• Authors:
    • Moore, A.
    • Ren, H.
    • Alva, A.
  • Source: American Journal of Plant Sciences
  • Volume: 3
  • Issue: 1
  • Year: 2012
  • Summary: Biomass accumulation and partitioning into different plant parts is a dynamic process during the plant growing period, which is influenced by crop management and climate factors. Adequate knowledge of biomass partitioning is important to manage the crops to gain maximum partitioning of assimilates into plant parts of economic significance, i.e. tubers in potato. This study was conducted using two potato cultivars grown in a sandy soil with center pivot irrigation under full irrigation (FI; irrigation to replenish 100% of water loss by evapotranspiration [ET]) and deficit irrigation (DI; replenish only 80% ET) and two nitrogen(N) rates (pre-plant + in-seasonN rates of 56+112 or 168+336 kg/ha). Plant samples were taken on 22, 44, 66, and 98 days after seedling emergence (DAE). With high N rate, tuber biomass of 'Umatilla Russet' cultivar in relation to total plant biomass varied from 23%-88% and 25%-86% over 22 to 98 DAE for the FIand DI treatments, respectively. The corresponding partitioning ranges were 30%-93% and 38%-93% at the low N rate. With respect to the'Ranger Russet' cultivar, biomass partitioning to tubers ranged from 36%-82% and 23%-84% for the FIand DI, respectively, at the high N rate, and 29%-87% and 39%-95% at the low N rate. Overall, this study demonstrated that within the range of N rate and irrigation treatments the biomass portioning into tubers was largely similar in both cultivars.
  • Authors:
    • Mustian, J.
    • Bordovsky, J.
  • Source: Applied Engineering in Agriculture
  • Volume: 28
  • Issue: 3
  • Year: 2012
  • Summary: The recent increase in the use of subsurface drip irrigation (SDI) for cotton production in the Texas High Plains has resulted in questions concerning drip lateral position and orientation relative to crop rows. Field experiments were conducted at Halfway, Texas to evaluate traditional SDI installations with crop rows spaced at 0.76 and 1.02 m; crop row to lateral offsets of 0.0, 0.13, 0.25, and 0.38 m; and crop rows perpendicularly crossing SDI laterals spaced at 0.76, 1.02, and 1.52 m. Traditionally installed SDI with cotton rows spaced at 0.76 m resulted in generally higher yield than those spaced at 1.02 in; however, differences were not significant over the 5-year period. Yields were significantly different between individual rows of adjacent row pairs irrigated with single SDI laterals when row offsets were greater than 0.25 m on 0.76-m row spacing. However, cotton plants from rows closest to the SDI lateral largely compensated for yield losses of rows farthest from the lateral. When considering perpendicularly crossing 1.52-m spaced laterals with 0.76-m wide crop rows, only modest declines in cotton lint yield (1.5% and 3.3%) occurred compared to traditional parallel row-lateral orientation with the same lateral and row spacing. With crop rows perpendicular to laterals, SDI lateral spacings resulted in average yields of 1802, 1869, and 1903 kg ha(-1) at distances of 1.52, 1.02, and 0.76 m, respectively. Orienting rows perpendicular to drip laterals using 0.76-m crop row widths resulted in significantly higher yields and irrigation water use efficiencies than 1.02-m row widths at high irrigation capacity. As water availability declines, these results will provide producers additional information on SDI installation and management.
  • Authors:
    • Burke, I.
    • Snyder, A.
    • Pittmann, D.
    • Gallagher, R.
    • Koenig, R.
    • Borrelli, K.
    • Hoagland, L.
    • Fuerst, E.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 4
  • Year: 2012
  • Summary: The nitrogen (N) dynamics of nine rotation systems designed to transition dryland cereal to organic production in eastern Washington State were examined. Systems combined cereal and legumes for grain, forage (FOR), and green manure (GRM). Few differences in N balances and soil inorganic N levels were found among transition systems when poor spring crop establishment resulted in competition from weeds. However, FOR and winter GRM crops produced adequate stands that were competitive with weeds and increased residual soil inorganic N in the final year of the transition. Winter legumes and continuous FOR systems demonstrated the greatest potential to provide a sustainable inorganic N source to subsequent organic cereal crops.
  • Authors:
    • Barnes, E.
    • Scharf, P.
    • Taylor, R.
    • Brown, C.
    • Wheeler, T.
    • Bronson, K.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 3
  • Year: 2012
  • Summary: Nitrogen is the main nutrient limiting irrigated cotton (Gossypium hirsutum L.) production in the southwestern United States. Canopy spectral reflectance may assess the need for in-season N in irrigated cotton and guide N fertilizer applications. However, calibration of remote sensing indices such as normalized difference vegetative index (NDVI) to the crop's need for N fertilizer is difficult. Well-fertilized reference strips or plots reference NDVI data in the crop area of interest but can result in rank growth and reduced lint yields. Recently, Oklahoma State University developed a calibration procedure of using multiple, sequential, N rate calibration plots, or a ramp approach for wheat (Triticum aestivum L) and corn (Zea mays L.). We tested this approach in irrigated cotton fields in Lubbock County, Texas, in 2008 and 2009. The main objective of this research was to test a calibration ramp approach to determining optimum in-season N fertilizer rates in irrigated cotton in West Texas. Near infrared, red, and amber reflectance was measured with active spectroradiometers at 1 m above the canopy. Wide ranges in soil type and irrigation amounts influenced NDVI much more than N fertilizer rate. Normalized difference vegetative index at mid-bloom and at peak bloom were positively related to N fertilizer rate in only one ramp in each year. These two ramp-years also had significant N fertilizer rate response in lint yield. Ramps that did not have mid- or peak bloom NDVI responses to N rate, likewise had no lint yield response to N rate. In both low irrigation- low N input and in high irrigation-high N input farms, in-season NDVI correctly predicted lint yield response to N fertilizer rate.
  • Authors:
    • Gitz, D.
    • Booker, J.
    • Bednarz, C.
    • Lascano, R.
    • Bufon, V.
  • Source: Irrigation Science
  • Volume: 30
  • Issue: 4
  • Year: 2012
  • Summary: Crop irrigation with subsurface drip (SDI) is increasing in the semiarid Texas High Plains (THP). Information on drip-tubing positioning, irrigation strategies, and wetted soil area is needed to increase rainwater effectiveness when well capacities are inadequate to meet full irrigation requirements. Time and resources necessary to test SDI strategies for different conditions through field experimentation is too large. However, a mechanistic model such as Hydrus-2D can quantify the effect of different installation geometries and irrigation strategies. Our objective was to experimentally validate the Hydrus-2D in an Amarillo soil in THP so that the model can be used to evaluate different irrigation frequency and timing strategies for SDI cotton. Results showed that Hydrus-2D simulated volumetric soil water content within +/- 3% of measured values, and simulation bias represented the smaller portion of the simulation error, indicating that the model can be used to evaluate irrigation strategies.
  • Authors:
    • Krutz, L.
    • Park, S.
    • Sij, J.
    • DeLaune, P.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 4
  • Year: 2012
  • Summary: Identifying management practices that conserve and protect water resources are very important to a wide variety of stakeholders within semiarid environments. The objective of this study was to develop water management strategies for transitioning tillage systems in cotton (Gossypium hirsutum L.) production within the Texas Rolling Plains when in a subsurface drip irrigation (SDI) system. Five irrigation regimes (0, 33, 66, 100, and 133% evapotranspiration [ET] replacement) and four tillage systems (conventional till, reduced till, no-till, and no-till with a terminated cover crop) were evaluated. The study was conducted for 3 yr and treatments were replicated three times in a randomized complete block design. Lint yields were not affected by the main effects of tillage or the interaction of tillage and ET replacement. In contrast ET replacement was a significant factor for lint yields, irrigation water use efficiency, and net returns. Greatest lint yields and net returns were achieved at 100% ET replacement. Fitted models indicated that optimum lint yields and net returns were achieved at 104.5% ET and 102% ET, respectively. Irrigation at 83% ET was within the 95% confidence interval for lint yield. Net returns were significantly higher for no-till systems compared with conventional till. Thus, adoption of conservation tillage systems should not negatively affect lint yield or net returns in deficit irrigated SDI cotton systems within the Texas Rolling Plains, particularly during the transition from intensively tilled systems to conservation tilled systems.
  • Authors:
    • Frisvold, G. B.
    • Konyar, K.
  • Source: Water Resources Research
  • Volume: 48
  • Issue: 5
  • Year: 2012
  • Summary: This study examined how agriculture in six southwestern states might adapt to large reductions in water supplies, using the U.S. Agricultural Resource Model (USARM), a multiregion, multicommodity agricultural sector model. In the simulation, irrigation water supplies were reduced 25% in five Southern Mountain (SM) states and by 5% in California. USARM results were compared to those from a "rationing" model, which assumes no input substitution or changes in water use intensity, relying on land fallowing as the only means of adapting to water scarcity. The rationing model also ignores changes in output prices. Results quantify the importance of economic adjustment mechanisms and changes in output prices. Under the rationing model, SM irrigators lose $65 in net income. Compared to this price exogenous, "land-fallowing only" response, allowing irrigators to change cropping patterns, practice deficit irrigation, and adjust use of other inputs reduced irrigator costs of water shortages to $22 million. Allowing irrigators to pass on price increases to purchasers reduced income losses further, to $15 million. Higher crop prices from reduced production imposed direct losses of $130 million on first purchasers of crops, which include livestock and dairy producers, and cotton gins. SM agriculture, as a whole, was resilient to the water supply shock, with production of high value specialty crops along the Lower Colorado River little affected. Particular crops were vulnerable however. Cotton production and net returns fell substantially, while reductions in water devoted to alfalfa accounted for 57% of regional water reduction.
  • Authors:
    • Hague, S.
    • Hequet, E.
    • Smith, W.
    • Ng, E. H.
    • Gregory, K.
  • Source: Crop Science
  • Volume: 52
  • Issue: 3
  • Year: 2012
  • Summary: The U.S. cotton (Gossypium spp.) industry has shifted focus in recent years to an export market, necessitating further development of upland cotton (G. hirsutum L.) cultivars with superior fiber properties to maintain competitiveness. This study was conducted to compare both fiber and yarn performance of upland cotton genotypes with similar average fiber length but enhanced fiber bundle strength (Str) with two high quality commercial controls, 'FM 832LL' and 'DP 491'. The high Str strains and commercial upland controls were grown in Weslaco, TX, during the summers of 2009 and 2010 with standard agronomic practices for south Texas, including furrow irrigation. Plots were spindle-machine harvested, seedcotton ginned on a research gin without a lint cleaner, and lint and yarn tested at the Fiber and Biopolymer Research Institute (FBRI) in Lubbock, TX. Lint and yarn data collected included high volume instrument (HVI) and advanced fiber information system (AFIS) derived data and ring spun yarn data (mini-spinning protocol). Years were different for almost every fiber and yarn property except Str, immature fiber content (IFC), yarn tenacity (Ten), work required for yarn breakage (Work to Break) and the number of thin places per kilometer that are at least 50% smaller in diameter than adjacent portions of yarn (Thin). All of the high Str strains had higher Ten in 2009 than the controls and 9 of the 11 had higher Ten in 2010. The high Str genotypes resulted in more even yarns (as determined with the Uster Tester 3 [Uster Technologies]).
  • Authors:
    • Wang, G.
    • Thorp, K. R.
    • Norton, R.
    • Gutierrez, M.
  • Source: Crop Science
  • Volume: 52
  • Issue: 2
  • Year: 2012
  • Summary: Canopy reflectance plays an increasingly important role in crop management and yield prediction at large scale. The relationship of four spectral reflectance indices with cotton (Gossypium hirsutum L.) biomass, leaf area index (LAI), and crop yield were investigated using three cotton varieties and five N rates in the irrigated low desert in Arizona during the 2009 and 2010 growing seasons. Biomass, LAI, and canopy reflectance indices (normalized difference vegetation index [NDVI], simple ratio [SR], near-infrared index [NIR] and ratio vegetation index [RVI]) were determined at different growth stages. The commonly used NDVI and the other three canopy reflectance indices explained over 87% variation in cotton biomass (all R-2 > 0.87) and LAI (R-2 > 0.93). Indices SR, NIR, and RVI all had higher coefficients of determination (R-2) compared to NDVI because these indices were not saturated at late growth stages. There was no significant relationship between lint yield and the spectral indices measured at early growth stages. However, the spectral indices determined at peak bloom showed significant correlations with lint yield. Indices SR, NIR, and RVI explained 56, 60, and 58% of variations in cotton lint yield, respectively, while NDVI only explained 47% of variation in lint yield. This study suggests canopy reflectance indices can be used to predict cotton lint yield at peak bloom and the accuracy of yield prediction can be significantly improved when SR, NIR, and RVI are used.
  • Authors:
    • Singh, M.
    • Jhala, A. J.
  • Source: Weed Technology
  • Volume: 26
  • Issue: 3
  • Year: 2012
  • Summary: Soil-applied herbicides are commonly used for broad-spectrum residual weed control in Florida citrus. Groundwater contamination from some soil-applied herbicides has been reported in citrus growing areas in Florida. Indaziflam is a new soil-applied herbicide recently registered for broad-spectrum weed control in Florida citrus. There is no information available on leaching behavior of indaziflam in sandy soil. Experiments were conducted to compare leaching of indaziflam with five commercially used residual herbicides in a Florida Candler soil under simulated rainfall of 5 or 15 cm ha -1. Herbicide movement down soil columns was measured by visually evaluating injury and harvesting aboveground biomass of the bioassay species annual ryegrass. Ryegrass was not injured and plant biomass was not affected beyond 30 cm when indaziflam at a recommended rate of 73 g ai ha -1 was leached through the soil column. Leaching of indaziflam increased with increasing amounts of rainfall. For example, indaziflam leached up to 12.20.8 cm (values are expressedSD) and 27.22.6 cm at 5 and 15 cm ha -1 rainfall, respectively. The herbicide ranking from high to low mobility at 15 cm ha -1 of rainfall was bromacil=norflurazon>indaziflam>simazine=pendimethalin>diuron. Overall results suggested that indaziflam leaching was limited in Florida Candler soil in this study; however, field experiments are required to confirm the leaching of indaziflam under natural rainfall situation.