 days after sowing showed a significant positive correlation with seed yield in both years. Similarly, the RLD in the 15-30 cm soil depth had significant positive effects to the seed yield in both years. The importance of the root trait was particularly relevant in 2001/2002, a more severe drought year, when the RLD in deeper soil layer, 30-60 cm depth, showed a significant positive relationship with seed yield. Also, the RLD at deeper soil layer, 30-60 cm depth, was higher in 2001/2002 than in 2000/2001, in particular in tolerant genotypes. The PVC cylinder trials were set up to facilitate the screening of chickpea genotypes with large RLD. RLD of plants grown in cylinders with 70% field capacity was correlated with RLD in the field trials (r=0.731; p=0.01). This work highlights the importance of roots in coping with terminal drought in chickpea. The cylinder system offers a much easier procedure to screen chickpea genotypes with large RLD

Screening pearl millet germplasm for tolerance to soil salinity

Saline soils account for up to 580 million ha worldwide and are widespread In arid and semi-arid regions (Rengasamy 2002). Pearl millet [Pennisetum glaucum) is often grown In saline soils and Is known to be relatively better In tolerance to salinity than other crops, particularly maize (Zea mays) or legumes (Ashrafand McNeilly 1987, Dua 1989). However, a well-focused search can lead to the Identification of genotypes with superior tolerance. Since pearl millet Is usually grown rainfed with minimum Input, It Is all the more Important to genetically Improve the adaptation of this crop to soil salinity. The Improved salinity tolerant lines together with cultural management options provide greater scope for Improving the crop productivity in these saline soils