• Authors:
    • Horwath, W. R.
    • Wroble, J. F.
    • Munk, D. S.
    • Wallender, W. W.
    • Singh, P. N.
    • Mitchell, J. P.
    • Hogan, P.
    • Roy, R.
    • Hanson, B. R.
  • Source: California Agriculture
  • Volume: 66
  • Issue: 2
  • Year: 2012
  • Summary: Reducing tillage and maintaining crop residues on the soil surface could improve the water use efficiency of California crop production. In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration demand of 30 inches, coupling no-tillage with practices preserving high residues could reduce summer soil evaporative losses by about 4 inches (13%). However, practical factors, including the need for different equipment and management approaches, will need to be considered before adopting these practices.
  • Authors:
    • Evett, S. R.
    • O'Shaughnessy, S. A.
    • Colaizzi, P. D.
    • Howell, T. A.
  • Source: Transactions of the American Society of Agricultural and Biological Engineers
  • Volume: 55
  • Issue: 2
  • Year: 2012
  • Summary: Studies using the time-temperature threshold (TTT) method for irrigation scheduling have been documented for cotton, corn, and soybean. However, there are limited studies of irrigation management of grain sorghum ( Sorghum bicolor, L.) with this plant-feedback system. In this two-year study, the TTT method was investigated as an automatic irrigation control algorithm for a late-maturing grain sorghum hybrid (Pioneer 84G62) grown in 2009 and an early maturing hybrid (Moench, NC+ 5C35) grown in 2010. The method was evaluated by comparing grain sorghum responses of biomass and dry grain yields, crop evapotranspiration (ET c), water use efficiency (WUE), and irrigation water use efficiency (IWUE) between automatic and manual control methods of irrigation scheduling at different deficit irrigation treatments (i.e., 80%, 55%, 30%, and 0% of full replenishment of soil water depletion to 1.5 m depth). Irrigation scheduling using the TTT method produced mean response variables of yield (biomass and grain), WUE, and IWUE that were similar or better than those from the manually scheduled method in both years. Water use efficiency was highest at the 80% and 55% levels in 2009 and 2010, respectively. Average IWUE was highest at the 55% level in 2009 and at the 30% level in 2010. For both of these responses, differences among irrigation treatment levels were not always significant. Crop production functions were curvilinear in both years as dry grain yields began to plateau between water application amounts delivered from irrigation treatments at the 55% and 80% levels. Results from this study indicate that both late and early maturing hybrids of grain sorghum are responsive to the TTT method of irrigation scheduling. Irrigation management with this algorithm can produce biomass and dry grain yields, ET c, WUE, and IWUE levels that are similar to those achieved with an accurate irrigation scheduling method based on direct soil water measurement.
  • Authors:
    • Roostaee, M.
    • Liaghat, A.
    • Parsinejad, M.
    • Tabrizi, M. S.
    • Nahvinia, M.
  • Source: International Journal of Agriculture: Research and Review
  • Volume: 2
  • Issue: 3
  • Year: 2012
  • Summary: Sustainable irrigated agriculture entails monitoring water, salt balance and effective depth of root zone. A lysimeter study was based absorption of plant water requirement beyond predefined root depth. Experiment was conducted with three treatments in three replications at the research field of the University of Tehran in Karaj, Iran, in 2007 on soybean including: treatment A at MAD (Maximum Allowable Depletion) of 55%, treatment B at MAD=65% and treatment C also at MAD=65% but with 30% excess irrigation. The results showed in treatment C crop yield not only did not significantly decrease as compared with treatment A but water application efficiency increased by 11.2%. Water extraction of plants at the deeper soil layers in response to longer irrigation intervals can result in increased plant water uptake efficiency.
  • Authors:
    • Teixeira Junior, T.
    • Colombo, G. A.
    • Afferri, F. S.
    • Cancellier, L. L.
    • Pires, L. P. M.
    • Peluzio, J. M.
    • Ribeiro, G. R. dos S.
  • Source: Ciência Rural
  • Volume: 42
  • Issue: 3
  • Year: 2012
  • Summary: In order to evaluate the genetic divergence among soybean cultivars, an assay was carried out at Formoso do Araguaia, TO, Brazil, in off-season of 2007, in irrigated lowland conditions. The experimental design were randomized blocks with 12 treatments and three replications. Genetic divergence was evaluated by multivariate procedures: Mahalanobis distance, Tocher clustering method's and nearest neighbor method. It was observed the formation of two distinct groups by the dendrogram of genetic dissimilarity, which were identical to those groups formed by Tocher's method. The Tocher optimization method and the nearest neighbor agreed among themselves. The traits number of days to maturity, plant height and weight of 100 seed were the ones that most contributed for genetic dissimilarity. The presence of genetic variability allowed the identification of dissimilar cultivars with high average for the evaluated traits. The hybridations 'DOKO' * 'CONQUEST' and 'DOKO' * 'FT-2000' are promising to obtain segregating populations with high variability.
  • Authors:
    • Gitelson, A. A.
    • Peng, Y.
  • Source: Remote Sensing of Environment
  • Volume: 117
  • Issue: 440–448
  • Year: 2012
  • Summary: The synoptic quantification of crop gross primary productivity (GPP) is essential for studying carbon budgets in croplands and monitoring crop status. In this study, we applied a recently developed model, which relates crop GPP to a product of total crop chlorophyll content and incoming photosynthetically active radiation, for the remote estimation of GPP in two crop types (maize and soybean) with contrasting canopy architectures and leaf structures. The objective of this study was to evaluate performances of twelve vegetation indices used for detecting different vegetation biophysical characteristics, in estimating GPP of rainfed and irrigated crops over a period from 2001 through 2008. Indices tested in the model exhibited strong and significant relationships with widely variable GPP in each crop (GPP ranged from 0 to 19 gC/m 2/d for soybean and 0 to 35 gC/m 2/d for maize), however, they were species-specific. Only three indices, which use MERIS red edge and NIR spectral bands (i.e. red edge chlorophyll index, MERIS Terrestrial Chlorophyll Index and red edge NDVI), were found to be able to estimate GPP accurately in both crops combined, with root mean square errors (RMSE) below 3.2 gC/m 2/d. It was also shown that two indices, red edge chlorophyll index and red edge NDVI with a red edge band around 720 nm, were non-species-specific and yielded a very accurate estimation of GPP in maize and soybean combined, with RMSEs below 2.9 gC/m 2/d and coefficients of variation below 21%.
  • Authors:
    • King, C. A.
    • Edwards, J. T.
    • Carter, T. E.
    • Purcell, L. C.
    • Ries, L. L.
  • Source: Crop Science
  • Volume: 52
  • Issue: 1
  • Year: 2012
  • Summary: Delayed wilting is observed in a few unusual soybean [ Glycine max (L.) Merr.] genotypes, but the reasons and importance of this trait for conferring agronomic drought tolerance are poorly understood. We hypothesized that soybean genotypes with delayed wilting conserve soil moisture by restricting transpiration and that this would be reflected in decreased radiation use efficiency (RUE) and/or improved water use efficiency (WUE). Water conserved when soil moisture was plentiful would be available later in the season when drought is usually more severe. Irrigated field experiments in eight environments compared RUE of genotypes known to wilt differently during drought. In addition, we measured stomatal conductance, carbon isotope discrimination (CID), volumetric soil-moisture content, stomatal density, and canopy temperature depression. In six of the eight environments, slow-wilting genotypes generally had lower RUE than fast-wilting genotypes, which is consistent with our hypothesis. Three of four slow-wilting genotypes had higher soil moisture immediately before irrigation than fast-wilting genotypes, which is also consistent with the hypothesis. Genotypic differences in CID (a proxy for WUE) were present but were not consistently related with slow wilting. No genotypic differences were detected in stomatal conductance or canopy temperature. These results suggest that multiple mechanisms involving RUE and WUE could result in soil-water conservation in these diverse genotypes.
  • Authors:
    • Isla, R.
    • Urrego, Y. F.
    • Salmeron, M.
    • Cavero, J.
  • Source: Agricultural Water Management
  • Volume: 113
  • Issue: October
  • Year: 2012
  • Summary: Typical field conditions under sprinkler irrigation include low irrigation uniformity and non-uniform plant density, which can affect the crop yield and the environmental impact of irrigation. The effect of the uniformity of sprinkler irrigation and plant density on the variability of maize grain yield under semi-arid conditions was evaluated, and the relevance of the spatial variability of these two variables on the simulation of maize grain yield was tested with the DSSAT-CERES-Maize model (V 4.5). Experimental field data from three maize growing seasons (2006, 2009 and 2010) with nighttime or daytime sprinkler irrigation were used to test the model performance. Yield, irrigation depths and plant density distribution were measured in 18 m * 18 m plots divided in 25 sub-plots. Regression analysis showed that the variability of plant density and seasonal irrigation depth (due to irrigation non-uniformity) was able to explain from 28 to 77% of the variability in maize grain yield for the experiments with a relatively high coefficient of uniformity (CU) (73-84%) and high plant density (more than 74,844 plants ha -1). Taking into account irrigation depth distribution improved maize yield simulations compared to simulations with the average irrigation water applied. The root mean square error ( RMSE) decreased from 637 to 328 kg ha -1. Maize yield was over-predicted by 3% when irrigation depth distribution was not considered. Including plant density distribution in the simulations did not improve maize yield simulations. The simulated decrease in maize yield with decreasing CU of irrigation from 100 to 70% varied from year to year and caused reductions in yield ranging from 0.75 to 2.5 Mg ha -1. The ability of the model to simulate CU effects on maize yield is shown.
  • Authors:
    • Skaggs, K. E.
    • Irmak, S.
  • Source: Journal of Irrigation and Drainage Engineering
  • Volume: 138
  • Issue: 2
  • Year: 2012
  • Summary: The use of Penman-Monteith (PM)-type combination-based energy-balance equations to estimate reference evapotranspiration (ET ref) requires climatic data measured over well-watered and well-maintained reference grass or alfalfa vegetation surfaces. However, establishing and maintaining reference weather stations for a long period of time is a very formidable and expensive process. Thus, expansion of the microclimate data available for use in the PM equation for estimating ET ref is needed. In the absence of reference weather stations, one alternative is using microclimatic data measured over other well-watered vegetation surfaces as inputs to the PM equation. This study determines if weather data collected from a well-watered soybean surface in a semihumid climate can be used for this purpose. Measured and estimated microclimate variables, including net radiation ( Rn ), average air temperature ( Tave), dew-point temperature ( Td ), average relative humidity (RH ave), aerodynamic resistance ( ra ), and wind speed at 3 m ( u3) of a soybean and a grass canopy in South Central Nebraska, were analyzed and compared. The aerodynamic resistances of the soybean and grass canopies showed the largest percent difference of any of the microclimate variables for both 2007 and 2008. Wind speed was the primary microclimate variable with the largest percent difference between the two fields. The average percent differences in u3 between the soybean and grass field were 9.0 and 9.8% for 2007 and 2008. Although Tave, RH ave, and Td percent differences were not that large, there were distinct seasonalities to the differences. Grass and alfalfa reference evapotranspiration (ET o and ET r, respectively) calculations using data from the soybean (ET o-s and ET r-s ) and grass (ET o-g and ET r-g ) canopies were compared daily and seasonally. Seasonal total ET o and ET r estimates using soybean and grass microclimate data were very close, and within 1 and 2% during 2007 (ET o-g =583 mm and ET o-s =576 mm; ET r-g =751 mm and ET r-s =733 mm), and 4 and 5% during 2008 (ET o-g =554 mm and ET o-s =531 mm; ET r-g =707 mm and ET r-s =669 mm). In 2007, differences in temperature variables were most correlated to differences in ETref estimates. In 2008, the greatest correlations of differences in ET o and ET r were with differences in Tave, RHave, and u3. The results indicated that the microclimate data measured over an irrigated soybean canopy during normal or wet years (rainfall ≥300 mm during the growing season) can be used in place of measurements taken over a grass canopy to estimate ET o and ET r in climatic conditions similar to semihumid climatic conditions of South Central Nebraska when reference weather station data are not available to solve the standardized PM equation.
  • Authors:
    • Kumar, V.
    • Ahalawat, I. P. S.
    • Kumar, U.
    • Vivek
  • Source: Advances in Plant Sciences
  • Volume: 25
  • Issue: 1
  • Year: 2012
  • Summary: A field experiment was conducted at Agricultural Research Farm, J.V. College Baraut, Baghpat (UP), during two consecutive seasons of Rabi, 2001-02 and 2002-03 to find out the yield potential as influenced by different row ratios (4:1 and 6:1) in lentil+mustard intercropping, Levels of irrigations (control, 0.2 and 0.4 IW/CPE) and doses of fertilizers (30 Kg N+40 Kg P 2O 5/ha and 60 Kg N+60 Kg P 2O 5/ha) were applied in the present study. Association of lentil with mustard under 4:1 row ratio was found more suitable as it accounted for higher value in terms of land equitant ratio (LER) and yield potential. Irrigation @ 0.4 IW/CPE resulted maximum seed yield in lentil (9.90 q/ha.) and mustard (13.30 q/ha), to achieve higher yield advantage and efficient source utilization, Seed yield of both the crops was significantly increased with increasing levels of fertilizers up to 60 KgN+60 Kg P 2O 5/ha.
  • Authors:
    • Ferguson, R.
    • Shapiro, C. A.
    • Wortmann, C. S.
    • Mainz, M.
  • Source: Crop Management
  • Issue: May
  • Year: 2012
  • Summary: High-yield soybean (Glycine max L.) has a high rate of N uptake during grain fill which may exceed N available from biological N fixation and mineralization of soil organic N. Other research findings show a low probability of response to N applied at early grain fill for yield 60 bu/acre yield are inconsistent. The effect of applying N and S to the soil at early podfill was determined in Nebraska by conducting 56 irrigated trials, including 44 with mean yield >60 bu/acre. Mean yield increases with 27 lb/acre N applied and >60 bu/acre yield were 2.5 bu/acre in south-central, 1.6 bu/acre in northeast, and not significant in southeast Nebraska. There was no added yield with applying 54 compared with 27 lb/acre N or with the addition of 4.5 lb/acre S. Variations in soil properties and in leaf N and S concentrations were not related to yield or the response to applied N. Depending on the grain to fertilizer price ratio, application of N at early pod fill may be profitable, especially if the cost of application is low such as through fertigation.