• 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:
    • Nelson, L. A.
    • Baltensperger, D. D.
    • Eskridge, K. M.
    • Russell, W. K.
    • Guillen-Portal, F. R.
    • D'Croz-Mason, N. E.
    • Johnson, B. E.
  • Source: Crop Science
  • Volume: 44
  • Issue: 5
  • Year: 2004
  • Summary: Dryland maize ( Zea mays L.) production in the U.S. western High Plains is hampered by variable yields because of substantial environmental variation in this region. This study was conducted to determine the degree to which the ranking of superior maize hybrids for dryland production in the western High Plains was predictable from performance of the same hybrids in highly productive, irrigated environments in the same region. Forty-five maize hybrids were evaluated for grain yield performance under different water regimes in western Nebraska, eastern Wyoming, and northeastern Colorado in 1998 and 1999. The value of genotypic variance was by far larger in fully irrigated test environments (0.70) than in nonirrigated test environments (0.01-0.17). The genotypic mean repeatability in fully irrigated test environments (0.63) compared with that in nonirrigated test environments (0.18-0.69, respectively), and it showed correspondence with yield performance. The genetic correlation between fully and nonirrigated environments (0.72) was lower than that observed between all-nonirrigated environments (0.78-1.02). Thus, the proportion of direct advance in the former case (0.63) was generally lower than in the latter (0.41-0.97). However, an environmental similarity ratio (ESR) derived from crossover interaction indicated that water-contrasting environments were as similar (ESR=0.53) as nonirrigated environments (ESR=0.49) in ranking the maize hybrids. Selective identification of maize hybrids in irrigated environments for production under nonirrigated environments in the western High Plains might be a useful surrogate to direct selection in the latter environments.
  • Authors:
    • Silva, E. M. da
    • Rauber, J. C.
    • Azevedo, J. A. de
    • Reatto, A.
  • Source: Boletim de Pesquisa e Desenvolvimento - Embrapa Cerrados
  • Issue: 101
  • Year: 2003
  • Summary: The no-till system have positive impacts in soil and water conservation. This work aims to evaluate the main modifications on the soil physical properties caused by no-till system, carried out during 3, 6, and 12 years under rainfed conditions. The cases of direct drilling for five years under irrigated condition, a conventional tillage system, and a soil condition under natural Biome Cerrado were also evaluated in the Ampessan farm, Cabeceiras, Goias, Brazil. The soil physical characteristics were evaluated by samples taken from the following layers: 0-5, 2.5-7.5, 5-10, 10-15, 20-25, 42.5-47.5 and 72.5-77.5 cm. The infiltration characteristics were evaluated at 12 and 80 cm soil depth, using the Guelph permeameter to determine the field saturated hydraulic conductivity. The results showed that the intense soil mechanization on irrigated condition favoured a significant decrease in the field saturated hydraulic conductivity in the layers near to the soil surface. There was a tendency for higher water availability in the cultivated soils, in relation to that under natural soil environment, up to 22.5 cm soil depth.
  • Authors:
    • Nunes, R. P.
    • Pinho, J. L. N.
    • Silva, J. B. F.
    • Pitombeira, J. B.
    • Cavalcante Junior, A. T.
  • Source: Planta Daninha
  • Volume: 21
  • Issue: 1
  • Year: 2003
  • Summary: A study was conducted from September to December 1997, in Pentecoste, Ceara, Brazil, to determine the effectiveness of the herbicides glyphosate (1800 g ha -1) and paraquat (800 g ha -1), applied as desiccants before sowing, and fenoxaprop-P-ethyl [fenoxaprop-P] (0, 40, 80 and 120 g ha -1) and imazamox (0, 21, 42 and 63 g ha -1), applied in post-emergence conditions, in controlling the weeds and to evaluate the phytotoxicity of the herbicides to cowpea plants ( Vigna unguiculata cv. Epace 10) under a no-tillage system with furrow irrigation. The treatments with glyphosate associated with imazamox or fenoxaprop-P-ethyl was more efficient in controlling the weeds, showing reduced weed shoot dry biomass production, when compared to paraquat combined with the post-emergence herbicides. Fenoxaprop-P-ethyl and imazamox did not cause visual phytotoxicity symptoms to the cowpea plants. The best post-emergence weed control was provided by fenoxaprop-P-ethyl at the rate of 80 g ha -1, associated with glyphosate (1800 g ha 1). Fenoxaprop-P-ethyl was effective against the grass weeds, but not against Cenchrus echinatus and Digitaria horizontalis. Imazamox was not effective in controlling the broadleaf weeds Chamaesyce hirta and Euphorbia heterophylla at the studied rates.
  • Authors:
    • Hutchinson, R. L.
    • Boquet, D. J.
    • Paxton, K. W.
  • Source: Louisiana Agriculture
  • Volume: 46
  • Issue: 2
  • Year: 2003
  • Summary: Studies were conducted in Louisiana, USA, between 1987 and 2002 to determine the effects of tillage practices (no-till and surface till), cover crops (winter wheat, winter hairy vetch and volunteer winter native (fallow) vegetation) and nitrogen rates (0, 35, 70, 105 and 140 pounds per acre) under rainfed or irrigated conditions on cotton growth and yield. Following a cotton crop and without additional fertilizer, the native, vetch and wheat cover crops produced an average 1054, 2054 and 4045 pounds above-ground biomass per acre, respectively. Nitrogen concentration of the cover crop vegetation averaged 2.0, 4.0 and 1.5% in native, vetch and wheat, respectively. The total nitrogen in the cover crop biomass averaged across year, tillage regime and nitrogen rate was 27, 90 and 38 pounds per acre in native, vetch and wheat, respectively. Initially, lint yields in surface-till and no-till were similar but, after five years, no-till yields were higher. No cover crop + tillage treatment recorded the lowest yield. Savings in equipment and labour costs increased the returns for cotton grown with no-till practices. Cotton following vetch needed no nitrogen fertilizer. Cotton following wheat required high nitrogen rates for optimum yield. At the optimum nitrogen rate, all tillage cover crop regimes produced similar yields. Lint yields were lower in rainfed than irrigated conditions. Wheat cover crop was more beneficial to yield in rainfed than irrigated cotton. No-till + wheat cover crop recorded the highest yields and returns from rainfed cotton. No-till cotton produced yields similar to or higher than cotton planted in surface-till treatments.
  • Authors:
    • Jackson, LE
    • Burger, M.
  • Source: Soil Biology and Biochemistry
  • Volume: 35
  • Issue: 1
  • Year: 2003
  • Summary: Agricultural systems that receive high or low organic matter (OM) inputs would be expected to differ in soil nitrogen (N) transformation rates and fates of ammonium (NH4+) and nitrate (NO3-). To compare NH4+ availability, competition between nitrifiers and heterotrophic microorganisms for NH4+ and microbial NO3- assimilation in an organic vs. a conventional irrigated cropping system in the California Central Valley, chemical and biological soil assays, N-15 isotope pool dilution and N-15 tracer techniques were used. Potentially mineralizable N (PMN) and hot minus cold KCl-extracted NH4+ as indicators of soil N supplying capacity were measured five times during the tomato growing season. At mid-season, rates of gross ammonification and gross nitrification after rewetting dry soil were measured in microcosms. Microbial immobilization of NO3- and NH4+ was estimated based on the uptake of N-15 and gross consumption rates. Gross ammonification, PMN, and hot minus cold KCl-extracted NH4+ were approximately twice as high in the organically than the conventionally managed soil. Net estimated microbial NO3- assimilation rates were between 32 and 35% of gross nitrification rates in the conventional and between 37 and 46% in the organic system. In both soils, microbes assimilated more NO3- than NH4+. Heterotrophic microbes assimilated less NH4+ than No-3(-) probably because NH4+ concentrations were low and competition by nitrifiers was 'apparently strong. The high OM input organic system released NH4+ in a gradual manner and, compared to the low OM input conventional system, supported a more active microbial biomass with greater N demand that was met mainly by NO3- immobilization. (C) 2003 Elsevier Science Ltd. All rights reserved.
  • Authors:
    • Jacobsen, J. S.
    • Jones, C. A.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 34
  • Issue: 13/14
  • Year: 2003
  • Summary: Granular phosphorus (P) fertilizers are often treated with coatings, such as oil or wax, to decrease dust production during packaging, shipping, storage, and spreading. Unconfirmed reports from the field suggest these coatings may negatively impact plant response to applied P fertilizers. A three-phase study was conducted in Montana, USA to determine if these coatings significantly affect P dissolution rates, soil P test levels, P uptake, or yield. Coated and uncoated monoammonium phosphate granules were obtained from two fertilizer manufacturers. In Phase I, fertilizer dissolution rates in water were measured for fertilizer application rates representing both irrigated and dryland conditions. In Phase II, dissolution rates were evaluated in an acid-washed sand at two moisture contents. In Phase III, Olsen P, P uptake, and dry biomass in maize ( Zea mays) were measured in a low pH and high pH soil for both broadcast and incorporated fertilizer applications. Dust control coatings did not significantly decrease dissolution rates, Olsen P levels, P uptake amounts, or biomass for any of the treatments or at any time. In a small percentage of comparisons, coatings significantly increased solubility, Olsen P levels, P uptake, or biomass; although, in general, coatings caused no significant differences in these parameters.
  • Authors:
    • Hubbard, K. G.
    • Mahmood, R.
  • Source: Journal of Hydrology
  • Volume: 280
  • Issue: 1/4
  • Year: 2003
  • Summary: Soil moisture (SM) plays an important role in land surface and atmospheric interactions. It modifies energy balance at the surface and the rate of water cycling between the land and atmosphere. In this paper we provide a sensitivity assessment of SM and ET for heterogeneous soil physical properties and for three land uses including irrigated maize, rainfed maize, and grass at a climatological time-scale by using a water balance model. Not surprisingly, the study finds increased soil water content in the root zone throughout the year under irrigated farming. Soil water depletes to its lowest level under rainfed maize cultivation. We find a 'land use' effect as high as 36 percent of annual total evapotranspiration, under irrigated maize compared to rainfed maize and grass, respectively. Sensitivity analyses consisting of comparative simulations using the model show that soil characteristics, like water holding capacity, influence SM in the root zone and affect seasonal total ET estimates at the climatological time-scale. This 'soils' effect is smaller than the 'land use' effect associated with irrigation but, it is a source of consistent bias for both SM and ET estimates. The 'climate' effect basically masks the 'soils' effect under wet conditions. These results lead us to conclude that appropriate representation of land use, soils, and climate are necessary to accurately represent the water and energy balance in real landscapes.
  • Authors:
    • Mir, Z.
    • Acharya, S. N.
    • Moyer, J. R.
    • Doram, R. C.
  • Source: Canadian Journal of Plant Science
  • Volume: 83
  • Issue: 1
  • Year: 2003
  • Summary: Fenugreek (Trigonella foenum-graecom L.) is an annual legume that has potential as a forage crop on the Canadian Prairies. Experiments were established to determine the tolerance of fenugreek to several herbicides and their efficacy on various weeds. Potentially, fenugreek could be grown in conservation tillage systems in rotation with other annual crops. Therefore, additional multi-factor experiments were conducted to determine the effect of herbicides, seeding method, and 11 previous crops on fenugreek yield. Without herbicide application, weeds contributed 37 to 86% to total dry matter production. When imazamox/imazethapyr, or-combinations of imazamoz/imazethapyr or imazethapyr with ethalfluralin was applied, weed contents were about 5% of the total dry matter and the herbicides did not reduce fenugreek yield compared to the hand-weeded check. Total forage samples with a low weed content had lower fibre content and higher protein and digestible dry matter content than forages with a high weed content. When imazamox/imazethapyr was used for weed control, fenugreek yields and weed biomass were similar after direct seeding and after cultivation plus seeding. In addition, the effect of previous crop and the previous crop by seeding method interaction was not significant for fenugreek yield and weed biomass. Therefore, irrigated fenugreek can be successfully grown in conservation tillage systems in rotation with several crops provided an effective herbicide is used for weed control.
  • Authors:
    • Counce, P. C.
    • Gordon, E. C.
    • Keisling, T. C.
    • Oliver, L. R.
    • Manning, P. M.
    • Popp, M. P.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 34
  • Issue: 19/20
  • Year: 2003
  • Summary: Clay soils are difficult to manage to obtain a soyabean [ Glycine max (L.) Merr.] stand, especially when dry. A novel production system, recently observed on several farms in Arkansas, consists of bedding the dry clayey soil with disk-bedders, broadcasting the soyabean seed over the surface, re-bedding the seedbed to cover the seed, rolling the beds to flatten the tops and finally furrow irrigating immediately thereafter. Typically this planting system provides a stand of soyabean within 4 to 6 days after irrigation and is designated as "hipped" after the common reference of a disk-bedder as a hipper. Studies were conducted on Sharkey soil at Keiser, AR from 1998 to 2000 for comparing this "hipped" system to more widely used planting methods. On dry clayey soils, a randomized complete block design with three replications was used to compare full-season soyabean under a conventional 96-cm row system, drilled-planting into a stale seedbed, and the "hipped" system. A similar study for double-cropped wheat-soybean involved straw management (burn or leave) coupled with no-till drill, tilled drill, and "hipped" systems. Other small studies on the "hipped" system were conducted to investigate the sensitivity to planting depth, soyabean plant population, and suitability for obtaining a stand on other crops such as cotton [ Gossypium hirsutum (L.)] and grain sorghum [ Sorghum bicolor (L.) Moench]. The "hipped" system worked well for obtaining stands of soyabean, cotton, and grain sorghum. In essence the "hipped" system (1) provides insurance against poor planting conditions; (2) allows for a reduction in the uncertainty of planting and stand establishment time required; (3) can be used to achieve high plant populations; (4) requires a relatively higher seeding rate in double-crop than full-season systems; (5) shows promise for situations when wheat stubble burning becomes curtailed especially if planting can occur early to lead to improved canopy coverage and (6) leads to yield reductions in fields where depth of seed placement cannot be controlled easily.