• Authors:
    • Heddadj, D.
    • Cloarec, M.
  • Source: Options Mediterraneennes. Serie A, Seminaires Mediterraneens
  • Issue: 96
  • Year: 2011
  • Summary: An experimental device has been set up for ten years at the Kerguehennec Experimental Station (Chambre Regionale d'Agriculture de Bretagne) located in Brittany (western France) on the basis of a corn/wheat/rape/wheat rotation. The study, in the western context of France, compares three tillage practices (moldboard plowing, surface tillage and no-tillage) and two nutrient sources (mineral and poultry manure), each management systems repeated three times. The aim of this study was to evaluate the effect of reduced tillage and manure fertilization on the evolution of soil characteristics: porosity, aggregate stability, organic carbon, hydraulic conductivity and earthworm populations. The results show that treatments without plowing know a decline of global porosity on the layer 0-25 cm, particularly in the case of the no-till. Although the abundance and biomass of earthworms are increased in reduced tillage, the decrease of porosity is not compensated. The consequence is the decline of hydraulic conductivity, in the case of the no-till. Surface tillage seems to constitute the best compromise, because it maintains or improves the infiltrability thanks to the improvement of aggregate stability in the surface layer and the protection of soil surface by the presence of a mulch.
  • Authors:
    • Avci, M.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 2
  • Year: 2011
  • Summary: Central Anatolian soils have high risk of erosion, degradation and intensive cultivation. Consequently, they are in danger of exhausting their agricultural use unless conservation agricultural practices are adopted. Conservation agriculture is a key tool in sustainable production systems throughout the world and is developed around soil management technology that minimizes soil disturbance, maximizes the soil cover and promotes crop diversity to offer benefits to farmers and to the environment. It has been particularly effective at sustaining crop production in semi-arid rain-fed regions such as the Central Anatolian soils, where potential evaporation exceeds precipitation during most months of the year, dry farming is extensively practiced, water and wind erosion is common, and proper application of water- and soil-conserving tillage technology is critical. The area under plow expanded its limits as the number of tractors in agriculture dramatically increased in the 1960s. This is the starting point for inappropriate use of the agricultural land. The conservation agricultural technologies, therefore, are of utmost importance for the region. Common farmers' practices of a fallow-wheat system in the central plateau of Turkey are incompatible with the conservation agriculture concept. The objective of this review is to re-evaluate the performances of the partial and full conservation tillage practices previously tried in the region. This review reached the following conclusions: (1) agreeing with the conservation principles, fall tillage as a primary operation in the fallow phase was found to be useless compared with leaving the land without tillage; (2) therefore, much research has focused on spring tillage as a primary operation and employed conventional, semi-conservative and conservative methods. Results showed that the conventional system, in addition to being ecologically unfriendly, is unprofitable as compared with other conservation practices regarding the updated cost analysis; (3) similarly, tillage depth in primary spring tillage was determined to be shallower than the depths currently practiced by farmers, in agreement with the conservation principles; (4) fallow tillage operations in summer to create dust mulch for eliminating soil moisture loss did not increase the crop yields and soil moisture as compared with chemical fallow; (5) no-till fallow was similar to the conventional clean fallow system in terms of moisture and yield levels. However, no-tillage resulted in 50% reduction in the cost of tillage besides its ecologically-friendly effects; (6) the existing dryland agricultural systems in the plateau should be transformed into or changed toward sustainable systems, although further research is required on residue and stubble management, and integrated weed control methods to drill the soil with high amounts of residue on the field.
  • Authors:
    • Attard, E.
    • Recous, S.
    • Chabbi, A.
    • Berranger, C. de
    • Guillaumaud, N.
    • Labreuche, J.
    • Philippot, L.
    • Schmid, B.
    • Roux, X. le
  • Source: Global Change Biology
  • Volume: 17
  • Issue: 5
  • Year: 2011
  • Summary: Land-use practices aiming at increasing agro-ecosystem sustainability, e.g. no-till systems and use of temporary grasslands, have been developed in cropping areas, but their environmental benefits could be counterbalanced by increased N2O emissions produced, in particular during denitrification. Modelling denitrification in this context is thus of major importance. However, to what extent can changes in denitrification be predicted by representing the denitrifying community as a black box, i.e. without an adequate representation of the biological characteristics (abundance and composition) of this community, remains unclear. We analysed the effect of changes in land uses on denitrifiers for two different agricultural systems: (i) crop/grassland conversion and (ii) cessation/application of tillage. We surveyed potential denitrification (PD), the abundance and genetic structure of denitrifiers (nitrite reducers), and soil environmental conditions. N 2O emissions were also measured during periods of several days on control plots. Time-integrated N 2O emissions and PD were well correlated among all control plots. Changes in PD were partly due to changes in denitrifier abundance but were not related to changes in the structure of the denitrifier community. Using multiple regression analysis, we showed that changes in PD were more related to changes in soil environmental conditions than in denitrifier abundance. Soil organic carbon explained 81% of the variance observed for PD at the crop/temporary grassland site, whereas soil organic carbon, water-filled pore space and nitrate explained 92% of PD variance at the till/no-till site, without any residual effect of denitrifier abundance. Soil environmental conditions influenced PD by modifying the specific activity of denitrifiers, and to a lesser extent by promoting a build-up of denitrifiers. Our results show that an accurate simulation of carbon, oxygen and nitrate availability to denitrifiers is more important than an accurate simulation of denitrifier abundance and community structure to adequately understand and predict changes in PD in response to land-use changes.
  • Authors:
    • Baraibar, B.
    • Ledesma, R.
    • Royo-Esnal, A.
    • Westerman, P. R.
  • Source: Crop Protection
  • Volume: 30
  • Issue: 9
  • Year: 2011
  • Summary: Harvester ants from the species Messor barbarus (L.) are important seed predators in semi-arid cereal fields of NE Spain, and can contribute substantially to weed control. However, occasionally they harvest newly sown crop seeds at sowing in autumn, or ripe cereal grains close to harvest in summer, causing yield losses. A preliminary study was conducted in 34 commercial winter cereal fields to measure yield loss, and to identify factors that influence it. The area affected by ants was measured ten days prior to the anticipated harvest date. Ant colony size, nest density, crop height, weed densities and temperatures at sowing were assessed. At sowing, harvester ants did not cause yield losses (0.2% of potential yield on average). At harvest, yield losses were generally low as well (0.6%) although occasionally higher losses were recorded (max. 9.2%). Yield losses significantly increased with increasing nest density, nest size and with number of years of no-till. The results of this study show that in 2009 yield losses caused by M. barbarus were insignificant and more than offset by the benefits provided by the destruction of weed seeds.
  • Authors:
    • Pires, L. F.
    • Nova, N. A. V.
    • Pereira, A. B.
    • Alfaro, A. T.
  • Source: Revista Brasileira de Meteorologia
  • Volume: 26
  • Issue: 2
  • Year: 2011
  • Summary: The uptake of water from the roots of crops comes to being a physiological response of the plant to the water loss process through its stomata. Getting to know the daily transpiration rates throughout the phenological cycle allows for the application of the ideal amount of irrigation water at the right moment to maximize production with environmental protection. Since transpiration direct measurements at the field, mainly for trees in general, are to be of operational difficulty and relatively high cost we came up with a methodology that allows one to calculate the daily transpiration rates of apple trees and citrus orchards from variables of both the physical environment and the crop. The input data of the proposed model are air temperature, air relative humidity, photoperiod duration, and leaf area. Estimated transpiration rates based on the water potential gradient between the air and leaf approach were comparable in apple trees and citrus orchards. Sap flow daily values were obtained by means of the heat balance method at Bordeaux, France, and Piracicaba, SP, Brazil. All the coefficients of determination of the regression equations obtained herein were higher than 0.93. This allows one to calculate the amount of irrigation water to be applied throughout the crop growing seasons with a high precision as a function of meteorological data and crop covering density at the sites in the study.
  • Authors:
    • Villar, H. L.
    • Sakai, E.
    • Bodine Junior, D.
    • Pires, R. C. de M.
    • Silva, T. J. A. da
    • Arruda, F. B.
  • Source: Engenharia Agrícola
  • Volume: 31
  • Issue: 6
  • Year: 2011
  • Summary: The aim of this study was to evaluate the effect of different microirrigation designs on root system distribution in wet bulb region, orange orchard yield and quality of orange fruits. The experiment was installed as random blocks with five treatments and four replicates in an orchard of 'Pera' orange trees grafted on 'Cleopatra' mandarin rootstock. The treatments consisted of: one drip line (T1), two drip lines (T2), four drip lines (T3) per planting row, microsprinkler irrigation (T4) and without irrigation (T5). Irrigation treatments favored yield and degreesBrix. The treatment with a single drip line (T1) showed the greatest quantity of roots in relation to the treatments T2 and T3.
  • Authors:
    • Yahuza, I.
  • Source: International Journal of Biosciences (IJB)
  • Volume: 1
  • Issue: 5
  • Year: 2011
  • Summary: Intercropping (growing two or more crops together simultaneously) is increasing being adopted worldwide, probably because there have been suggestions that the system is beneficial in terms of land use efficiency compared to sole cropping. There are several indices for estimating intercrop performance compared to the component sole crops, but as reviewed in this paper, the land equivalent ratio (LER) is the most widely adopted. Yet the LER is constrained because it is not able to account for the relative duration each component in the intercrop spent in the field may have had on intercropping performance. Area time equivalency ratio (ATER) appears to have solved this problem well. However, neither ATER nor LER can account for the physiological or physical basis for the intercropping performance. The crop performance ratio (CPR) is more appropriate in this regard, even though CPR 'adjusted for time', (CPRT) is more efficient where the component crops differ in growth duration. In addition, particularly for intercrops with commercial value, there may be a need to compute a monetary advantage (MA) for intercropping. This paper concludes that in addition to the LER, for certain intercrops such as wheat/faba bean system that has not been widely adopted, there may be a need to use other indices such as ATER, CPR, CPRT and MA as may be applicable in order to understand more fully the nature of intercrop benefits that may exist. Indeed such type of information may help to attract potential growers.