• Authors:
    • Nichols ,R. L.
    • Webster, T. M.
  • Source: Weed Science
  • Volume: 60
  • Issue: 2
  • Year: 2012
  • Summary: Changes in the weed flora of cropping systems reflect the impacts of factors that create safe sites for weed establishment and facilitate the influx and losses to and from the soil seedbank. This analysis of the annual surveys of the Southern Weed Science Society documents changes in the weed flora of the 14 contiguous southern states since the advent of transgenic, herbicide-resistant crops. In 1994 and 2009, the top five weeds in corn were morningglories, Texas millet, broadleaf signalgrass, johnsongrass, and sicklepod; in this same period Palmer amaranth, smartweeds, and goosegrass had the greatest increases in importance in corn. In cotton, morningglories and nutsedges were among the top five most troublesome weeds in 1995 and 2009. Palmer amaranth, pigweeds, and Florida pusley were also among the five most troublesome species in 2009; the weeds with the largest increases in importance in cotton were common ragweed and two species with tolerance to glyphosate, Benghal dayflower and Florida pusley. In soybean, morningglories, nutsedges, and sicklepod were among the top five weed species in 1995 and 2009. Two species with glyphosate resistance, Palmer amaranth and horseweed, were the second and fourth most troublesome weeds of soybean in 2009. In wheat, the top four weeds in 2008 were the same as those in 1994 and included Italian ryegrass, wild garlic, wild radish, and henbit. Crop production in the southern region is a mosaic of various crop rotations, soil types, and types of tillage. During the interval between the surveys, the predominant change in weed management practices in the region and the nation was the onset and rapid dominance of the use of glyphosate in herbicide-resistant cultivars of corn, cotton, and soybean. Because of the correspondence between the effects of glyphosate on the respective weed species and the observed changes in the weed flora of the crops, it is likely the very broad use of glyphosate was a key component shaping the changes in weed flora. Only eight of the top 15 most troublesome weeds of cotton and soybean, the crops with the greatest use of glyphosate, were the same in 1995 and 2009. In contrast, in corn and wheat where adoption of glyphosate-resistant cultivars lags or is absent, 12 of the 15 most troublesome weeds were the same in 1994 and 2008. These findings show on a regional scale that weeds adapt to recurrent selection from herbicides, currently the predominant weed management tool. Future research should seek methods to hinder the rapid spread of herbicide-tolerant and evolution of herbicide-resistant weed species. As new tools are developed, research should focus on ways to preserve the efficacy of those tools through improved stewardship. Nomenclature: annual bluegrass, Poa annua L. POAAN; Benghal dayflower, Commelina benghalensis L. COMBE; broadleaf signalgrass, Urochloa platyphylla (Nash) R.D. Webster BRAPP; common ragweed, Ambrosia artemisiifolia L. AMBEL; Florida pusley Richardia scabra L. RCHSC; goosegrass Eleusine indica (L.) Gaertn. ELEIN; groundcherries, Physalis spp.; henbit, Lamium amplexicaule L. LAMAM; horseweed, Conyza canadensis (L.) Cronq. ERICA; Italian ryegrass, Lolium perenne L. ssp. multiflorum (Lam.) Husnot LOLMU; johnsongrass, Sorghum halepense (L.) Pers. SORHA; morningglories, Ipomoea spp.; nutsedges, Cyperus spp.; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; pigweed, Amaranthus spp.; sicklepod, Senna obtusifolia (L.) H.S. Irwin & Barneby CASOB; smartweeds, Polygonum spp.; Texas millet, Urochloa texana (Buckl.) R. Webster PANTE; wild garlic, Allium vineale L. ALLVI; wild radish, Raphanus raphanistrum L. RAPRA; corn, Zea mays L.; cotton, Gossypium hirsutum L.; soybean Glycine max. (L.) Merr.; wheat, Triticum aestivum L.
  • Authors:
    • Hayes, R. M.
    • McClure, M. A.
    • Yin, X. H.
  • Source: Agricultural Sciences
  • Volume: 3
  • Issue: 2
  • Year: 2012
  • Summary: Nitrogen concentration in the ear leaf is a good indicator of corn (Zea mays L.) N nutrition status during late growing season. This study was done to examine the relationship of late-season ear leaf N concentration with early- to mid-season plant height of corn at Milan, TN from 2008 to 2010 using linear, quadratic, square root, logarithmic, and exponential models. Six N rate treatments (0, 62, 123, 185, 247, and 308 kg.N.ha -1) repeated four times were implemented each year in a randomized complete block design under four major cropping systems: corn after corn, corn after soybean [Glycine max (L.) Merr.], corn after cotton [Gossypium hirsutum (L.)], and irrigated corn after soybean. The relationship of ear leaf N concentration determined at the blister growth stage (R 2) with plant height measured at the 6-leaf (V6), 10-leaf (V10), and 12-leaf (V12) growth stages was statistically significant and positive in non-irrigated corn under normal weather conditions. However, the strength of this relationship was weak to moderate with the determination coefficient (R 2) values ranging from 0.21 to 0.51. This relationship was generally improved as the growing season progressed from V6 to V12. Irrigation and abnormal weather seemed to have adverse effects on this relationship. The five regression models performed similarly in the evaluation of this relationship regardless of growth stage, year, and cropping system. Our results suggest that unlike the relationship of corn yield at harvest with plant height measured during early- to mid-season or the relationship of leaf N concentration with plant height when both are measured simultaneously during early- to mid-season, the relationship of late-season ear leaf N concentration with early- to mid-season plant height may not be strong enough to be used to develop algorithms for variable-rate N applications on corn within a field no matter which regression model is used to describe this relationship.
  • Authors:
    • Wu, Z. B.
    • Shi, Y. J.
    • Song, F. H.
    • Yishake, H.
    • Yu, T.
  • Source: Xinjiang Agricultural Sciences
  • Volume: 49
  • Issue: 1
  • Year: 2012
  • Summary: Objective: The spatial distribution characteristics of jujube tree fine roots in the jujube-cotton intercorpping were analyzed in order to provide the basic documents for constructing the model of water uptake by roots, and for determining the width of jujube protection and improving irrigation and fertilization technology. Method: Root excavation was used and a soil sample for each side of the live root was picked, cleaned, dried, sorted, scanned. Specialized software was used to measure and analyze the root length and other indicators. Result: (1) In the vertical direction, jujube trees fine roots are mainly distributed in the soil layer of 0-120 cm, accounting for 87.09% of the total; (2) in the horizontal direction, they are mainly distributed in the range of 0-150 cm between the jujube trees, accounting for 83.67% of the total amount; (3) according to the distribution of cotton roots, jujube and cotton roots are mainly distributed in the range of 0-150 cm between the jujube trees at the depth of 0-80 cm of the soil layer. Conclusion: Establishment of protection for root growth of the jujube trees played an extremely important role in the relief of the water and nutrient competition between cotton and jujube trees, but the width of protection setting is still worthy of further consideration, which would be involved in the comprehensive judgments of jujube tree age, crown, etc. In view of the present test situation, the zone of fertilization to jujube trees should be within the range of 100-150 cm without changing the test protection.
  • Authors:
    • Kunkel, K.
    • Reddy, K. R.
    • Gao, W.
    • Xu, M.
    • Liang, X. Z.
    • Schmoldt, D. L.
    • Samel, A. N.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Climate variability and changes affect crop yields by causing climatic stresses during various stages of the plant life cycle. A crop growth model must be able to capture the observed relationships between crop yields and climate stresses before its credible use as a prediction tool. This study evaluated the ability of the geographically distributed cotton growth model redeveloped from GOSSYM in simulating U.S. cotton ( Gossypium hirsutum L.) yields and their responses to climate stresses during 1979 to 2005. Driven by realistic climate conditions, the model reproduced long-term mean cotton yields within 10% of observations at the 30-km model resolution across virtually the entire U.S. Cotton Belt and correctly captured the critical dependence of their geographic distributions on regional climate characteristics. Significant correlations between simulated and observed interannual variations were found across 87% of the total harvest grids. The model also faithfully represented the predictive role of July to August air temperature and August to September soil temperature anomalies on interannual cotton yield changes on unirrigated lands, with a similar but weaker predictive signal for irrigated lands as observed. The modeled cotton yields exhibited large, positive correlations with July to August leaf area index. These results indicate the model's ability to depict the regional impact of climate stresses on cotton yields and suggest the potential predictive value of satellite retrievals. They also provide a baseline reference for further model improvements and applications in the future study of climate-cotton interactions.
  • Authors:
    • Hubbs, M. D.
    • Franzluebbers, A. J.
    • Norfleet, M. L.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Simulation models that are sensitive to management, edaphic factors, and climate could provide insights into how land owners and producers might be able to sequester soil organic carbon (C) and engage in emerging carbon markets. In this study, the soil conditioning index (SCI) embedded in the Revised Universal Soil Loss Equation (RUSLE2) model was used to predict (1) potential soil organic C sequestration under conventional and conservation management of a diversity of cotton cropping systems throughout the Cotton Belt and (2) relative influences of soil texture, slope, climatic conditions, and management on potential soil organic C sequestration. Across 10 regions of the Cotton Belt, SCI scores ranked in the following order: perennial pasture > no-till cropping systems > conventional tillage cotton. Variations in significance of SCI scores occurred among 5 different no-till cropping systems within regions of the Cotton Belt. For example, 7 of the 10 regions had significantly (p <= 0.05) greater SCI scores (linked to greater soil organic C sequestration) when monoculture cotton was grown with winter cover crop than without.Variation in SCI was dominated by management (46%) and slope (24%) and very little affected by climate (7%) and soil texture (1%). Increasingly wetter climatic conditions (as expressed by increasing precipitation to potential evapotranspiration) had a negative influence on SCI scores for all management systems and land slopes evaluated, but particularly for moldboard-plowed cotton on sloping land, With a linear relationship between SCI and soil organic C sequestration, predicted soil organic C sequestration averaged -0.31 +/- 0.19 Mg C ha(-1) y(--1) (-280 +/- 170 lb ac(-1) yr(-1)) under conventionally tilled cotton, 0.12 +/- 0.06 Mg C ha(-1) y(-1) (103 +/- 52 lb ac(-1) yr(-1)) under various no-till crop rotations, and 0.26 +/- 0.02 Mg C ha(-1) y(-1) (231 +/- 20 lb ac(-1) yr(-1)) under perennial pasture. Cotton production with conventional tillage could only be expected to maintain soil organic C under a best-case scenario and would lose substantial soil organic C under most other scenarios. Simulations showed the strong, positive influence that conservation agricultural management has to sequester soil organic C, irrespective of climate, slope, and texture.
  • Authors:
    • Tian, C.
    • Chen, F.
    • Wang, X.
    • Zhang, R.
    • Li, Z.
  • Source: PLOS ONE
  • Volume: 7
  • Issue: 11
  • Year: 2012
  • Summary: There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO2 concentrations. However, limited information exists regarding the potential for increased carbon sequestration of different management strategies. The objective of this study was to quantify and contrast carbon dioxide exchange in traditional non-mulching with flooding irrigation (TF) and plastic film mulching with drip irrigation (PM) cotton (Gossypium hirsutum L.) fields in northwest China. Net primary productivity (NPP), soil heterotrophic respiration (R-h) and net ecosystem productivity (NEP) were measured during the growing seasons in 2009 and 2010. As compared with TF, PM significantly increased the aboveground and belowground biomass and the NPP (340 g C m(-2) season(-1)) of cotton, and decreased the R-h (89 g C m(-2) season(-1)) (p < 0.05). In a growing season, PM had a higher carbon sequestration in terms of NEP of similar to 429 g C m(-2) season(-1) than the TF. These results demonstrate that conversion of this type of land use to mulching practices is an effective way to increase carbon sequestration in the short term in cotton systems of arid areas.
  • Authors:
    • Khamseh, A. R. M.
    • Ghotbi, M.
    • Dehaghi, M. A.
    • Rouhi, H. R.
    • Ghotbi, M.
    • Wahsha, M.
  • Source: International Journal of AgriScience
  • Volume: 2
  • Issue: 1
  • Year: 2012
  • Summary: Growing cover crops with allopathic characteristics is a way to biologically control the weed P. aegyptiaca. Allelochemicals are present in almost all plants and in many plant tissues including leaves, stems, flowers, fruits, seeds and roots. This experiment was conducted to compare effects of allopathic crops on the germination rate of P. aegyptiaca seeds. Weed infestations were tested in Polyethylene (PE) bags and pot experiments. 27 crops, of different families, were grown in 2-Kg pots containing sterile soil infested with 0.6 g of seed. The control pots contained only 0.6 g of P. aegyptiaca seeds. Two month-old plants were incorporated into the soil from the surface and then tomato seedlings ( Lycopersicum esculentum Mill.) were planted in the pots. Cotton (Malvaceae family) was among the cultured plants, used as a trap crop to thoroughly eradicate the threat of P. aegyptiaca. The most significant reduction in broomrape shoot and capsule number was demonstrated in those pots that contained cotton and sorghum, and in those that contained tomato; tomato dry weight significantly augmented. The results from the PE bags were in parallel with those of the pots. The germination rates of P. aegyptiaca (%) next to the plants in PE bags ranged from 8.333% to 55.333% respectively in millet and pepper. Except for sunflower, vetch, soy bean, chick pea, sainfoin, alfalfa, zucchini and sesame, which demonstrated catch crop, activity, the other cultivated plants; corn, oat, beet, sugar beet, triticale, caster-oil plant, millet, fiber flax, pepper, cotton and sorghum were determined as trap crops for the weed P. aegyptiaca.
  • Authors:
    • Mexal, J. G.
    • Steiner, R. L.
    • Sammis, T. W.
    • Shukla, M. K.
    • Sharma, P.
  • Source: Agricultural Water Management
  • Volume: 109
  • Year: 2012
  • Summary: Nitrate leaching is a common problem in frequently fertilized agricultural crops in Southern New Mexico. The objectives of this study were to estimate the leaching depths, irrigation and plant uptake efficiencies for onion (Album cepa L), chile (Capsicum annuum), and cotton (Gossypium spp.) crops. The study aims to determine how existing best management practices for these three specialty crops could be improved. Soil samples collected monthly for two growing seasons starting April 2007 to June 2010 were analyzed for NO3-N and chloride concentrations. The NO3-N loadings below the rooting zone varied from 22 to 92 kg ha(-1) during growing season 1 and 18-90 kg ha(-1) during growing season 2 in all the three experimental fields. The leaching fractions (LFs) varied from 0.09 to 0.21 during growing season 1 and 0.08-0.22 during growing season 2 in the experimental fields. The irrigation efficiencies (1E = 1 - LF) ranged from 79 to 91% during growing season 1 and from 78 to 92% during growing season 2 in all the three fields. Nitrogen application efficiencies (NAEs) varied from 39 to 75% during growing season 1 and 40-76% during growing season 2 in all the experimental fields. Under the prevalent management conditions, cotton field showed higher irrigation efficiency as well as the NAE as compared to onion and chile fields. Based on the soil N content at the end of growing seasons, the results indicate that reducing fertilizer applications until bulb formation in onions and flower initiation in chile can decrease the amount of fertilizer applications to as much as half, thus can help in reducing the NO3-N leaching and improving nitrogen and water efficiencies. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Dabar, S.
    • Soni, S. N.
  • Source: Journal of Soils and Crops
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: After the green revolution and the development stage of cotton production in India the acceptance of improved cotton production technology/practices was getting the prime attention for increasing their production and productivity. Cotton research schemes and several extension education programmes were introduced to offer the education and training to farmers in respect of adopting the viable and proven improved cotton production technology/practices for their practical utilization in order to increase the income. In this context study was conducted in Dhar district. Madhya Pradesh to know the technological adoption level of cotton growers and to find out the association between socio personal and economic attributes of cotton growers with level of adoption. The study was conducted in the year of 2008-09. The study revealed that in respect of overall technology adoption, maximum cotton growers 50.22% adopted high level of technology followed by 34.11% respondents who adopted medium level and 15.67% respondents adopted low level of improved cotton production technology on their farms. The high level of adoption were reported in various extent i.e. in case of irrigation management (60.00%) followed by insect control measure (58.00%), rhizobium culture (58.00%), seed treatment (55.00%), recommended dose of fertilizer (52.00%), method of sowing (47.00%), weed management (46.00%), pest control measure (41.00%) and improved variety of seed (35.00%) respectively. The Study also revealed postive nature of phenomena the relationship between socio personal and economic characteristics of cotton growers and adoption level of improved cotton production technology. The zero order correlation coefficient of characteristic of cotton growers depicted in respect of age was 0.470**, for caste 0.283**, for level of income 0.392**, for level of employment 0.468**, for social participation 0.289** and for size of family 0.431. These characteristics were found to positively significant with adoption level of cotton production technology at 0.01 level of probability respectively. On the other hand, the characteristics like size of land holding had the correlation coefficient value of 0.200*, for material possession 0.248*, for economic motivation 0.201*, for attitude towards improved practices 0.215* and for extension participation 0.247* and these values were found positively significant with adoption level of cotton production technology at 0.05 level of probability respectively.
  • Authors:
    • Dahiya, S. S.
    • Pannu, R. K.
    • Singh, M.
    • Dhaka, A. K.
  • Source: Crop Research
  • Volume: 43
  • Issue: 1-3
  • Year: 2012
  • Summary: The survey was conducted in Haryana state during rabi season of 2005-06 on 972 farmers in 54 villages of 16 districts with respective cropping system i. e. pearl millet-wheat, cotton-wheat and rice-wheat. The 18 farmers from each village were selected randomly covering small (4.0 ha) group of land holders. Only those farmers were selected, who had grown PBW 343 variety of wheat. The sample sizes for pearl millet-wheat, cotton-wheat and rice-wheat of all three small, medium and large farm size groups were 90, 108 and 126, respectively. Yield reported in rice-wheat system was higher than cotton-wheat and pearl millet-wheat system. Maximum yield was observed with the use of more than five bags urea/ha. Numbers of irrigations above 4 and seed rate above 100 kg/ha were also reported to increase in yield. Protein content of wheat in pearl millet-wheat system was the highest. Protein content in late sown wheat in pearl millet-wheat system was higher than cotton-wheat and rice-wheat systems. Seed rate of 100 kg/ha and nitrogen dose of five bags of urea/ha gave significantly higher protein content. Quantitative production of wheat in rice-wheat and cotton-wheat cropping systems was higher than pearl millet-wheat system but quality in. terms of protein content was significantly superior to both the rice-wheat and cotton-wheat systems. Hence, export market should be developed in quality grain producing zone i. e. in pearl millet-wheat growing areas, where lower percentage of farmers use higher nitrogen doses and cultivation practices were numerically better than other cropping systems.