• Authors:
    • Carmo, C.
    • Lhamby, J.
    • Ambrosi, I.
    • Santos, H.
  • Source: Ciencia Rural
  • Volume: 34
  • Issue: 1
  • Year: 2004
  • Summary: Soil tillage and crop rotation and succession systems were assessed in Passo Fundo, Rio Grande do Sul, Brazil, from 1994/95 to 1997/98. Four soil tillage systems, i.e. no-tillage, minimum tillage, conventional tillage using a disc plough, and conventional tillage using a mouldboard plough, and three crop rotation and succession systems, i.e. system I (wheat/soyabean), system II (wheat/soyabean and common vetch [ Vicia sativa]/sorghum or maize) and system III (wheat/soyabean, common vetch/sorghum or maize, and white oats/soyabean), were compared. An experimental design of randomized blocks with split-plots and three replications was used. The main plot was formed by the soil tillage systems, while the split-plots consisted of the crop rotation and succession systems. Two types of analysis were applied to the net return of soil tillage and crop rotation and succession systems: mean-variance and risk analysis. By the mean-variance analysis, no-tillage and minimum tillage, which presented higher net returns, were the best alternatives to be offered to the farmer. By the stochastic dominance analysis, no-tillage and crop rotation with two winters without wheat showed the highest profit and the lowest risk.
  • Authors:
    • Mitchell, P. D.
    • Hurley, T. M.
    • Rice, M. E.
  • Source: American Journal of Agricultural Economics
  • Volume: 86
  • Issue: 2
  • Year: 2004
  • Summary: A conceptual model is developed to evaluate the effect of Bt maize on risk. The model is applied to the case of dryland maize in Boone County, Iowa and irrigated maize in Cuming County, Nebraska (USA). Results highlight the importance of distinguishing between marginal and aggregate risk effects and demonstrate that the effect of Bt maize on risk depends crucially on the price paid for the technology. Empirical results show that, depending on the price, Bt maize can be marginally risk increasing or decreasing and can either increase or decrease maize acreage. Also, depending on the price, Bt maize can provide a risk benefit to farmers, even when Bt maize is risk increasing.
  • Authors:
    • Mosier, A. R.
    • Burke, I. C.
    • Kaye, J. P.
    • Guerschman, J. P.
  • Source: Ecological Applications
  • Volume: 14
  • Issue: 4
  • Year: 2004
  • Summary: Land-use change is an important driver of soil-atmosphere gas exchange, but current greenhouse-gas budgets lack data from urban lands. Field comparisons of urban and non-urban ecosystems are required to predict the consequences of global urban-land expansion for greenhouse-gas budgets. In a rapidly urbanizing region of the U.S. Great Plains, we measured soil-atmosphere exchange of methane (CH 4) and nitrous oxide (N 2O) for one year in replicated ( n=3) urban lawn, native shortgrass steppe, dryland wheat-fallow, and flood-irrigated corn ecosystems. All soils were net sinks for atmospheric CH 4, but uptake by urban, corn, and wheat-fallow soils was half that of native grasslands (-0.300.04 g C.m -2.yr -1 [mean1 Se]). Urban (0.240.03 g N.m -2.yr -1) and corn (0.200.02 g N.m -2.yr -1) soils emitted 10 times more N 2O to the atmosphere than native grassland and wheat-fallow soils. Using remotely sensed land-cover data we calculated an upper bound for the contribution of lawns to regional soil-atmosphere gas fluxes. Urban lawns occupied 6.4% of a 1578-km 2 study region, but contribute up to 5% and 30% of the regional soil CH 4 consumption and N 2O emission, respectively, from land-use types that we sampled. Lawns that cover small portions of the landscape may contribute significantly to regional soil-atmosphere gas exchange.
  • Authors:
    • Kumpawat, B. S.
  • Source: Indian Journal of Agronomy
  • Volume: 49
  • Issue: 1
  • Year: 2004
  • Summary: A field experiment was carried out under irrigated condition on fixed site during 1986-2001 at Dryland Farming Research Station, Arjia, Bhilwara, Rajasthan, to find out the effect of integrated nutrient supply system in maize ( Zea mays L.)-Indian mustard [ Brassica juncea (L.) Czernj. & Cosson] cropping system. The highest mustard-equivalent yield (24.88 q/ha) was recorded with the application of 100% recommended N in the rainy season through FYM and 100% recommended NP in the winter season through inorganic fertilizers. Maximum net monetary returns (Rs 15,537/ha), benefit:cost ratio (2.07) and agronomic efficiency (16.1) were obtained from the treatment consisting of 50 and 100% recommended NP through fertilizers to maize and mustard respectively. Amount of available phosphorus increased over initial value when organic manures and crop residues were incorporated. Organic carbon status declined in the control, while there was build up in organic source-incorporated plots.
  • Authors:
    • Skinner, D. Z.
    • Liang, G. H.
  • Year: 2004
  • Summary: This book contains chapters on: genetic transformation; mechanisms of transgene locus formation; gene stacking through site-specific integration; transgenics of plant hormones and their potential application in horticultural crops; avidin in transgenic maize; genetic engineering protocols and use to enhance stress tolerance in wheat; development and utilization of transformation in Medicago spp.; sorghum transformation for resistance to fungal pathogens and drought; current progress and future prospects in rice transformation; successes and challenges in cotton transformation; progress in transforming the recalcitrant soyabean; progress in vegetable crop transformation and future prospects and challenges; genetic transformation of turfgrass; and risks associated with genetically engineered crops.
  • Authors:
    • Figueroa-Viramontes, R.
    • Vazquez-Vazquez, C.
    • Salazar-Sosa, E.
    • Lopez-Martinez, J. D.
    • Berumen-Padilla, S.
    • Martinez-Rubin, E.
  • Source: Agrofaz: publicación semestral de investigación científica, ISSN 1665-8892, Vol. 3, Nº. 1, 2003 or Phyton REVISTA INTERNACIONAL DE BOTÁNICA EXPERIMENTAL INTERNATIONAL JOURNAL OF EXPERIMENTAL BOTANY
  • Volume: 2004
  • Year: 2004
  • Summary: Taking into consideration that potential evapotranspiration normally exceeds the growing season rainfall and that a water shortage can occur unless a reserve of soil water is stored before the crop is planted, it can be concluded that the amount of stored soil water at sowing time is a critical factor in the success of dryland cropping systems. The main aim of this investigation was to know if interaction chi 2 test is a valuable tool, when taking into account stored soil (0-60 cm depth) water at sowing time and maize grain yield, in making decision for sowing or not sowing at a given time. Data on the amount of soil water at sowing time and maize grain yield from four experiments carried out during 2001 and 2002 at the Ejido Francisco Villa, Lerdo, Durango, Mexico were used to run the interaction chi 2 tests. For a minimum maize yield of 1000 kg ha -1, the following level of stored soil water was defined as critical: 8.34 cm for cv. 'Blanco Hualauises' and cv. 'H-412'. The interaction chi 2 test is a good tool to determine soil water critical levels at the sowing time of maize to ensure success in the present dryland cropping system.
  • Authors:
    • Zamfir, M. C.
    • Mitu, D.
  • Source: Analele ale Institutului de Cercetări pentru Cereale şi Plante Tehnice Fundulea
  • Volume: 71
  • Year: 2004
  • Summary: In 2001-03 at ARDS Teleorman, Romania, 14 maize hybrids were studied for their response to drought during the first part (2002) and second part (2001) of summer, and to prolonged drought (2003) under irrigated and dryland conditions. Paltin, Campion, Rapsodia, Danubiu, Faur and Olt performed well under irrigated and dryland conditions. Partizan, Orizont, Vultur, Octavian and Granit were sensitive to drought. During the dry years, the disparity in flowering (days) and the frequency of sterile plants resulted in a significant reduction in kernel yield. Prolonged drought throughout the growth period resulted in higher yield losses (76-77%) compared with partial drought experienced in the second part of summer (62-65%) or in the first part of maize growth (26-30%).
  • Authors:
    • Reddy, G. B.
    • Brock, B.
    • Naderman, G.
    • Raczkowski, C. W.
  • Source: Proceedings of the 26th Southern Conservation Tillage Conference for Sustainable Agriculture 8-9 June, 2004, Raleigh, North Carolina
  • Year: 2004
  • Summary: This study reports the results of sampling soil within a field experiment at CEFS, the Cherry Farm, Goldsboro, North Carolina. The experiment tested effects of six years of conservation tillage with cover crops, contrasted with chisel plow/disk tillage without cover crops, under three crop rotations. In April, 2003 two sets of undisturbed core samples were collected from six mapped soil areas, at depth increments of 0-2 and 2-5 inches, replicated four times. One set was used for soil bulk density; the other provided soil carbon and total nitrogen contents. The study found strong and consistent inverse correlations between soil carbon content and bulk density. Under conservation tillage the surface two inches generally sustained suitable density for root activities. However, at 2-5 inches density approached or exceeded 1.6 g cm-3. Given the textures involved, this density likely would affect root growth, especially under non-ideal, wet/cool or dry/hard conditions. This would be especially important for crop establishment within this prime rooting zone. This low carbon/high-density problem was less likely for soils containing the influences of more silt with less sand. It was greater when corn, peanut and cotton were grown compared to producing soyabean or wheat/soybean with corn. This study revealed increased carbon sequestration from the conservation tillage systems used, along with increased total N content in the surface five inches of soil. Conservation tillage as practiced helped to reduce the "greenhouse effect" and lessened N leaching losses, holding more of these elements within the topsoil.
  • Authors:
    • Raducu, I.
  • Source: Analele Institutului de Cercetari pentru Cereale si Plante Tehnice, Fundulea
  • Volume: 71
  • Year: 2004
  • Summary: At Teleorman, Romania, during 2002-2003, the flowering biology of 17 inbred lines, which were the parental forms of 11 Romanian maize hybrids (Milcov, Paltin, Campion, Faur, Fulger, Partizan, Neptun, Panciu, Ileana, Star and Premier), under varying conditions (as a result of irrigation and sowing date treatments) was studied. The genotype * environment interaction had significant effects on the flowering biology of the genotypes. Under the ecological conditions of Draganesti-Vlasca, Lc-574, Lc-553 and Lc-607 lines exhibited stability in stigma appearance, while Lc-403, Lc-686 and Lc-607 lines proved to be more stable in tassel flowering dynamics. The parental forms of single crosses Faur, Campion and Neptun showed good stability and adaptability. The parental forms of single crosses Campion and Neptun showed satisfactory performance under normal conditions (irrigation), but exhibited significant disparities in flowering under dryland conditions. The parental forms of single cross Fulger showed good adaptability (reduced disparity at flowering) under dryland conditions but exhibited large disparities under irrigated conditions. The parental forms of single cross Star have manifested constant disparities in flowering under almost all experimental conditions.
  • Authors:
    • Johnson, J. J.
    • Doerge, T. A.
    • Shanahan, J. F.
    • Vigil, M. F.
  • Source: Precision Agriculture
  • Volume: 5
  • Issue: 3
  • Year: 2004
  • Summary: The goal of this research was to determine the potential for use of site-specific management of corn hybrids and plant densities in dryland landscapes of the Great Plains by determining (1) within-field yield variation, (2) yield response of different hybrids and plant densities to variability, and (3) landscape attributes associated with yield variation. This work was conducted on three adjacent fields in eastern Colorado during the 1997, -98, and -99 seasons. Treatments consisted of a combination of two hybrids (early and late maturity) and four plant densities (24 692, 37 037, 49 382 and 61 727 plants ha -1) seeded in replicated long strips. At maturity, yield was measured with a yield-mapping combine. Nine landscape attributes including elevation, slope, soil brightness (SB) (red, green, and blue bands of image), EC a (shallow and deep readings), pH, and soil organic matter (SOM) were also assessed. An analysis of treatment yields and landscape data, to assess for spatial dependency, along with semi variance analysis, and block kriging were used to produce kriged layers (10 m grids). Linear correlation and multiple linear regression analysis were used to determine associations between kriged average yields and landscape attributes. Yield monitor data revealed considerable variability in the three fields, with average yields ranging from 5.43 to 6.39 Mg ha -1 and CVs ranging from 20% to 29%. Hybrids responded similarly to field variation while plant densities responded differentially. Economically optimum plant densities changed by around 5000 plants ha -1 between high and low-yielding field areas, producing a potential savings in seed costs of $6.25 ha -1. Variability in yield across the three landscapes was highly associated with landscape attributes, especially elevation and SB, with various combinations of landscape attributes accounting for 47%, 95%, and 76% of the spatial variability in grain yields for the 1997, -98, and -99 sites, respectively. Our results suggest site-specific management of plant densities may be feasible.