• Authors:
    • Rypowski, K.
    • Cortes, M.
    • Osorio, A.
    • Burgos, M.
  • Source: Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: Six tests were done to evaluate the application of irrigation rates in Limari River Valley (3036′ South Latitude 7112′ West Longitude and 218 m of altitude) in avocado and mandarin tree orchards during two agricultural seasons. Assessments were made in volumes of water applied, discharge of the drippers and irrigation frequency used. Also, the water stored in the soil profile was monitored by moisture direct sampling with drill, performed deeply and transversely to the drip lines and plantation rows. In the cases studied it was possible to appreciate a wide variety of situations regarding water stored in the profile. In the vast majority of cases, excess water conditions were found, both in the root zone and below it. In very few cases, the moisture in the root zone of trees reached levels close to permanent wilting percentage (PWP). This would reflect poor efficiency in the implementation and management of irrigation water through drip irrigation, regardless of the uniformity coefficient (UC) of drippers. This situation becomes much more problematic in those soils which present high percentages of clay; creating low aeration conditions for root development. It is also possible to observe an important deviation from moisture profiles to the lower or steeper sectors of the plantation system; generating drier soil or less humid conditions in higher zones, with a big impact on root development. When calculating the relation between the water stored in the root zone versus the total water available in the profile, results between 44 and 73% were obtained, values that reflect inefficient irrigation conditions. These results were corroborated by the high variation coefficients (VC) in the moisture content in the profile, with values higher than 19.00% and with maximum value equal to 43.64% VC.
  • Authors:
    • Hachum, A. Y.
    • Farahani, H. J.
    • Oweis, T. Y.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 8
  • Year: 2011
  • Summary: Cotton ( Gossypium hirsutum L.) is the most important industrial and summer cash crop in Syria and many other countries in the arid areas but there are concerns about future production levels, given the high water requirements and the decline in water availability. Most farmers in Syria aim to maximize yield per unit of land regardless of the quantity of water applied. Water losses can be reduced and water productivity (yield per unit of water consumed) improved by applying deficit irrigation, but this requires a better understanding of crop response to various levels of water stress. This paper presents results from a 3-year study (2004-2006) conducted in northern Syria to quantify cotton yield response to different levels of water and fertilizer. The experiment included four irrigation levels and three levels of nitrogen (N) fertilizer under drip irrigation. The overall mean cotton (lint plus seed, or lintseed) yield was 2502 kg ha -1, ranging from 1520 kg ha -1 under 40% irrigation to 3460 kg ha -1 under 100% irrigation. Mean water productivity (WP ET) was 0.36 kg lintseed per m 3 of crop actual evapotranspiration (ET c), ranging from 0.32 kg m -3 under 40% irrigation to 0.39 kg m -3 under the 100% treatment. Results suggest that deficit irrigation does not improve biological water productivity of drip-irrigated cotton. Water and fertilizer levels (especially the former) have significant effects on yield, crop growth and WP ET. Water, but not N level, has a highly significant effect on crop ET c. The study provides production functions relating cotton yield to ET c as well as soil water content at planting. These functions are useful for irrigation optimization and for forecasting the impact of water rationing and drought on regional water budgets and agricultural economies. The WP ET values obtained in this study compare well with those reported from the southwestern USA, Argentina and other developed cotton producing regions. Most importantly, these WP ET values are double the current values in Syria, suggesting that improved irrigation water and system management can improve WP ET, and thus enhance conservation and sustainability in this water-scarce region.
  • 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:
    • Stoffella, P. J.
    • He, Z. L.
    • Pereira, B. F. F.
    • Melfi, A. J.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 12
  • Year: 2011
  • Summary: The effects of irrigation with reclaimed wastewater (RWW) were compared with well water (WW) on citrus ( Citrus paradisi Macfad. * Citrus aurantium L.) nutrition. The deviation from the optimum percentage (DOP) index of macro- and micro-nutrients were used to evaluate the nutritional status: optimal (DOP=0), deficiency (DOP0). After 11 years of RWW irrigation the influence on nutrient concentration in plants decreased in the order: B > Zn > Mn=Ca > Cu > Mg > P > K. Reclaimed wastewater irritation positively affected citrus nutrition as it rendered the concentration of macro-nutrients, i.e. P, Ca, and K. closer to their optimum levels (SigmaDOP macro=7). However micro-nutrients tended to be excessive in plants (SigmaDOP micro=753) due to imbalanced supply of these elements in the RWW, particularly, for B and Cu. Citrus groves with long-term RWW irrigation may exercised caution in monitoring concentrations of B and Cu to avoid plant toxicity and soil quality degradation.
  • 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:
    • Alonso, J. C.
    • Magana, M.
    • Garcia de Leon, D.
    • Bravo, C.
    • Ponce, C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 1/2
  • Year: 2011
  • Summary: Organic farming is considered an important way to preserve biodiversity in agricultural landscapes. However, more work is still necessary to enable a full appraisal of the potential benefits of this way of farming, since studies differ in the evaluation of its effectiveness. Studies are particularly scarce in the Mediterranean region, where different climatic and ecological conditions prevent simple extrapolations from work carried out at northern latitudes. In the present study, an analysis of weed and arthropod communities was conducted in 28 pairs of organic and conventional fields in a dry cereal farmland in central Spain. Plants were identified to the species level, and arthropods to the family level. Pitfalls and sweep nets were used to sample respectively, ground-dwelling and plant-visiting arthropods. Abundance (total numbers of individuals), richness (total numbers of plant species or arthropod families), diversity (Shannon-Wiener index) and biomass (milligrams per pitfall/sweep-net) were calculated for each field and compared between organic and conventional fields using Generalized Linear Mixed Models (GLMMs). To explore the effect of predictor variables on weed richness and arthropod biomass, GLMMs were used. Organic fields showed higher abundance of weeds and arthropods (3.01 and 1.43 times, respectively), higher weed richness and diversity (2.76 and 2.33 times, respectively), and a 24% reduction in cereal plants. Arthropod diversity was lower in organic fields due to the presence of three dominant groups: Collembola, Chloropidae (Diptera), and Aphididae (Hemiptera). Weed richness increased as cereal cover decreased in organic fields. Total arthropod biomass was slightly higher in organic fields, and was affected by weed abundance and diversity. The differences between organic and conventional fields found in this study were higher than those reported for northern latitudes. This could be explained by the richer weed flora in the Mediterranean region, and a higher weed seed availability favored by the two-year rotation system typical of Iberian dry cereal farmland. We conclude that organic farming may contribute to preserve biodiversity in dryland cereal agroecosystems in the Mediterranean region.
  • Authors:
    • Nalley, L. L.
    • Popp, M.
  • Source: Journal of Agricultural and Applied Economics
  • Volume: 43
  • Issue: 3
  • Year: 2011
  • Summary: Arkansas cropping pattern changes at the county level were estimated under various scenarios involving a likely decline in water availability, the development of a biomass market for renewable energy production, and the potential of a widely used carbon offset market. These scenarios are analyzed separately and jointly to determine which of the three scenarios is expected to have the largest impact on net (emissions - sequestration) greenhouse gas (GHG) emissions, renewable fuels feedstock supply, and producer net returns. Land use choices included conventional crops of rice, cotton, soybean, corn, grain sorghum, pasture, and hay. Specialty crops of loblolly pine and switchgrass were modeled for their respective potential to sequester carbon and provide feedstock for renewable fuels. GHG emissions were measured across an array of production methods for each crop. Soil and lumber carbon sequestration was based on yield, soil texture, and tillage. Using the concept of additionality in which net GHG emissions reductions compared with a baseline level were rewarded at a carbon price of $15 per ton along with $40 per dry ton of switchgrass, baled at field side, revealed that irrigation restrictions had the largest negative impact on producer net returns while also lowering net GHG emissions. Introducing the higher carbon price led to minor positive income ramifications and greatly reduced net GHG emissions. Biomass production returns were higher than the returns from the carbon offset market, however, at the cost of greater net GHG emissions. The combination of all factors led to a significant increase in switchgrass and pine production. In this scenario, approximately 16% of the total income losses with lower nonirrigated yields were offset with returns from biomass and carbon markets. Lowest statewide net GHG emissions were achieved given least irrigation fuel use and a greater than 15% increase in carbon sequestration with pine and switchgrass.
  • Authors:
    • Levy, Y.
    • Raveh, E.
  • Source: Israel Journal of Plant Sciences
  • Volume: 59
  • Issue: 2/4
  • Year: 2011
  • Summary: During the last 50 years world irrigation has doubled while water withdrawal has tripled, leading to a global water crisis. As a result, growers around the world are forced to utilize effluent water for irrigation. In Israel the main source for such water is "SHAFDAN", i.e., tertiary-treated waste water, which is characterized by high chloride content that might increase in the future. These days about 33% of Israeli citrus orchards are irrigated with this water, yet its potential effect on citrus orchards is not clear. Citrus is one of the major fruit crops of the world and is relatively salt-sensitive. Recently it was reported that continuous application of KNO 3 might reduce chloride (Cl) uptake, and thus overcome the toxic effects of salinity. We examined the effect of KNO 3 fertilization and rootstock on grapefruit's response to salinized SHAFDAN reclaimed water over four years. Trees were grafted on five different rootstocks and fertigated with two KNO 3 regimes (118 vs. 148 mg 1 -1 NO 3), and exposed to five levels of salinized reclaimed water (from 221 to 765 mg 1 -1 Cl). During the experiment, soil electrical conductivity (EC) ranged from 2 dS m -1 (above the threshold for yield reduction) to 5 dS m -1. Leaf Cl (with the exception of trees grafted on Troyer) usually kept below toxicity level, i.e., >0.4%. Cumulative yield reduction due to salinity was 37.6, 21.3, 18.2, 17.2, and 12.6 kg per tree per dS m -1 of soil paste extract, for trees grafted on 812, SO, Volk, Gau, and Troy rootstocks, respectively, reflecting their sensitivity to the osmotic component of salt stress. Enhanced application of KNO 3 did not overcome the osmotic effect of salinity. These results indicate that while using reclaimed water, the osmotic component of salinity can be of higher significance than its toxic component, and more attention should be given in the future to the rootstock/scion combination's sensitivity to the osmotic component of salinity.
  • Authors:
    • Kawamura, O.
    • Mallmann, C.
    • Itano, E.
    • Ono, E.
    • Takabayashi, C.
    • Santos, J.
    • Hirooka, E.
  • Source: Food Additives and Contaminants Part A-Chemistry Analysis Control Exposure & Risk Assessment
  • Volume: 28
  • Issue: 8
  • Year: 2011
  • Summary: An indirect competitive enzyme-linked immunosorbent assay (ELISA) method using a monoclonal antibody for deoxynivalenol (DON) detection in wheat and flour was standardised and validated (detection limit - 177.1 g kg -1) and its performance was compared with LC-MS, (quantification limit=140 g kg -1). DON recovery ranged from 88.7% to 122.6% for wheat grain and from 70.6% to 139.3% for flour. Among the 38 wheat samples evaluated, DON was detected in 29 samples (76.3%) by ic-ELISA (281.6-12 291.4 g kg -1) and in 22 samples (57.9%) by LC-MS (155.3-9906.9 g kg -1). The 0.93 correlation coefficient between ic-ELISA and LC-MS data in 19 positive DON wheat samples demonstrated the reliability and efficiency of ic-ELISA. Results indicated that standardised ic-ELISA was suitable for DON screening in wheat samples and the need for continuous monitoring of mycotoxin levels in foodstuffs.
  • Authors:
    • Provance-Bowley, M.
    • Wyenandt, C. A.
    • Heckman, J. R.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 6
  • Year: 2011
  • Summary: When municipal shade tree leaves (MCST-leaf) are used as mulch the residues impact soil fertility for crops in the rotation. Pumpkin (Cucurbita pepo L.), grown near Pittstown, New Jersey, using leaf mulch, was followed in the next year by sweet corn (Zea mays L.) and by a fall-seeded rye (Secale cereale L.) cover crop. A 15 cm layer of MCST-leaf mulch adds an estimated 448 kg ha(-1) of N organically bound within 45 Mg ha(-1) of leaf dry matter. Because of the high C/N ratio, little of this N becomes available in the first growing season as was apparent from the N immobilization and N deficiency temporarily observed when the land was initially cropped to pumpkin. Sweet corn ear size was increased on amended soil compared to unamended soil. Crop responses with both sweet corn and rye indicated that significant amounts of nitrogen became plant available from leaf mulch decomposition. Leaf mulch improves soil fertility for several years after incorporation but in ways not apparent through soil nitrate testing. Besides enhanced N nutrition, sweet corn ear size on MCST-leaf amended soil may be related to other improvements in soil quality such as increased water holding capacity.