• Authors:
    • Schmidt, F.
    • Fortes, M. de A.
    • Bortolon, L.
    • Bortolon, E. S. O.
    • Sousa, R. O. de
  • Source: CIENCIA RURAL
  • Volume: 40
  • Issue: 5
  • Year: 2010
  • Summary: The poor drainage of wetland soils originates an anaerobic environment favoring the appearance of toxic substances, like acetic acid, which affects negatively the growth of dryland crops. The present work was carried out with the objective of evaluating the effects of acetic acid and establishing its threshold for alternative crops cultivated in wetland soils, such as maize, soybean and sorghum. Plants of maize (Embrapa BRS 1001) and sorghum (BRS 307) were exposed to six acetic acid levels, from zero to 8 mM; whereas plants of soybean (Embrapa BRS 133) were exposed to four levels, from zero to 4 mM. The experimental design used was completely randomized with six replications. Morphological parameters of plant root system (length, root radium, area and relative dry mass), relative shoot dry mass and N, P, K, Ca and Mg concentration in plant shoot were assessed. The acetic acid was toxic to maize, soybean and sorghum, being evidenced by decreases in the root length and dry mass, in the total plant dry mass and in the N, P, K, Ca and Mg contents in the plant shoot. The acetic acid concentrations responsible for decreasing 50% of the relative root length were 2 mM for soybean and 2.7 mM for maize and sorghum.
  • Authors:
    • Maul, J. E.
    • Buyer, J. S.
    • Austin, E. E.
    • Treonis, A. M.
    • Spicer, L.
    • Zasada, I. A.
  • Source: Applied Soil Ecology
  • Volume: 46
  • Issue: 1
  • Year: 2010
  • Summary: Soil microorganisms (bacteria, fungi) and microfauna (nematodes, protozoa) have been shown to be sensitive to organic amendments, but few experiments have investigated the responses of all these organisms simultaneously and across the soil profile. We investigated the impact of organic amendment and tillage on the soil food web at two depths in a field experiment. Over three growing seasons, field plots received seasonal organic amendment that was either incorporated into the soil (tilled) or not (no-till) as part of a tomato/soybean/corn cropping system. Un-amended, control plots that were either tilled or no-till were also included. We hypothesized that the addition of amendments would have a bottom-up effect on the soil food web, positively influencing the abundance of microorganisms, protozoa, and nematodes, primarily in the surface layers of the soil, but that this effect could be extended into deeper layers via tillage. Organic amendment had positive effects on most measured variables, including organic matter, respiration, protozoan and nematode density, and the abundance of PLFA biomarkers for bacteria and fungi. These effects were more pronounced in the 0-5 cm depth, but most variables increased with amendment in the deeper layer as well, especially with tillage. Denaturing Gradient Gel Electrophoresis (DGGE) of bacterial rDNA fragments indicated that distinct bacterial communities were selected for among tillage and amendment treatments and depths. Nematode faunal indices were not influenced by amendment, however. Increased nematode density in amended soils encompassed all trophic groups of free-living nematodes, with the greatest response among fungal-feeders, particularly with tillage. Increased biomass of microorganisms and decomposer microfauna in amended, tilled soils (0-5 cm depth) corresponded with a decline in the abundance of plant-parasitic nematodes. In control soils (0-5 cm depth), tillage reduced the relative abundance of fungal-feeding nematodes and increased the density of bacterial-feeding nematodes, in particular nematode species contributing to the Enrichment Index. When combined with organic amendment however, tillage was associated with increases in fungal-feeding nematodes and fungal biomarker PLFA. The results of this study suggest that when combined with amendment, tillage enhances the soil food web beyond the effect of amendment alone and is associated with declines in plant-parasitic nematodes.
  • Authors:
    • Li, G.
    • Luo, C.
    • Wang, X.
    • Niu, Y.
    • Gao, C.
    • Nan, Z.
    • Shen, Y.
    • Yang, J.
  • Source: Acta Prataculturae Sinica
  • Volume: 19
  • Issue: 1
  • Year: 2010
  • Summary: The effects of conventional tillage (t), conventional tillage with stubble retention (ts), no-tillage (nt), and no-tillage with stubble retention (nts) treatment on crop yield, soil total nitrogen and carbon, total organic carbon, oxidizible organic carbon, and carbon pool management index (CPMI) were investigated within a maize-wheat-soy rotation system in the western Loess Plateau. Total crop yield for ten harvests during the years 2001 to 2007 under ts and nts treatments increased by 3.63 and 1.62 g/kg compared with conventional tillage, but decreased by 2.48 g/kg on the nt treatment. Total nitrogen contents under nts treatment were 15.4%, 30.2% and 16.2% higher than t, ts and nt treatments. Total carbon under nts treatment was significantly increased by 2.04 g/kg and total organic carbon were 2.50, 1.56 and 1.70 g/kg higher than under t, ts and nt treatment, respectively. Easily oxidized organic carbon under nts was 2.13 g/kg higher than under t treatment. TN/TC decreased by 12.75%, 15.97%, 6.87% and 24.16% under t, ts, nt and nts treatments. The CPMI under ts, nt and nts were 12.6%, 20.1% and 46.6% higher than under t, both stubble retention and no-till were beneficial to increasing the soil organic carbon content and improving the quality of the carbon pool.
  • Authors:
    • Bagwan, N.
  • Source: International Journal of Plant Protection
  • Volume: 3
  • Issue: 2
  • Year: 2010
  • Summary: Crop root exudates of 20 crops like groundnut, soybean, pigeonpea, green gram, black gram, chickpea, pea, cowpea, mustard, cotton, castor, sunflower, safflower, sesamum, sorghum, pearl millet, maize, wheat, onion, and garlic were used in this study. Large variations of inhibitory effect of root exudates on S. rolfsii were observed. Low concentrations of root exudates (5% and 10%) had no effect on inhibition of mycelial growth and germination of sclerotia while, at high concentration (20%) inhibited the mycelial growth and germination of sclerotia. Mycelial growth, dry mycelium weight and sclerotial germination were recorded lowest in root exudates of sunflower, maize, pearl millet, sorghum, safflower, garlic, and onion. Mycelial growth, dry mycelium weight and sclerotial germination was recorded highest in root exudates of soybean, groundnut, green gram, black gram, pigeonpea, chickpea, pea and cowpea. It was observed that the root exudates of maize, sunflower and pearl millet showed a highest percentage of inhibition of mycelial growth and sclerotial germination. Another interesting of thing was observed that root exudates of groundnut, soybean and pea stimulate the mycelial growth and germination of sclerotia as compared to control. The results of this study suggested that the intercropping or crop rotation of safflower, maize, pearl millet, sorghum, sunflower, garlic, and onion with groundnut may be useful for the management of stem rot of groundnut and also for reduction of soil population of S. rolfsii in groundnut field. Similarly intercropping or crop rotation of soybean, green gram, black gram, chickpea, pea and cowpea with groundnut should be avoided. Based on these findings, it is hypothesized that root exudates of some crops contain antifungal compounds, while other stimulate the growth of fungal pathogens. Cultivation of safflower, maize, pearl millet and sorghum with groundnut could lead to a reduction in the occurrence of stem rot disease, especially when chemical control is not effective and economically costly. However, further investigation is necessary for isolation and identification of antifungal compounds in root exudates related to host-pathogen interaction.
  • Authors:
    • Cogo, N. P.
    • Paz Gonzalez, A.
    • Vidal Vazquez, E.
    • Bertol, I.
    • Luciano, R. V.
    • Fabian, E. L.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 34
  • Issue: 1
  • Year: 2010
  • Summary: Quantity and size distribution of sediments transported by runoff are influenced by soil management, cover and crop systems, and by rainfall, among other factors, representing an important aspect in soil conservation planning. The objective of this study was to quantify runoff sediments and relate them with runoff velocity, during soybean growth, in a simulated rainfall experiment initiated in 1998 on a typical Hapludox, under the following soil management systems: conventional tillage with one plowing plus two diskings (CT) and no-tillage on a never tilled soil with burned residues (NT). In these treatments, the rotation crop systems consisted of oat, soybean, vetch, corn, oats, bean, fodder radish, soybean, vetch, corn, and soybean. An additional treatment with bare soil with one plowing plus two diskings (BS) was also studied. Five simulated rainfall tests were applied to the treatments in the last soybean crop cycle, with an intensity of 63-67 mm h -1 for one hour, 24 h after a pre-wetting rainfall, with an intensity of 65 mm h -1 and long enough to initiate runoff. The sediments were quantified in runoff samples collected 10 minutes before the end of each simulated rainfall test, and were related with the runoff velocity. The sediment size in the runoff was influenced by soil management systems and the rainfall quantity. In the treatment without soil cover (BS), the quantity of coarse sediments was higher than in the treatments with cultivated soil, whereas in CT and NT treatments the quantity of fine-sized sediments was higher than in the BS treatment. More sediments tended to be transported in the runoff with the application of more rainfall events. The sediment quantity transported by runoff was related with the sediment size, fitting to a positive exponential model, while runoff velocity decreased exponentially with increased soil cover. The D 50 index was related with other variables, fitting to the potential model and increasing with runoff velocity.
  • Authors:
    • Singer, J.
    • Moorman, T.
    • Cambardella, C.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 87
  • Issue: 3
  • Year: 2010
  • Summary: Coupling winter small grain cover crops (CC) with manure (M) application may increase retention of manure nitrogen (N) in corn ( Zea mays L.), -soybean [ Glycine max (L.) Merr], cropping systems. The objective of this research was to quantify soil N changes after application of liquid swine M ( Sus scrofa L.) at target N rates of 112, 224, and 336 kg N ha -1 with and without a CC. A winter rye ( Secale cereale L.)-oat ( Avena sativa L.) CC was established prior to fall M injection. Surface soil (0-20 cm) inorganic N concentrations were quantified every week for up to 6 weeks after M application in 2005 and 2006. Soil profile (0-120 cm in 5, 20-cm depth increments) inorganic N, total N, total organic carbon and bulk density were quantified for each depth increment in the fall before M application and before the CC was killed the following spring. Surface soil inorganic N on the day of application averaged 318 mg N kg -1soil in 2005 and 186 mg N kg -1soil in 2006 and stabilized at 150 mg N kg -1soil in both years by mid-November. Surface soil NO 3-N concentrations in the M band were more than 30 times higher in the fall of 2005 than in 2006. The CC reduced surface soil NO 3-N concentrations after manure application by 32% and 67% in mid- November 2005 and 2006, respectively. Manure applied at 224 kg N ha -1 without a CC had significantly more soil profile inorganic-N (480 kg N ha -1) in the spring after M application than manured soils with a CC for the 112 (298 kg N ha -1) and 224 (281 kg N ha -1) N rates, and equivalent inorganic N to the 336 (433 kg N ha -1) N rate. These results quantify the potential for cover crops to enhance manure N retention and reduce N leaching potential in farming systems utilizing manure.
  • Authors:
    • Conte, O.
    • Trein, C. R.
    • Levien, R.
    • Debiasi, H.
    • Kamimura, K. M.
  • Source: PESQUISA AGROPECUARIA BRASILEIRA
  • Volume: 45
  • Issue: 6
  • Year: 2010
  • Summary: The objective of this work was to evaluate the effect of soil winter covers and soil mechanical loosening on soybean and corn yield, in no-tillage system. Two experiments were carried out in Rio Grande do Sul state, Brazil, in a compacted Argissolo Vermelho (Haplic Acrisol), in the 2005/2006 and 2006/2007 crop seasons. The first experiment was carried out in a complete block design, with a split plot arrangement. The treatments were two theoretical working depths of a driller chisel-type furrow opener (0.06 and 0.12 m, split plot), and three soil winter covers (main plot): fallow, black oat ( Avena strigosa), and black oat+common vetch ( Vicia sativa). In 2006, the soil cover black oat+common vetch was replaced by oilseed radish ( Raphanus sativus). In the second experiment, in a complete block design, the soil was chiseled and treatments consisted of black oat or oilseed radish as winter cover crops. Cover crops reduced soil superficial (0-0,06 m) compaction compared to fallow and, in the 2005/2006-crop season, under low water availability, provided higher soybean and corn yields. In the 2006/2007-crop season, when water availability was higher, the same did not happen. Increasing working depths of the chisel-type furrow opener did not affect soybean or corn yields. Soil chiseling reduced soybean and corn yields in comparison to the continuous no-tillage system.
  • Authors:
    • Eskandari, H.
    • Ghanbari, A.
  • Source: Notulae Scientia Biologicae
  • Volume: 2
  • Issue: 4
  • Year: 2010
  • Summary: An experiment was conducted in University of London, Kent, UK during the year 2003. The aim of experiment was to investigate the effects of planting pattern on performance of wheat and bean intercrops. A complete randomized block design with four replications was employed to compare the treatments. Treatments included wheat sole crop (W), Bean sole crop (B), within row intercropping (M 1), row intercropping (M 2) and mix cropping (M 3). The density of intercropping was according to replacement design (one wheat replaced by three bean plants). The results showed that total dry matter achieved by intercrops was significantly higher than those achieved by either wheat or bean sole crop. Regarding to weed control, intercrops were more effective than sole crops, especially bean sole crop. Crops performance in terms dry weight, height and percentage of leaf, stem pod and ear was affected by cropping systems depending on crop species, where wheat showed more changes compared to bean. Grain yield, harvest index and thousand grain weights of wheat were decreased in intercropping while bean had reduction only in grain yield.
  • Authors:
    • Eskandari, H.
    • Ghanbari, A.
  • Source: Notulae Scientia Biologicae
  • Volume: 2
  • Issue: 3
  • Year: 2010
  • Summary: Wheat ( Triticum aestivum) and bean ( Vicia faba L.) sole crops and their mixture in three planting pattern (M 1: alternate-row intercrop, M 2: within-row intercrop, M 3: mixed intercrop) were used to investigate the amount of resource consumption in terms of PAR interception and nutrient uptake. The experiment was carried out as randomized complete block design with four replications. The results showed that intercropping systems had a significant effect on environmental resources consumption, where intercropping systems had more nutrient uptake and light interception compared to sole crops, suggesting the complementarity effect of intercropping components in resources consumption. The ability of wheat and bean was different in intercropping systems in absorbing nutrients because of their differences in root morphology and cation exchange capacity.
  • Authors:
    • Chen, L.
    • Sun, Q.
    • Li, H.
    • Fang, S.
  • Source: Agroforestry Systems
  • Volume: 79
  • Issue: 2
  • Year: 2010
  • Summary: The importance of agroforestry systems in CO 2 mitigation has become recognized worldwide in recent years. However, little is known about carbon (C) sequestered in poplar intercropping systems. This study aims compare the effects of three poplar intercropping designs (configuration A: 250 trees ha -1; configuration B: 167 trees ha -1 and configuration C: 94 trees ha -1) and two intercropping systems (wheat-maize cropping system and wheat-soybean cropping system) on biomass production and C stocks in poplar intercropping systems. The experiment was conducted at Suqian Ecological Demonstration Garden of fast-growing poplar plantations in northwestern Jiangsu, China. A significant difference in C concentration was observed among the poplar biomass components investigated ( P≤0.05), with the highest value in stemwood and the lowest in fine roots, ranging from 459.9 to 526.7 g kg -1. There was also a significant difference in C concentration among the different crop components ( P≤0.05), and the highest concentration was observed in the maize ear. Over the 5-year period, the total poplar biomass increased with increasing tree density, ranging from 8.77 to 15.12 tonnes ha -1, while annual biomass production among the crops ranged from 4.69 to 16.58 tonnes ha -1 in the three configurations. Overall, total C stock in the poplar intercropping system was affected by configurations and cropping systems, and configuration A obtained the largest total C stock, reaching 16.7 tonnes C ha -1 for the wheat-soybean cropping system and 18.9 tonnes C ha -1 for the wheat-maize cropping system. Results from this case study suggest that configuration A was a relative optimum poplar intercropping system both for economic benefits and for C sequestration.