• Authors:
    • Norris, B.
    • Harkins, H.
    • Burmester, C.
    • Santen, E.
    • Curtis, L.
    • Dougherty, M.
    • Fulton, J.
    • AbdelGadir, A.
  • Source: Crop Management
  • Issue: August
  • Year: 2011
  • Summary: Fluctuations in dryland cotton yield in the Tennessee Valley region of northern Alabama are common and are usually related to irregular drought periods during the growing season. Subsurface drip irrigation (SDI) has gained popularity as a water delivery system for small, irregular-shaped cotton fields. A seven-year study was conducted with the objective to determine the response of seed cotton yield to SDI tape orientation relative to crop row direction and different irrigation rates under dryland conditions of the Tennessee Valley. Seven treatments were tested in a randomized incomplete block design which consisted of three irrigation treatments (33%, 66%, and 99% pan evaporation), two SDI tape orientations (parallel and perpendicular), and a dryland control. All SDI treatments produced yields significantly higher than non-irrigated, dryland cotton in four out of seven years. Maximum yield was obtained at a median pan evaporation water replacement value of 74%. No statistical differences were observed between SDI tape orientations on seed cotton yield in all years except in 1999 when parallel out yielded perpendicular at lower irrigation rates. Results confirm the long-term efficacy of supplemental irrigation to increase seed cotton yield irrespective of SDI tape placement during sporadic periods of drought. These results are applicable only for fields with the same soil type or with similar water movement characteristics.
  • Authors:
    • Primo-Millo, E.
    • Legaz, F.
    • Forner-Giner, M. A.
    • Forner, J.
  • Source: Journal of Plant Nutrition
  • Volume: 34
  • Issue: 10
  • Year: 2011
  • Summary: This study assesses the nutritional behavior of the new citrus rootstocks Forner-Alcaide no. 5 (FA-5) and Forner-Alcaide no. 13 (FA-13) under saline conditions compared to that of their parents, Cleopatra mandarin (CM) and Poncirus trifoliata (PT). Eighteen month-old plants grafted with Valencia orange scions were used in the experiment. The plants were grown in a greenhouse and irrigated over an eight-week period with nutrient solutions to which different amounts of sodium chloride (NaCl) had been added, namely 0, 20, 40 and 60 mM. Relative growth and the uptake of major mineral elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] were then determined. It was noted that the reduction in relative growth caused by salt treatment was greater in plants grafted on PT than those on FA-13, FA-5 and CM. Increasing the salt level in the growth medium reduced the absorption of the above mineral elements in all scion-rootstock combinations. However, this decrease was generally more marked in plants grafted on PT than in those on CM and FA-5. Plants on FA-13 showed an intermediate behavior. Positive correlations were found between growth and mineral element uptake by salt treated plants. Nutrient uptake was also plotted against chloride (Cl) and sodium (Na) concentrations in leaves and roots at increasing salt levels. This showed that N absorption was closely correlated (inversely) with Cl content in leaves, whereas K, Ca and Mg uptakes were correlated (inversely) with Na concentration in roots. This suggests that the accumulation of saline ions impacts growth and nutrient uptake by citrus plants.
  • Authors:
    • Nagler, P. L.
    • Hunsaker, D. J.
    • Neale, C. M. U.
    • Glenn, E. P.
  • Source: Hydrological Processes
  • Volume: 25
  • Issue: 26
  • Year: 2011
  • Summary: Crop coefficients were developed to determine crop water needs based on the evapotranspiration (ET) of a reference crop under a given set of meteorological conditions. Starting in the 1980s, crop coefficients developed through lysimeter studies or set by expert opinion began to be supplemented by remotely sensed vegetation indices (VI) that measured the actual status of the crop on a field-by-field basis. VIs measure the density of green foliage based on the reflectance of visible and near infrared (NIR) light from the canopy, and are highly correlated with plant physiological processes that depend on light absorption by a canopy such as ET and photosynthesis. Reflectance-based crop coefficients have now been developed for numerous individual crops, including corn, wheat, alfalfa, cotton, potato, sugar beet, vegetables, grapes and orchard crops. Other research has shown that VIs can be used to predict ET over fields of mixed crops, allowing them to be used to monitor ET over entire irrigation districts. VI-based crop coefficients can help reduce agricultural water use by matching irrigation rates to the actual water needs of a crop as it grows instead of to a modeled crop growing under optimal conditions. Recently, the concept has been applied to natural ecosystems at the local, regional and continental scales of measurement, using time-series satellite data from the MODIS sensors on the Terra satellite. VIs or other visible-NIR band algorithms are combined with meteorological data to predict ET in numerous biome types, from deserts, to arctic tundra, to tropical rainforests. These methods often closely match ET measured on the ground at the global FluxNet array of eddy covariance moisture and carbon flux towers. The primary advantage of VI methods for estimating ET is that transpiration is closely related to radiation absorbed by the plant canopy, which is closely related to VIs. The primary disadvantage is that they cannot capture stress effects or soil evaporation. Copyright (C) 2011 John Wiley & Sons, Ltd.
  • Authors:
    • Leib, B. G.
    • Gwathmey, C. O.
    • Main, C. L.
  • Source: Journal of Cotton Science
  • Volume: 15
  • Issue: 1
  • Year: 2011
  • Summary: Cotton ( Gossypium hirsutum L.) responses to supplemental irrigation need to be reassessed in humid, short-season environments. We conducted a 4-year study on a Typic Hapludalf at Jackson TN, to measure yield and maturity responses of contemporary cultivars to supplemental irrigation; to describe boll retention and distribution patterns associated with maturity responses; and to estimate the percentage of years in which yields may respond to irrigation. Treatments consisted of three rates of supplemental drip irrigation (nominally 3.81, 2.54, and 1.27 cm wk -1, adjusted for rainfall and prior irrigation), plus a non-irrigated check. Irrigation increased lint yields significantly in 3 of 4 years, with quadratic rate responses. The average yield increase was 38% at the 2.54-cm wk -1 rate. Yields were maximized with 35 to 37 cm of total water (irrigation+rainfall) between 40 and 120 days after planting. Yields were limited more by the accumulation of heat units than water supply in 2009. Irrigation delayed crop maturity by an average of 0.56 days for every additional cm water from irrigation or rainfall. Full irrigation expanded the effective fruiting zone on the plant from about 6.6 to 8.5 sympodial branches, increasing first position boll retention, but it delayed crop maturity mainly by shifting the location of the highest harvestable boll. Response to water supply showed that a yield response to irrigation could be expected in years with
  • Authors:
    • Arpaia, M. L.
    • Sanden, B.
    • Kallsen, C. E.
  • Source: HortScience
  • Volume: 46
  • Issue: 8
  • Year: 2011
  • Summary: The objective of this study was to measure effects of late-season water stress on fruit yield, size, quality, and color of an early-maturing navel orange cultivar, Citrus sinensis (L.) Osbeck 'Beck-Earli'. Three irrigation regimes were initiated in August in the southern San Joaquin Valley of California in 2006, 2007, and 2008. Increasing levels of water stress resulted in decreasing midday shaded leaf water potential (SLWP) ranging from -1.4 MPa in early September to a minimum of -2.5 MPa at harvest. Generally, over the course of the 3 years, late-season water stress decreased fruit grade and increased soluble solids concentration (SSC), titratable acidity (TA), the BrimA index, and orange color. Fruit juiciness and SSC:TA ratios were unaffected by late-season water stress. The intensity of the water stress in 2007 decreased fruit yield by number and weight and decreased the percentage of large fruit. When trees exposed to 2 years of late-season water stress were fully irrigated the next year, fruit yield and quality were similar to trees that had not experienced late-season water stress for the 3 years of the study.
  • Authors:
    • Schubert, A. M.
    • Hudnall, W. H.
    • Booker, J. D.
    • Bronson, K. F.
    • Malapati, A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 5
  • Year: 2011
  • Summary: Sulfate (SO 4) is one of the most important anions in soils and groundwater in semiarid regions, including west Texas. Crops' sulfur (S) requirement is about 10% to 20% of the nitrogen requirements. However, there is far less information on soil test SO 4-S (S in the SO 4 form [sulfate-S]) for the western United States, compared to the humid eastern United States. The deposition of S from the atmosphere has declined nationwide, as coal-fired power plants have been scrubbing their emissions of S. This, combined with greater cotton yields and the lack of S fertilization on the Texas Southern High Plains (SHP) point to the need for a soil profile SO 4-S assessment. The first objective of this study was to assess residual soil profile SO 4-S content in irrigated cotton ( Gossypium hirsutum) fields across a range of soil types and counties of the Texas SHP. The second objective was to compile regional SO 4-S concentration data from the Texas Water Development Board irrigation well water quality database and analyze Ogallala groundwater SO 4-S levels by county, soil map unit, and well depth. Soil profile (0 to 0.9 m [0 to 36 in]) SO 4-S content ranged from 120 to 475 kg ha -1 (107 to 424 lb ac -1) among seven center-pivot fields sampled. About half of this S was in the 0.6 to 0.9 m (24 to 36 in) soil layer, which typically was sandy clay loam or clay loam in texture. Well water SO 4-S concentration ranged from 9 to 220 mg L -1 (ppm) in clayey soils with deep groundwater to sandy soils with shallow groundwater, respectively. Groundwater SO 4-S concentration was greater than the USEPA drinking water standard of 83 mg L -1 in 32% of the wells, especially in the southeastern corner of the study area. There was no consistent relationship between soil map unit and SO 4-S content in the soil profile (0 to 0.9 m). A significant negative relationship between well depth and well water SO 4-S concentration was observed in all the eleven-county study area of the SHP of West Texas. In conclusion, soil profile SO 4 content to 0.9 m is high in SHP irrigated cotton fields and in most cases should be adequate for crop S nutritional requirements.
  • Authors:
    • Shukla, S.
    • Harris, W. G.
    • Obreza,T. A.
    • Sartain, J. B.
    • Schumann, A. W.
    • Mann, K. K.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 174
  • Issue: 6
  • Year: 2011
  • Summary: Variability in soil properties is a complication for fertilization, irrigation, and amendment application. However, only limited progress has been made in managing soil variability for uniform productivity and increased water-use efficiency. This study was designed to ameliorate the poor-productivity areas of the variable sandy soils in Florida citrus groves by using frequent small irrigations and applying organic and inorganic soil amendments. Two greenhouse experiments were set up with sorghum and radish as bioassay crops in a randomized complete block design (RCBD). The factors studied were two soil-productivity classes (very poor and very good), two water contents (50% and 100% of field capacity), two amendments (phosphatic clay and Fe humate), and two amendment rates (10 and 25 g kg -1 for sorghum and 50 and 100 g kg -1 for radish). Amendments applied at 50 and 100 g kg -1 increased the water-holding capacity (WHC) of poor soil by 2- to 6-fold, respectively. The lower rates (10 and 25 g kg -1) of amendments were not effective in enhancing sorghum growth. The higher rates (50 and 100 g kg -1) doubled the radish growth as compared to the control. The results indicate that rates greater than 50 g kg -1 of both amendments were effective in improving water retention and increasing productivity. Irrigation treatment of 100% of field capacity (FC) increased the sorghum and radish growth by about 2-fold as compared with the 50%-water content treatment. The results suggest that the root-zone water content should be maintained near FC by frequent small irrigations to enhance water availability in excessively drained sandy soils. In addition, application of soil amendments in the root zone can enhance the water retention of these soils. Furthermore, managing variable sandy soils with WHC-based irrigation can increase water uptake and crop production in the poor areas of the grove.
  • Authors:
    • Syvertsen, J. P.
    • Dunlop, J. M.
    • Melgar, J. C.
  • Source: HortScience
  • Volume: 46
  • Issue: 3
  • Year: 2011
  • Summary: Oleocellosis or oil spotting on the peel of citrus fruit is a common post-harvest injury caused by improper handling. Mechanical injury allows phytotoxic oil to leak out of oil glands and cause injury to surrounding flavedo cells, resulting in oleocellosis. Mechanical harvesting (MH) of 'Valencia' sweet orange is conducted in late spring, when the next season's fruitlets are in their early stages of development. There is a concern that mechanical injury from harvesting machines can cause oleocellosis and fruit drop of young, green 'Valencia' sweet orange fruitlets, especially late in the harvest season when fruitlets are relatively large. We evaluated the effects of winter drought stress and subsequent late-season MH with a canopy shaker on oleocellosis of 'Valencia' sweet orange fruitlets. In April, mature fruit size, juice content, total soluble solids, and acidity were unaffected by previous winter drought stress treatments. Mechanical harvesting removed ~90% to 95% of mature fruit and 20% to 50% of fruitlets depending on previous drought stress treatments and harvesting date. Beginning 1 week after the late harvest (13 June), attached fruitlets were tagged and visually evaluated approximately every other month to determine oleocellosis injury until the late-season harvest 12 months later. Only 12% of the fruitlets had oleocellosis on more than 30% of their surface area. Up to 75% of the fruitlets from the previously drought-stressed trees had less than 10% of their surface area injured after MH and 11% of these fruitlets dropped before harvest. Nonetheless, there was no significant increase in fruit drop with increased surface area injured nor was juice quality affected at harvest. Overall, fruit surface oleocellosis decreased and healed as fruit expanded, but surface blemishes did not completely disappear. Thus, fruitlet oleocellosis in late-season mechanically harvested trees was cosmetic and did not increase fruit drop nor alter internal fruit quality.
  • Authors:
    • Abreu, S. L.
    • Godsey, C. B.
    • Edwards, J. T.
    • Warren, J. G.
  • Source: Soil & Tillage Research
  • Volume: 117
  • Year: 2011
  • Summary: Intensive tillage during the last century has greatly reduced organic carbon contents of Oklahoma cropland. Increased public interest in carbon sequestration and the potential for carbon storage in no-till soils to offset CO2 emissions has brought about the need for accurate estimates of carbon sequestration in Oklahoma. Eight locations across Oklahoma were soil sampled to determine the impact of no-till farming practices on soil carbon storage. Locations consisted of side by side no-till and tilled fields sampled at four sites in each field. Samples were divided into 0–10, 10–20, 20–40, 40–70, and 70–110 cm depths and analyzed for organic carbon (OC) and total nitrogen (TN). Averaged across locations and depth, the concentration of organic carbon (OC) was 0.7 g kg−1 greater in no-till compared to tilled fields. As expected, differences between no-till and conventional till were dependent on length of time in no-till and annual precipitation. The greater the time in no-till management and the higher the annual precipitation, the greater the carbon stocks compared to conventional till fields. Despite the high degree of variation among sample locations, the mass of OC was significantly (p = 0.07), greater in the NT compared to that found in the CT fields, with the average difference being 8.6 Mg ha−1. The highest OC accumulation was observed in Miami with an average of 3.5 Mg ha−1 year−1, while at Lahoma 2 and Goodwell no accumulation of OC was observed. Eliminating tillage operations can increase OC accumulation with the presence of adequate rainfall and an extended period of time.
  • Authors:
    • Booker, J.
    • Lascano, R.
    • Acosta-Martinez, V.
    • Calderon, F.
    • Zobeck, T.
    • Upchurch, D.
  • Source: Biology and Fertility of Soils
  • Volume: 47
  • Issue: 6
  • Year: 2011
  • Summary: In dryland agriculture in semiarid regions, crop establishment is not always possible because precipitation may not be sufficient. Modification of soil properties can improve the soil quality and functioning including soil water capture and storage capacity for crop production in dryland conditions. ARS scientists established a study near Lubbock, Texas in 2003 to compare the soil properties under different dryland cropping systems and tillage management. After only 3 years, this study detected increases in soil microbial community size and enzyme activities important for nutrient cycling under rotations with a winter cover crop such as cotton-rye-sorghum and haygrazer-rye compared to continuous cotton or sorghum-cotton at 0-10 cm soil depth. After 5 years, higher soil total C was found under Hay-Rye compared to the other systems. In addition, microbial properties were already impacted in all alternative systems (haygrazer-rye, cotton-rye-sorghum and cotton-sorghum) studied compared to continuous cotton. Several microbial properties indicative of increased soil water availability were also higher under the alternative rotations to continuous cotton. However, continuation of this study is vitally important for the long-term evaluation and confirmation of these trends, and their implications in water management, soil quality and crop productivity in dryland.