421. Agronomic performance of phosphate fertilizers in an oxisol under no-tillage.; Eficiencia tecnica de fertilizantes fosfatados em latossolo sob plantio direto.

• Authors:
  • Bayer, C.
  • Vieira, R. C. B.
  • Fontoura, S. M. V.
  • Ernani, P. R.
  • Moraes, R. P. de
• Source: Revista Brasileira de Ciência do Solo
• Volume: 34
• Issue: 6
• Year: 2010
• Summary: Little is known about the agronomic effectiveness of phosphate rocks in high-yielding crop rotation systems under no-till in the Center-South of the state of Parana, Brazil. This field study was undertaken to compare the effectiveness of rock phosphates and soluble P fertilizers to increase the yield of several annual crops grown in two consecutive triennial crop-rotation cycles under no-tillage. The experiment was carried out in an Oxisol, in Guarapuava, PR, from 2000 until 2006. Two phosphate rocks (PR - Gafsa and Arad) and a soluble P fertilizer (TSP - triple superphosphate) were broadcast over the soil surface at rates of 0, 40, 80 and 160 kg ha -1 P 2O 5, at the beginning of the first and the second rotation cycle of the triennial crops (oat, maize, wheat, soybean, barley and soybean). With exception of barley, crop yields were not affected in the first rotation cycle by any phosphate fertilizer regardless of type and rate, probably due to the high P contents available in the soil (8.7 mg dm -3 in the 0-10 cm layer). In the second rotation cycle, when soil available P was 4.1 mg dm -3; P application at oat sowing increased the yield of summer crops by 11% and of winter crops by 20%. The yield increment was lowest for maize (8%) and highest for barley (44%). In this cycle, TSP resulted in higher yield than PR, though only for winter crops (oat, wheat and barley), in a mean of 11%, with no difference between Gafsa and Arad. Water soluble fertilizer (TSP) was more efficient than phosphate rocks in soils under no-till system both in the short and long term. Nevertheless, it is not necessary to apply phosphates for high yields in soils with high available P contents under no-till, except for species with high P requirement, e.g., barley.

422. Distribution of roots and root length density in a maize/soybean strip intercropping system.

• Authors:
  • Zhang, J. P.
  • Sun, J. S.
  • Liu, Z. G.
  • Qiu, X. Q.
  • Duan, A. W.
  • Gao, Y.
  • Wang, H. Z.
• Source: Agricultural Water Management
• Volume: 98
• Issue: 1
• Year: 2010
• Summary: In a field experiment in the Yellow River Basin conducted in 2007 and 2008, it was found that, under full irrigation, the roots of maize not only penetrated deeper than those of soybean but also extended into soybean stands underneath the space between inner rows of soybean. The roots of soybean, however, were confined mainly to the zone near the plants. Horizontal growth of the roots of both the crops was confined mainly to the soil layer 16-22 cm below the surface, a layer that lay above an existing plough pan. Root length density (RLD) was much higher in the top layer (0-30 cm deep) and in the zone closer to the plants. The exponential model proved suitable to describe the RLD vertically and horizontally in both sole cropping and in intercropping.

423. A biomass accumulation model for maize/soybean intercropping system.

• Authors:
  • Wang, H. Z.
  • Chen, J. P.
  • Zhang, J. P.
  • Qiu, X. Q.
  • Duan, A. W.
  • Gao, Y.
• Source: Chinese Journal of Eco-Agriculture
• Volume: 18
• Issue: 5
• Year: 2010
• Summary: In this study, a radiation interception and utilization model was developed through an experiment on maize/soybean intercropping systems with different intercropping proportions of maize and soybean to assess crop growth and yield. In the model, crop biomass and yield are calculated as functions of photosynthetic active radiation ( PAR), radiation interception fraction ( F) and radiation use efficiency ( RUE). PAR is estimated from ratios of PAR to solar radiation (). F is calculated by using the Keating and Carberry equation. Time for emergence, flowering and maturity are determined by growing degree days ( GDD) since planting. Results indicate that the model accurately simulates total biomass and yield of fully irrigated maize/soybean intercropping system.

424. Response of soybean genotypes to different irrigation regimes in a humid region of the southeastern USA.

• Authors:
  • Guerra, L. C.
  • Persson, T.
  • Garcia y Garcia, A.
  • Hoogenboom, G.
• Source: Agricultural Water Management
• Volume: 97
• Issue: 7
• Year: 2010
• Summary: Studies on irrigation scheduling for soybean have demonstrated that avoiding irrigation during the vegetative growth stages could result in yields as high as those obtained if the crop was fully irrigated during the entire growing season. This could ultimately also lead to an improvement of the irrigation water use efficiency. The objective of this study was to determine the effect of different irrigation regimes (IRs) on growth and yield of four soybean genotypes and to determine their irrigation water use efficiency. A field experiment consisting of three IR using a lateral move sprinkler system and four soybean genotypes was conducted at the Bledsoe Research Farm of The University of Georgia, USA. The irrigation treatments consisted of full season irrigated (FSI), start irrigation at flowering (SIF), and rainfed (RFD); the soybean genotypes represented maturity groups (MGs) V, VI, VII, and VIII. A completely randomized block design in a split-plot array with four replicates was used with IR as the main treatment and the soybean MGs as the sub-treatment. Weather variables and soil moisture were recorded with an automatic weather station located nearby, while rainfall and irrigation amounts were recorded with rain gauges located in the experimental field. Samplings for growth analysis of the plant and its components as well as leaf area index (LAI) and canopy height were obtained every 12 days. The irrigation water use efficiency ( IWUE) or ratio of the difference between irrigated and rainfed yield to the amount of irrigation water applied was estimated. The results showed significant differences ( P

425. Genotoxicity effect of nitrobenzene on soybean ( Glycine max) root tip cells.

• Authors:
  • Guo, C. H.
  • Li, R.
  • Ma, J.
  • Guo, D. L.
• Source: Journal of Hazardous Materials
• Volume: 178
• Issue: 1/3
• Year: 2010
• Summary: Nitrobenzene is a synthetic compound widely used in industry which can lead to environmental pollution. While the toxicity and carcinogenicity of nitrobenzene on humans and animals have been studied, less is known about its genotoxicity to plants. In this study, the genotoxic effects of nitrobenzene were investigated with growing soybean seedlings in solution culture. Compared with the control, the growth of soybean seedlings (taproot length, longest lateral root length and lateral roots number) decreased and showed statistics difference at nitrobenzene test concentration of 50 and 100 mg/L. Micronucleus, chromosomal bridge and others chromosomal aberrations were observed in soybean root tip cells exposed to nitrobenzene. Frequency of chromosomal aberrations increased linearly with nitrobenzene test concentration between 5 and 50 mg/L and decreased at 100 mg/L which showed significant difference between control and 25 mg/L or higher test concentration. Results of the present study suggest that nitrobenzene has genotoxicity on soybean root tip cells. The mechanism of genotoxicity of NB needs further study. It is concluded that high environmental levels of nitrobenzene in rivers, lakes and dam waters are hazardous to aquatic species and to irrigated plants.

426. An estimation of global virtual water flow and sources of water withdrawal for major crops and livestock products using a global hydrological model.

• Authors:
  • Kanae, S.
  • Inuzuka, T.
  • Hanasaki, N.
  • Oki, T.
• Source: Journal of Hydrology
• Volume: 384
• Issue: 3/4
• Year: 2010
• Summary: The concept of virtual water, which is the volume of water consumption required to produce commodities traded to an importing or exporting nation (or any region, company, individual, etc.), is a useful complement to water resource analyses of water availability and use by region. Identifying the source of virtual water, such as precipitation (green water) and irrigation water (blue water), further enhances this concept because each differs in the level of sustainability and opportunity cost. Recent improvements in global hydrological models consisting of both physically based hydrological and anthropogenic activity modules enabled us to simulate the virtual water content of major crops consistent with their global hydrological simulation. Enhancing one of these models, called H08, we were able to assess two major sources of virtual water flow or content simultaneously: green water and blue water. Blue water was further subdivided into three subcategories ( i.e., streamflow, medium-size reservoirs, and nonrenewable and nonlocal blue water). We conducted a global hydrological simulation for 15 years from 1985 to 1999 at a spatial resolution of 0.5degrees * 0.5degrees (longitude and latitude). Total precipitation on land was 113,900 km 3 yr -1, with 72,080 km 3 yr -1 on average evaporating in the period 1985-1999. Green water evapotranspiration from rainfed and irrigated cropland and blue water evapotranspiration from irrigated cropland was estimated at 7820, 1720, and 1530 km 3 yr -1, respectively. Next, using global trade data for 2000 and the simulated virtual water content of major crops, the virtual water flow was estimated globally. Our results indicated that the global virtual water export ( i.e., the volume of water that an exporting nation consumes to produce the commodities that it trades abroad) of five crops (barley, maize, rice, soybean, and wheat) and three livestock products (beef, pork, and chicken) is 545 km 3 yr -1. Of the total virtual water exports, 61 km 3 yr -1 (11%) are blue water ( i.e., irrigation water) and 26 km 3 yr -1 (5%) are nonrenewable and nonlocal blue water.

427. Phenotypic, genotypic and environmental correlations in soybean cultivated under an irrigated meadow in south of Tocantins state.; Correlacoes fenotipicas, genotipicas e ambientais em soja cultivada sob condicoes varzea irrigada, sul do Tocantins.

• Authors:
  • Peluzio, J. M.
  • Almeida, R. D. de
  • Afferri, F. S.
• Source: Bioscience Journal
• Volume: 26
• Issue: 1
• Year: 2010
• Summary: A trial was carried out to estimate the phenotypic, genotypic and environmental correlations between eight agronomic traits, in twelve cultivars of soybean. The essays were carried out at Formoso do Araguaia, TO, in the inter-cropping of 2007. The soybean cultivars studied were DM Vitoria, MG/BR 46 (Conquista), Suprema, BRS Pintado, DM 247, BRS MG 68, BRS MG Lideranca, BRS MG Seguranca, DM 339, BRS MG Garantia, A 7002 e DM 309. The genotypic correlations presented equal signs and, in most cases were higher than their correspondent phenotypic correlations, indicating that the phenotypic values were reduced by the environment. The correlations genotypic presented equal sign and, in most of the cases, superior values to their correspondents correlations phenotypic, indicating that the expression phenotypic is reduced before the influences of the atmosphere. Selection of late flowering plants and with height insertion of the first bean would make it possible to indirectly improve grains yield due to the positive and significant correlation between these traits.

428. Nematodes associated with soils and roots of field crops in northern Ghana.

• Authors:
  • Nutsugah, S. K.
  • Amponsah, N. T.
• Source: Pakistan Journal of Nematology
• Volume: 28
• Issue: 1
• Year: 2010
• Summary: Soils and roots of 10 field crops grown in Northern and Upper East Regions of northern Ghana were sampled for the presence of plant parasitic and non-plant-parasitic nematodes. Species belonging to Xiphmema, Longidorus and Hoplolaimus were the most predominant and significantly higher, whereas Tylenchorhynchus was the least common genus of plant parasitic nematodes found. Meloidogyne, Pratylenchus, Heterodera and Hirschmanniella spp. were frequently found associated with soils and roots of tomato, peanut, soybean and irrigated rice respectively. In all, 16 genera of plant parasitic nematodes and eight of non-plant parasitic nematodes were recorded with the most ubiquitous being Cephalobus spp., (non parasitic) in root and soil samples of all the 10 crops irrespective of host location. Findings from the survey however, had provided evidence showing that soils and roots of most major crops grown throughout northern Ghana were infected with several types of parasitic nematodes.

429. Weed Populations as Affected by Residue Management Practices in a Wheat-Soybean Double-Crop Production System

• Authors:
  • Kelley, J.
  • Oliver, D.
  • Gbur, E. E.
  • Brye, K. R.
  • Amuri, N.
• Source: Weed Science
• Volume: 58
• Issue: 3
• Year: 2010
• Summary: Management practices and cropping systems that serve as integrated weed management practices, and at the same time can contribute to improved soil quality, will be important for the sustainability of agricultural production systems. The objective of this study was to assess weed species population density under contrasting tillage (conventional tillage [CT] and no tillage [NT]), residue burning (burn and no burn), and residue level (low and high) treatments after 5 and 6 yr of consistent management in a wheat-soybean double-crop production system. A field experiment was conducted from fall 2001 to fall 2007 in the Mississippi River Delta region of eastern Arkansas on a Calloway silt-loam. Weed assessments were conducted twice during the soybean growing season, before (early season) and after herbicide application (late season) in 2006 and 2007. Total weed density was greater under CT (513 plants m(-2)) than under NT (340 plants m(-2)) early in the growing season in 2006, but was greater under NT than CT late in the season in 2007, suggesting that the effectiveness of glyphosate on total weeds differs between CT and NT. Averaged across residue levels, grass species density was greatest in the NT burn (68 to 167 plants m(-2)) combination and lowest in the NT no-burn (41 to 63 plants m(-2)) early in the growing season in both years. Broadleaf density was greater early (200 to 349 plants m(-2)) than late (18 to 20 plants m(-2)) in the growing season under both CT and NT in 2006, but in 2007 broadleaf density did not differ by tillage treatment between seasons. Perennial weed density was greater in the burn (99 plants m(-2)) than in the no-burn (59 plants m(-2)) treatment in 2006. No tillage, no burning, and a high residue level appeared to contribute to the suppression of most weed species without reducing herbicide efficiency.

430. Soybean yield correlated with the porosity and the density of a red Latosol of the Brazilian Savanna.; Produtividade da soja correlacionada com a porosidade e a densidade de um Latossolo Vermelho do cerrado brasileiro.

• Authors:
  • Basso, F. C.
  • Montanari, R.
  • Passos e Carvalho, M. de
  • Andreotti, M.
  • Pariz, C. M.
  • Azenha, M. V.
  • Vercese, F.
• Source: Ciência Rural
• Volume: 40
• Issue: 3
• Year: 2010
• Summary: The variation and the spatial dependence attributes of the following plant and soil characteristics: soyabean yield (SY) in no-till and irrigated soil; the macroporosity (MA); microporosity (MI); total porosity (TP); and bulk density (BD), in depths of 1 (0-0.10 m), 2 (0.10-0.20 m) and 3 (0.20-0.30 m), were studied in a Red Latosol of Mato Grosso do Sul, Brazil, were analysed during 2004/05, to study the variation and the linear and spatial correlations among the attributes (plant and soil) and select an index of soil physical quality with good capacity to represent the soyabean yield. A geostatistical grid to collect soil and plant data was installed, with 124 sample points, in an area of 4000 m 2. The linear relationship between soyabean yield and physical attributes of soil studied was low. So, there was a direct spatial relationship between SY and MA1 (0-0.10 m), as well as between SY and MA2 (0.10-0.20 m). The MA1 showed its best index of the soil physical quality, when it was destined to estimate the soyabean yield in no-till soil.