• Authors:
    • Diaz-Zorita, M.
    • Penon, E.
    • Coviella, C.
    • Ciocco, C.
    • Lopez, S.
  • Source: Spanish Journal of Agricultural Research
  • Volume: 6
  • Issue: 1
  • Year: 2008
  • Summary: Biological nitrogen fixation (BNF) is of key importance in the N balance of soybean ( Glycine max) crops. A number of authors have suggested that a negative balance may occur under high yield conditions. Few studies have measured the contribution of BNF to soil N in the pampas region. The aims of the present study were to compare three BNF determination methods - two isotopic methods using sorghum or a non-nodulating soybean isoline as a reference crop, and one involving the calculation of the difference in N content between the nodulating and non-nodulating soybean isolines - and to estimate the N balance in soybean crops raised under conventional tillage and no tillage practices. The study was performed in 2004-2005; a complete randomised block design was used with three replicates (plot dimensions 3*7 m). The different methodologies estimated BNF to account for 45-58% of total plant N, equivalent to 94 to 123 kg N ha -1. Depending on the methodology for estimating the BNF the soil N balance varied between -7 and 22 kg N ha -. With an average grain yield of 1,618 kg ha -1 and a BNF accounting for approximately 50% of total plant N (i.e., 115 kg N ha -1), the soil N balance was slightly positive (14 kg ha -1) and independent of the tillage practice. The tillage systems had no effect (P
  • Authors:
    • Durigan, J.
    • Correia, N.
  • Source: Bioscience Journal
  • Volume: 24
  • Issue: 4
  • Year: 2008
  • Summary: To evaluate the effect of cover crops [sorghum ( Sorghum bicolor 'Sara'), coverage sorghum ( S. bicolor * S. sudanensis 'Cober Exp'), forage millet ( Pennisetum americanum 'BN2'), common millet ( Pennisetum americanum), finger millet ( Eleusine coracana) and St. Lucia Grass ( Brachiaria brizantha)] and treatment with spontaneous vegetation, in soil fertility after two years under no-tillage systems, experiment was conducted at the farm 'Tres Marcos', Uberlandia, MG - Brazil. The soil was collected in February 2005, after the harvest of the soybean grains (cv. M-SOY 6101), in depths of 0-5 cm, 5-10 cm and 10-20 cm. The coverage resulted in soil chemical properties alteration, with different responses at the sampling depths studied. In first 5 cm of soil, was observed higher pH, organic matter, exchangeable Ca and Mg, base saturation, bases content and effective cation exchange capacity than in deeper samples. The soil kept with spontaneous vegetation showed the highest pH, Ca and Mg levels, base saturation and effective cation exchange capacity, while the soil under cover crop showed higher P and organic matter levels.
  • Authors:
    • Hons, F.
    • Wright, A.
    • Dou, F.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 39
  • Issue: 5/6
  • Year: 2008
  • Summary: Distribution of dissolved (DOC) and soil organic carbon (SOC) with depth may indicate soil and crop-management effects on subsurface soil C sequestration. The objectives of this study were to investigate impacts of conventional tillage (CT), no tillage (NT), and cropping sequence on the depth distribution of DOC, SOC, and total nitrogen (N) for a silty clay loam soil after 20 years of continuous sorghum cropping. Conventional tillage consisted of disking, chiseling, ridging, and residue incorporation into soil, while residues remained on the soil surface for NT. Soil was sampled from six depth intervals ranging from 0 to 105 cm. Tillage effects on DOC and total N were primarily observed at 0-5 cm, whereas cropping sequence effects were observed to 55 cm. Soil organic carbon (C) was higher under NT than CT at 0-5 cm but higher under CT for subsurface soils. Dissolved organic C, SOC, and total N were 37, 36, and 66%, respectively, greater under NT than CT at 0-5 cm, and 171, 659, and 837% greater at 0-5 than 80-105 cm. The DOC decreased with each depth increment and averaged 18% higher under a sorghum-wheat-soybean rotation than a continuous sorghum monoculture. Both SOC and total N were higher for sorghum-wheat-soybean than continuous sorghum from 0-55 cm. Conventional tillage increased SOC and DOC in subsurface soils for intensive crop rotations, indicating that assessment of C in subsurface soils may be important for determining effects of tillage practices and crop rotations on soil C sequestration.
  • Authors:
    • Sweeney, D.
    • Kelley, K.
  • Source: Crop Management
  • Issue: November
  • Year: 2008
  • Summary: Field studies were conducted from 1999 through 2004 in southeastern Kansas to evaluate the influence of tillage method [conventional (CT) and no-till (NT)], row spacing-population system (7.5-, 15-, and 30-inch rows planted at 225,000, 175,000, and 125,000 seeds/acre, respectively), and glyphosate application timing on soybean [ Glycine max (L.) Merr.] yield, weed control, and net economic returns. Herbicide treatments were: (i) preplant residual (pendimethalin) followed by glyphosate at 3 weeks after planting (WAP); (ii) glyphosate at 3 WAP; (iii) sequential glyphosate at 3 and 5 WAP; and (iv) glyphosate at 8 WAP. Soybean followed grain sorghum [ Sorghum bicolor (L.) Moench] in a 2-year rotation. Tillage method influenced yield very little. Narrower row spacing (7.5- and 15-inch) increased soybean yields 2 to 4 bu/acre in high-yielding environments compared to 30-inch rows and also provided greater weed control. Glyphosate applied sequentially (3 and 5 WAP) provided the highest weed control, but a single glyphosate application 3 WAP often produced the greatest net return, regardless of tillage or row spacing system. The results suggest that the adoption of NT planting will likely increase soybean net returns to a greater extent than reducing row spacing in the eastern Great Plains.
  • Authors:
    • Roel, A.
    • Terra, J.
    • Pravia, M.
  • Source: Proceedings of the 9th International Conference on Precision Agriculture, Denver, Colorado, USA, 20-23 July, 2008
  • Year: 2008
  • Summary: Soil management practices impacts on sorghum ( Sorghum bicolor) productivity have rarely been evaluated at field-scale. Field-scale soil management practices effects on sorghum grain yield were evaluated in three no-till crop-pasture rotation systems during two years in Uruguay (Oxyaquic Argiudoll). Treatments were established in a randomized complete block design in strips traversing the landscape in a sorghum-soyabean ( Glycine max) sequence integrated in three rotation systems: (1) continuous cropping (CC) with a winter cover crop of Lolium multiflorum; (2) short rotation (SR): two years pasture of T. pratense and L. multiflorum and two years of CC and; (3) long rotation (LR) four years pasture of Dactylis glomerata, Trifolium repens and Lotus corniculatus and two years of CC. Strips treatments included a factorial arrangement of two levels of cover crop residues (generated by winter grazing) with and without paraplough subsoiling. Strips were harvested with a combine equipped with a yield monitor. Data were analysed with mixed models accounting for spatial correlation. Yield was affected by year and rotation system but was not affected by management practices; either residue or subsoiling. Although its lower soil quality, CC had greater yield than SR and LR in 2006 (8.61 vs. 8.1 and 7.75 tonnes ha -1, respectively); however, no differences existed in 2007 (4.58 tonnes ha -1). Yield variations between field topographic zones were only found in 2007 SR (35%). Weak evidence of spatial correlation was found for soil properties at the site. No correlations were found between soil chemical properties and yield. Accounting for spatial correlation of 2006-2007 yields improved the statistical analysis. Animal treading and grazing did not appear to affect yield. For undegraded soils in temperate climates, cropping systems including no-tillage and perennial pastures preserved soil C, but did not guaranteed the same levels of grain productivity than more intensive cropping systems.
  • Authors:
    • Torbert, H.
    • Rogers, H.
    • Runion, G.
    • Prior, S.
  • Source: Journal of Plant Nutrition
  • Volume: 31
  • Issue: 4
  • Year: 2008
  • Summary: Increasing atmospheric CO 2 concentration could increase crop productivity and alter crop nutrient dynamics. This study was conducted (3 yrs) with two crops ([ Glycine max (L.) Merr.] and grain sorghum [ Sorghum bicolor (L.) Moench.]) grown under two CO 2 levels (ambient and twice ambient) using open top field chambers on a Blanton loamy sand under no-tillage. Macronutrient and micronutrient concentrations and contents were determined for grain, stover, and roots. Although elevated CO 2 tended to reduce nutrient concentrations, high CO 2 consistently increased nutrient content especially in grain tissue; this response pattern was more notable with macronutrients. The CO 2 effect was observed primarily in soybean. The consistent CO 2-induced increases in grain macronutrient contents favors reliable predictions of system outputs, however, predictions of crop nutrient inputs (i.e., stover and root contents) to the soil are less robust due to observed variability. Again, this is particularly true in regards to micronutrient dynamics in CO 2-enriched cropping systems.
  • Authors:
    • Chikte, P.
    • Bhalkare, S. K.
    • Thakare, S. M.
    • Lande, G. K.
  • Source: Journal Of Cotton Research And Development
  • Volume: 22
  • Issue: 2
  • Year: 2008
  • Summary: The experiment was conducted during the kharif season of 2004-05 at Dr. PDKV, Akola to evaluate the effect of different possible intercrops on bollworm complex on cotton crop. The intercrops viz., cotton+greengram, cotton+blackgram, cotton+cowpea, cotton+sorghum, cotton+maize, cotton+marigold, cotton+soybean in 1:1 ratio alongwith a treatment of sole cotton crop were sown. The intercrop cotton+cowpea proved to be the best recording least population of spotted bollworm, American bollworm and pink bollworm as against the treatment of sole cotton crop. The highest seed cotton yield of 251 kg/ha was recorded in cotton+cowpea-intercropping system as against 160 kg/ha recorded in the sole cotton crop.
  • Authors:
    • Rao, K. C.
    • Bharathi, V.
    • Reddy, L. K.
  • Source: International Journal of Agricultural Sciences
  • Volume: 4
  • Issue: 2
  • Year: 2008
  • Summary: Plant root exudates are known to affect survival, reproduction and development of various microorganisms in soil through extremely complex phenomenon. Saprophytic and pathogenic activities such as competition and antibiosis of the root microflora are mediated by exudates. An analysis of the effect of different crop root exudates such as groundnut, castor, soybean, sunflower, maize, green gram, hybrid sorghum and resistant pigeon pea revealed high inhibitory effect on conidial germination and radial growth of fusarium udum. In contrast, the root exudates of local sorghum varieties had less influence on the radial growth of antagonistic fungi viz., Penicillium sp., Trichoderma sp. Aspergillus sp. in the increasing order (6.8, 9.8 and 10 per cent), in spite of promoting germination and radial growth of the wilt pathogen Fusarium udum. However, root exudates of some crops such as groundnut, cotton, hybrid sorghum and resistant pipeaonpea had stimulatory effect on antagonistic fungi such as Aspergillus sp. Pencillium sp. and Trichoderma sp. in the range of 39.8 to 47.5 per cent. Root exudates of cotton were, however, found to promote both the wilt pathogen, as well as antagonistic fungi. Groundnut and castor exudates were found to be at par with each other in the promotion of radial growth of antagonists. Identification of such biochemical compounds in the crop root exudates responsible for inhibition or stimulation of the fungi would be more useful.
  • Authors:
    • Radford, B. J.
    • Yule, D. F.
    • McGarry, D.
    • Playford, C.
  • Source: Soil & Tillage Research
  • Volume: 97
  • Issue: 2
  • Year: 2007
  • Summary: Heavy wheel traffic causes soil compaction, which adversely affects crop production and may persist for several years. We applied known compaction forces to entire plots annually for 5 years, and then determined the duration of the adverse effects on the properties of a Vertisol and the performance of maize and sorghum crops under no-till dryland cropping with residue retention. For up to 5 years after a final treatment with a 10 Mg axle load on wet soil, soil shear strength at 70-100 mm and cone index at 180-360 mm were significantly ( P<0.05) higher than in a control treatment, and soil water storage and grain yield were lower. We conclude that compaction effects persisted because (1) there were insufficient wet-dry cycles to swell and shrink the entire compacted layer, (2) soil loosening by tillage was absent and (3) there were fewer earthworms in the compacted soil. Compaction of dry soil with 6 Mg had little effect at any time, indicating that by using wheel traffic only when the soil is dry, problems can be avoided. Unfortunately such a restriction is not always possible because sowing, tillage and harvest operations often need to be done when the soil is wet. A more generally applicable solution, which also ensures timely operations, is the permanent separation of wheel zones and crop zones in the field-the practice known as controlled traffic farming. Where a compacted layer already exists, even on a clay soil, management options to hasten repair should be considered, e.g. tillage, deep ripping, sowing a ley pasture or sowing crop species more effective at repairing compacted soil.
  • Authors:
    • Srinivasarao, C.
    • Vittal, K.
  • Source: Indian Journal of Fertilisers
  • Volume: 3
  • Issue: 5
  • Year: 2007
  • Summary: Soil samples from 21 locations of the All India Coordinated Research Project for Dryland Agriculture (AICRPDA) were characterized for organic carbon and availability of nutrients such as nitrogen, phosphorus, potassium, sulfur, Ca, Mg, Zn, Fe, Mn, Cu and B. These twenty one locations cover agro-ecological regions from 2.3 to 12.3, semiarid, and sub-humid climate, soils examined were Vertisols, Vertic sub-groups, Affisols, Inceptisols and Aridisols from different Indian states including Uttar Pradesh, Punjab, Jammu and Kashmir, Orissa, Jharkhand, Andhra Pradesh, Karnataka, Gujarat, Madhya Pradesh, Maharshtra, Tamil Nadu, Rajasthan, and Haryana. Representative soil profile samples from following production systems were collected: upland rice, groundnut, soyabeans, cotton,Rabi sorghum, pearlmillet, fingermillet and maize-based system. Rainfall ranged from 412 to 1378 mm among locations. Various physico-chemical properties of the 21 profiles indicated that most of the locations were low in organic carbon showing less than 0.5% organic C. Clay content varied widely among soil types. Low organic matter in these soils was one of the important factors contributing to low soil fertility. Except few locations, most of the soils were low in available N. Available P varied from low to very high. Available K and sulfur varied from low to high. Available Zn was below critical limit in Rajkot, Anatapur, Rewa, Akola, Bellary, Bijapur and Solapur, Agra, S.K. Nagar, Arjia, Hoshiarpur and Rakh Dhiansar. Iron was deficient in Rajkot, Bellary and Bijapur. Surface layers of several profiles were deficient in available Ca (<1.5 me 100/g) such as Phulbani, Anantapur, S.K. Nagar and Bangalore. Surface layers of soils at Phulbani, Ranchi, Anantapur, Agra, Hisar, S.K. Nagar, Bangalore, Arjia, Hoshiarpur and Rakh Dhiansar were Mg deficient (<1.0 me 100/g). Out of the 21 locations, 11 were boron deficient. Except Indore, all other soils were multinutrient deficient. Results suggest that dryland soils are multinutrient deficient, thus proper nutrient management strategies and soil water conservation practices in dryland agriculture are needed.