• Authors:
    • Suyker, A. E.
    • Verma, S. B.
  • Source: Agricultural and Forest Meteorology
  • Volume: 150
  • Issue: 4
  • Year: 2010
  • Summary: Continuous measurements of CO 2 and water vapor exchanges made in three cropping systems (irrigated continuous maize, irrigated maize-soybean rotation, and rainfed maize-soybean rotation) in eastern Nebraska, USA during 6 years are discussed. Close coupling between seasonal distributions of gross primary production (GPP) and evapotranspiration (ET) were observed in each growing season. Mean growing season totals of GPP in irrigated maize and soybean were 1738114 and 99669 g C m -2, respectively (standard deviation). Corresponding mean values of growing season ET totals were 54527 and 45423 mm, respectively. Irrigation affected GPP and ET similarly, both growing season totals were about 10% higher than those of corresponding rainfed crops. Maize, under both irrigated and rainfed conditions, fixed 74% more carbon than soybean while using only 12-20% more water. The green leaf area index (LAI) explained substantial portions (91% for maize and 90% for soybean) of the variability in GPP PAR (GPP over a narrow range of incident photosynthetically active radiation) and in ET/ET o (71% for maize and 75% for soybean, ET o is the reference evapotranspiration). Water productivity (WP or water use efficiency) is defined here as the ratio of cumulative GPP or above-ground biomass and ET (photosynthetic water productivity=SigmaGPP/SigmaET and biomass water productivity=above-ground biomass/SigmaET). When normalized by ET o, the photosynthetic water productivity (WP ETo) was 18.41.5 g C m -2 for maize and 12.01.0 g C m -2 for soybean. When normalized by ET o, the biomass water productivity (WP ETo) was 27.52.3 g DM m -2 for maize and 14.13.1 g DM m -2 for soybean. Comparisons of these results, among different years of measurement and management practices (continuous vs rotation cropping, irrigated vs rainfed) in this study and those from other locations, indicated the conservative nature of normalized water productivity, as also pointed out by previous investigators.
  • Authors:
    • Pires, C. S. S.
    • Medeiros, M. A. de
    • Gravina, C. S.
    • Langer, L. F.
    • Cavalcante, K. R.
    • Togni, P. H. B.
    • Fontes, E. M. G.
    • Sujii, E. R.
  • Source: Arquivos do Instituto Biologico Sao Paulo
  • Volume: 77
  • Issue: 4
  • Year: 2010
  • Summary: The adoption of cultural practices such as companion plants and the kind of irrigation system can benefit the community of natural enemies in the agroecosystem due to the increase of more favorable microhabitats available and as a source of alternative resources, mainly in periods of low precipitation. This study evaluated how the tomato+coriander intercrop and the kind of irrigation (drip and sprinkler) could benefit the community of natural enemies in the tomato agroecosystem. This work was carried out in the experimental field of Embrapa Hortalicas, Gama, DF, from September to November 2008. The tomatoes were planted in monoculture or with coriander (companion plant) and irrigated by drip and sprinkler irrigation (three replicates per treatment), forming two groups of experimental plots according to the kind of irrigation. The community of natural enemies was sampled by the direct observation of specimens on 20 tomatoes plants per plot and in the treatments. Coriander plants were shaken over a plastic tray for collection of insects. The abundance, richness and diversity of natural enemies were higher in tomato+coriander plots, regardless of the irrigation system. We observed more species of natural enemies in tomato monoculture plots when it was irrigated by sprinkler irrigation. However, the cultural practices adopted had a different effect on each species or group of species. Therefore, in periods of low precipitation, the tomato+coriander consortium associated with sprinkler irrigation can enhance the conservation of natural enemies in the organic tomato agroecosystem.
  • Authors:
    • Kapur, B.
    • Kanber, R.
    • Unlu, M.
  • Source: African Journal of Biotechnology
  • Volume: 9
  • Issue: 30
  • Year: 2010
  • Summary: Lysimeters are considered the standard for evapotranspiration (ET) measurements. However, these units are often not replicated and are few in number at any given location. The Bowen ratio-energy balance (BREB) is a micrometeorological method often used to estimate ET because of its simplicity, robustness, and cost. In this paper, ET of irrigated soybean ( Glycine max L.) was directly measured by weighing lysimeter and estimated by BREB method over a growing season in a semi-arid climate of eastern Mediterranean region. The study was conducted in Adana-Turkey during the summer of 2009 on a 0.12 ha area with a weighing lysimeter (2.0*2.0*2.5 m) located in the center of the field completely covered by well watered soybean where the prevailing direction of the wind and the upwind fetch was about 60 m. Cumulative evapotranspiration totals from the lysimeter and BREB methods were 354 and 405 mm, respectively. The BREB method showed a good performance for daily ET estimation when compared to values measured by lysimeter. This method, with a root mean square error (RMSE) of 0.79 mmd -1 and a 0.96 index of agreement, over-estimates lysimetric measurements by 15%. The BREB method also performs well compared with lysimetric measurements for hourly ET, but produces overestimation of 14% with RMSE of 0.128 mmh -1, and a 0.92 index of agreement.
  • Authors:
    • van Rensburg, L. D.
  • Source: South African Journal of Plant and Soil
  • Volume: 27
  • Issue: 1
  • Year: 2010
  • Summary: This is the third soil physics review to be published in South African Journal of Plant and Soil. In the previous reviews the focus was broad and covered almost every aspect of the subject, providing a comprehensive list of contributions in soil physics. For the 25th year anniversary celebration of South African Journal of Plant and Soil, I have chosen to narrow the scope and focus on advances in soil physics in relation to irrigation and dryland agriculture. From a bio-physical viewpoint, South African researchers have made a major contribution to the body of scientific knowledge about irrigation and its application, expressed mainly in the form of irrigation or crop models such as PUTU, SWB and BEWAB. Attention was also given to modern ways of irrigation scheduling based on continuous soil water monitoring. Several irrigation scheduling service providers have adapted their businesses accordingly, with the result that South Africa is probably the leading country in Africa with respect to soil water monitoring and associated communication technology. In contrast, the review has shown that at farm and irrigation scheme level, salt management requires urgent attention. This is necessary as a precautionary measure to protect our natural resources. In the second part of the review the contribution of soil physics in relation to tillage practices is explored, and in particular how these have modified the field water balance components in order to enhance yield and rain water productivity. Based on the results of field experiments, new relationships were established, viz, rainfall and maize yield; water storage and yield; runoff and surface coverage by crop residue mulches; tillage depth, texture and yield relationships. Lastly, the review also showed how the water balance on clay and duplex soils in semi-arid zones can be modified through in-field rainwater harvesting to increase their rain water productivity. This technology has enhanced the livelihoods of many communal families who have applied the technique in their homesteads.
  • Authors:
    • Paula Junior, T. J. de
    • Vieira, R. F.
    • Teixeira, H.
  • Source: Informe Agropecuario Pages:
  • Volume: 31
  • Issue: 254
  • Year: 2010
  • Summary: Despite the growth of bean production, those from small farms still accounts for significant percentage of the total production. Most produced are from Minas Gerais. Maximizing efficiency and minimizing production costs are important factors to increase the profits of small producers. The use of technology and exploitation of natural resources should guide the actions of farmers. Planting dates, cultivars, row spacing and plant density, cropping systems, maize-bean intercropping, irrigation, weed control, pests and diseases as well as practical information technologies from research that aimed at increasing the income of the farmer with the cultivation of beans should be addressed.
  • Authors:
    • Fang, M.
    • Witter, J. D.
    • Spongberg, A. L.
    • Wu, C. X.
    • Czajkowski, K. P.
  • Source: Environmental Science & Technology
  • Volume: 44
  • Issue: 16
  • Year: 2010
  • Summary: Many pharmaceuticals and personal care products (PPCPs) are commonly found in biosolids and effluents from wastewater treatment plants. Land application of these biosolids and the reclamation of treated wastewater can transfer those PPCPs into the terrestrial and aquatic environments, giving rise to potential accumulation in plants. In this work, a greenhouse experiment was used to study the uptake of three pharmaceuticals (carbamazepine, diphenhydramine, and fluoxetine) and two personal care products (triclosan and triclocarban) by an agriculturally important species, soybean ( Glycine max (L.) Merr.). Two treatments simulating biosolids application and wastewater irrigation were investigated. After growing for 60 and 110 days, plant tissues and soils were analyzed for target compounds. Carbamazepine, triclosan, and triclocarban were found to be concentrated in root tissues and translocated into above ground parts including beans, whereas accumulation and translocation for diphenhydramine and fluoxetine was limited. The uptake of selected compounds differed by treatment, with biosolids application resulting in higher plant concentrations, likely due to higher loading. However, compounds introduced by irrigation appeared to be more available for uptake and translocation. Degradation is the main mechanism for the dissipation of selected compounds in biosolids applied soils, and the presence of soybean plants had no significant effect on sorption. Data from two different harvests suggest that the uptake from soil to root and translocation from root to leaf may be rate limited for triclosan and triclocarban and metabolism may occur within the plant for carbamazepine.
  • Authors:
    • Liu, W. J.
    • Yang, R.
  • Source: Environmental Earth Sciences
  • Volume: 61
  • Issue: 1
  • Year: 2010
  • Summary: In order to assess the extent of groundwater contamination by nitrate (NO 3--N) and to provide information about the deterioration of the groundwater quality in Zhangye Oasis, Northwest China, a study was conducted in this area. The mean value of NO 3--N concentrations in groundwater samples was 10.660.19 mg l -1. NO 3--N concentrations exceeding 10 mg l -1 (the threshold for drinking water set by the World Health Organization) were found in 32.4% of 71 wells, and were 13, 33.3, 52.4 and 50.0% in the groundwater samples from drinking wells, irrigation wells, hand-pumping wells and groundwater table observation wells, respectively. The result showed that the groundwater samples that had NO 3--N concentrations exceeding the threshold for drinking water were mostly collected from a depth of less than 20 m. Groundwater NO 3--N concentrations in areas used for the cultivation of vegetables, seed maize and intercropped maize were significantly higher than those in urban or paddy areas. NO 3--N contamination of groundwater in areas with sandy soil was more severe than in those with loam soil.
  • Authors:
    • Zhang, L. X.
    • Boahen, S.
  • Source: Agriculture and Biology Journal of North America
  • Volume: 1
  • Issue: 4
  • Year: 2010
  • Summary: One of the major problems associated with the early soybean production system (ESPS) in the Midsouth USA is seed shattering of early maturity group (MG) soybean that mature in the midsummer. Information is needed to measure the impact of this problem and to provide proper management strategies. Studies were conducted to investigate the problem of shattering in MG IV soybean, the dominant soybean group in ESPS, in 2006 and 2007. The objectives of this study were to determine the pattern and critical period of seed shattering of MG IV soybeans under various climatic and production conditions in the Mississippi Delta. A total of 56 and 80 MG IV soybean varieties were evaluated in the experiments in 2006 and 2007, respectively. The varieties were all selected from a Mississippi Soybean Variety Trial and the study was carried out at Stoneville, Mississippi. In 2006, only the April planting (April 19) under irrigation was investigated. In 2007, experiments were conducted on both irrigated and non-irrigated fields. On the irrigated tests, both April (April 23) and May (May 15) planting were examined. Results from both years have indicated that most pods of early MG IV soybean varieties can hold seeds relatively well for the first three weeks after maturity (WAM). However, differences were noted starting from the fourth WAM. Non-irrigated soybean shattered faster than irrigated soybean after three weeks. Irrigated soybean held seeds longer than non-irrigated soybean during the fourth week; however, seed shattering became greater after four weeks even in the irrigated study. When comparing early- and late-planted soybean under irrigated conditions, the later maturing pods held seeds better within the same period after maturity (up to 6 weeks or longer). Late-maturing pods tended to held seed better, most likely due to lower temperatures experienced after late September.
  • Authors:
    • Shi, C. L.
    • Jin, Z. Q.
    • Zhu, D. W.
  • Source: Jiangsu Journal of Agricultural Sciences
  • Volume: 26
  • Issue: 6
  • Year: 2010
  • Summary: In order to explore the effects of climate change on the crop production and agricultural vegetation on the carbon sequestration ability in the Northeast China in the future, the CERES models ran under both baseline weather and climate change scenarios, which were based on 3 global climate models (GCMs) of GISS, GFDL and UKMO, were used to evaluate the effects of climate change on productivities, moisture status and carbon sequestration of soybean, maize, spring wheat and rice in the Northeast China. In 2040, the growth duration of maize and rice would be shortened by 27 d and 29 d, respectively, while 13 d and 9 d were shortened by for soybean and spring wheat, respectively. The simulated soybean biomass under rainfed scenario was averagely 50% higher than that under the baseline weather, while 10% and 6% increments were simulated for irrigated rice and rainfed maize, respectively. The simulated biomass of rainfed spring wheat would be vulnerable to the climate change. The carbon sequestration ability of crops in the Northeast China would be enhanced from 3.82 t/hm 2 to 4.39 t/hm 2 by the climate change. The results indicated that the climate in the Northeast China would display a warm-dry tendency, and the warming climate would shorten the growth period of crops. The soybean productivities would increase significantly in scenarios of doubled CO 2, and rice and maize productivities would increase slightly, while spring wheat productivities would be unstable due to its sensibility to the moisture. Currently, compared with other regions, the crop carbon sequestration ability in the Northeast China was relative weak, while the climate change in the future would be beneficial for the improvement of crop productivities and the strengthening of agricultural carbon pool.
  • Authors:
    • Nobrega, L. H. P.
    • Smanhotto, A.
    • Sampaio, S. C.
    • Caovilla, F. A.
    • Queiroz, M. M. F. de
    • Gomes, B. M.
  • Source: Revista Brasileira de Engenharia Agricola e Ambiental
  • Volume: 14
  • Issue: 7
  • Year: 2010
  • Summary: In this work the distribution was evaluated "in situ" of phosphorus (P), organic matter (MO), potassium (K), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC), aluminum (Al), sum of bases (S), base saturation (V) and pH of a soil cultivated with soybean and irrigated with swine wastewater in the 0, 25, 50 and 75% levels. The factorial scheme was constituted by the 20, 40 and 60 cm soil depths and four wastewater levels with five repetitions. The results showed that significant difference occurred only for P, K and CEC in the soil profile. However, in all parameters, the 60 cm soil depth showed that the concentrations levels are similar to before the application of treatments.