• Authors:
    • Muchaonyerwa, P.
    • Chiduza, C.
    • Murungu, F. S.
  • Source: African Journal of Agricultural Research
  • Volume: 6
  • Issue: 24
  • Year: 2011
  • Summary: Use of legume cover crops has been reported to improve maize productivity through various mechanisms that include improved soil mineral N supply and weed control. However, in the smallholder irrigation farming sector, where maize is the staple crop, strategies for intercropping summer legume cover crops are often a challenge for farmers. Field experiments were conducted in a warm-temperate region of South Africa during the summer season of 2007/08 and 2008/09 to investigate the effects of strip intercropping patterns (3:2; 4:2 and 6:2 patterns) on the productivity of maize (cv. PAN 6479) together with mucuna or sunnhemp. The strip-intercrop patterns did not result in improved soil mineral N or weed control. Maize yields from rows adjacent to the cover crop strips were significantly (P
  • Authors:
    • Muthukrishnan, P.
    • Fanish, S. A.
  • Source: Madras Agricultural Journal
  • Volume: 98
  • Issue: 7/9
  • Year: 2011
  • Summary: Field experiment was conducted at farmer's field at Palani taluk of Dindigul district in Tamil Nadu during kharif 2008 with the objective of evaluating the drip fertigation on water saving and Water Use Efficiency (WUE) in intensive maize based intercropping system. The experiment was laid out in strip plot design with three replications. The experiment consisted of 9 fertigation levels in main plot and 4 intercrops in sub plot. Among the different fertigation levels, higher maize grain yield of 7300 kg ha-1 was recorded under drip fertigation of 100 per cent RDF with 50 per cent P and K through water soluble fertilizer (WSF) followed by application of 150 per cent RDF through drip (7050 kg ha -1). The yield increase over drip irrigation with soil application of fertilizer was 39 per cent. Drip irrigation helped to save water up to 43.65 per cent compared to surface irrigation method. Among the different intercrops tested, higher WUE of 21.0 kg ha -1 mm -1 was observed under maize+vegetable coriander intercropping system.
  • Authors:
    • Mutiibwa, D.
    • Irmak, S.
  • Source: Transactions of the American Society of Agricultural and Biological Engineers
  • Volume: 54
  • Issue: 1
  • Year: 2011
  • Summary: Canopy resistance (r c), which represents the composite diffusive resistance to water vapor transfer from vegetation surfaces to the atmosphere, plays an important role in describing the water vapor and energy fluxes and CO 2 exchange mechanisms and is an essential component of the complex ecophysiological and turbulent transport and evapotranspiration models. While one-step (direct) application of combination-based energy balance models (i.e., Penman-Monteith, PM) requires r c to solve for actual evapotranspiration (ET a), a remaining challenge in practical application of PM-type models is the scaling up of leaf-level stomatal resistance (r s) to r c to represent an integrated resistance from the plant community to quantify field-scale evaporative losses. We validated an integrated approach to scale up r s to the canopy. Through an extensive field campaign, we measured diurnal r s for a subsurface drip-irrigated soybean [ Glycine max (L.) Merr.] canopy and integrated several microclimatic and in-canopy radiation transfer parameters to scale up r s to r c. Using microclimatic and plant factors such as leaf area index for sunlit and shaded leaves, plant height, solar zenith angle, direct and diffuse radiation, and light extinction coefficient, we scaled up soybean r s as a primary function of measured photosynthetic photon flux density (PPFD). We assumed that PPFD is the primary and independent driver of r c; hence, the scaling approach relied heavily on measured PPFD-r s response curves. We present experimental verifications of scaled up r c by evaluating the performance of the scaled up r c values in estimating ET a. In addition, we solved the PM model on an hourly time step using the scaled up r c values and compared the PM-estimated ET a with the Bowen ratio energy balance system (BREBS)-measured ET a. The relationship between r s and PPFD was asymptotic, and r s showed strong dependence to PPFD, as PPFD alone explained 67% to 88% of the variability in r s. Beyond a certain amount of PPFD (400 to 500 mol m -2 s -1), r s became less responsive to PPFD. At smaller PPFD (0 to about 150 mol m -2 s -1) and greater r s (>70 to 80 s m -1) range, r s was very sensitive to PPFD. The r c_min, r c_avg, and r c_max ranged from 42 to 104 s m -1, 69 to 183 s m -1, and 95 to 261 s m -1, respectively, throughout the season. The seasonal average r c_min, r c_avg, and r c_max were 54, 92, and 129 s m -1, respectively. Canopy resistances were higher in early growing season during partial canopy closure, lower during mid-season, and high again in late season due to leaf aging and senescence. The ET a estimates from the PM model using scaled up r c values correlated very well with the BREBS-measured ET a. The average root mean square difference (RMSD) between the BREBS-measured and PM-estimated ET a was 0.08 mm h -1 (r 2=0.91; n=827), and estimates were within 3% of the measured ET a on an hourly basis. On a daily time step, RMSD was 0.64 mm d -1 (r 2=0.86; n=83), and the estimates were within 4% of the measured data. The approach successfully synthesized the whole-canopy resistance for use in PM-type combination-energy balance equations by scaling up from r s using a straightforward model of in-canopy radiation transfer.
  • Authors:
    • Gill, M. S.
    • Bhale, V. M.
    • Deshmukh, M. S.
    • Narkhede, W. N.
    • Gadade, G. D.
    • More, S. S.
  • Source: Indian Journal of Agronomy
  • Volume: 56
  • Issue: 2
  • Year: 2011
  • Summary: A field experiment was conducted for three consecutive years (2005-2007) at Parbhani to find out most productive and profitable cropping system. Among the different cropping systems, highest wheat [( Triticum aestivum L.) emend. Fiori & Paol] equivalent yield (19.9 t/ha) and net monetary returns (Rs 107.8*10 3/ha) were obtained from soybean [ Glycine max (L. Merr.)]-onion ( Allium capa L.) cropping system, followed by turmeric ( Curcuma domestica L.)+castor ( Ricinus communis L.) (WEY-14.0 t/ha, and NMR Rs 89.8*10 3/ha). The soybean-onion system also recorded maximum net monetary advantage per unit time (Rs 573/ha/day), employment (374 mandays) and water use efficiency (221 kg/ha-cm), followed by turmeric+castor intercropping system. The highest nutrient uptake was recorded in sorghum [ Sorghum bicolor (L.) Moench]-wheat followed by maize ( Zea mays L.)+cow-pea ( Vigna sinensis L.)-wheat and maize-wheat cropping systems. The highest soil nutrient status was observed in cotton ( Gossypium sp.)-summer groundnut ( Arachis hypogaea L.) followed by soybean-onion cropping systems.
  • Authors:
    • Stroosnijder, L.
    • Nyakudya, I. W.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 10
  • Year: 2011
  • Summary: Maize ( Zea mays L.), the dominant and staple food crop in Southern and Eastern Africa, is preferred to the drought-tolerant sorghum and pearl millet even in semi-arid areas. In semi-arid areas production of maize is constrained by droughts and poor rainfall distribution. The best way to grow crops in these areas is through irrigation, but limited areal extent, increasing water scarcity, and prohibitive development costs limit the feasibility of irrigation. Therefore, there is need for a policy shift towards other viable options. This paper presents daily rainfall analysis from Rushinga district, a semi-arid location in Northern Zimbabwe. The purpose of the rainfall analysis was to assess opportunities and limitations for rainfed maize production using 25 years of data. Data was analysed using a variety of statistical methods that include trend analysis, t-test for independent samples, rank-based frequency analysis, Spearman's correlation coefficient and Mann-Whitney's U test. The results showed no evidence of change in rainfall pattern. The mean seasonal rainfall was 631 mm with a standard deviation (SD) of 175 mm. December, January and February consistently remained the major rainfall months. The results depicted high inter-annual variability for both annual and seasonal rainfall totals, a high incidence of droughts ≥3 out of every 10 years and ≥1 wet year in 10 years. Using the planting criteria recommended in Zimbabwe, most of the plantings would occur from the third decade of November with the mode being the first decade of December. This predisposes the rainfall to high evaporation and runoff losses especially in December when the crop is still in its initial stage of growth. On average 5 to more than 20 days dry spells occupy 56% of the rainy season. Seasonal rainfall exhibited negative correlation ( P
  • Authors:
    • Odhiambo, L. O.
    • Irmak, S.
  • Source: Transactions of the American Society of Agricultural and Biological Engineers
  • Volume: 54
  • Issue: 3
  • Year: 2011
  • Summary: Estimation of actual evapotranspiration (ET), especially its partitioning into plant transpiration (T) and soil evaporation (E), in agricultural fields is important for effective soil water management and conservation and for understanding the interactions between ET, T and E with the management practices. Direct field measurements of ET, T, and E rates are difficult and costly; hence, mathematical models are used for estimating them. The objective of this study was to evaluate the practical applicability of the Shuttleworth-Wallace (S-W) model to estimate and partition ET in a subsurface drip-irrigated soybean ( Glycine max L. Merr.) field with partial residue cover. While its performance has been studied for various surfaces, the performance evaluation of the S-W model for such surface has not been carried out. An integrated approach of calculating bulk stomatal resistance (r sc) as a function of soil water content (theta i) was incorporated into the model to allow simulation of T over a range of theta i, and a residue decomposition function was introduced to account for surface residue decay over time to more accurately account for the actual residue cover in field conditions. The model performance was evaluated for different plant growth stages during the 2007 and 2008 growing seasons at the University of Nebraska-Lincoln, South Central Agricultural Laboratory near Clay Center, Nebraska. The sum of estimated T and E was compared to the bowen Ratio Energy Balance System (BREBS)-measured actual ET on a daily time-step. The model was able to capture the trends and magnitudes of measured ET, but its performance differed for various plant physiological growth stages. The root mean square difference (RMSD) values between the model-estimated and measured ET values for the growing season (day after emergence until physiological maturity) were 1.26 and 1.03 mm d -1 for 2007 and 2008, respectively. Best performance was observed during the mid-season during full canopy cover with a two-year average r 2 of 0.87, average RMSD of 0.94 mm d -1, and average mean biased error (MBE) of 0.30 mm d -1. Estimates for both initial and late season growth stages where E was dominant had the least agreement with BREBS measurements. The proportion of T and E in the estimated ET varied with growth stage. The S-W estimated seasonal total ET and BREBS measurements were equal in 2007 (S-W model ET=496 mm and BREBS ET=498 mm), and in 2008 the model underestimated by only 8.2% (S-W model ET=452 mm and BREBS ET=489 mm). While, in general, the model was successful in tracking the trends and magnitude of the BREBS-measured ET, further re-parameterization of the T module of the model can improve its accuracy to estimate ET, especially T, during the initial and late season (before full canopy cover and after physiological maturity) for a subsurface drip-irrigated soybean canopy. Other enhancements needed in the model for improved estimation of the E component include accurate determination of soil surface resistance coefficients and accounting for direct evaporation of intercepted rainfall on the canopy.
  • Authors:
    • Roskamp, G. K.
    • Glassman, K. R.
    • Ortiz-Ribbing, L. M.
    • Hallett, S. G.
  • Source: Plant Disease
  • Volume: 95
  • Issue: 4
  • Year: 2011
  • Summary: Common waterhemp ( Amaranthus rudis) and pigweeds ( Amaranthus spp.) are troublesome weeds in many cropping systems and have evolved resistance to several herbicides. Field trials to further develop Microsphaeropsis amaranthi and Phomopsis amaranthicola as bioherbicides for control of waterhemp and pigweeds were conducted to test the effectiveness of these organisms in irrigated and nonirrigated pumpkin and soybean plots over 2 years at three locations in western Illinois. The bioherbicide was applied with lecithin and vegetable oil at 187 liters ha -1 in 2008 and 374 liters ha -1 in 2009. Treatments included spore suspensions of M. amaranthi and P. amaranthicola alone, a mixture of both organisms, and sequential treatments of the organisms with halosulfuron-methyl (Sandea Herbicide) in pumpkin or glyphosate (Roundup Original Max Herbicide) in soybean. Bioherbicide effectiveness was estimated at approximately 7 and 14 days after treatment, as disease incidence, disease severity, percent weed control, and weed biomass reduction. Significant reductions in weed biomass occurred in treatments with one or both of the fungal organisms, and potential exists to tank mix M. amaranthi with halosulfuron-methyl. Leaf surface moisture and air temperatures following application may account for inconsistencies in field results between year and locations. These fungal organisms show potential as bioherbicides for weeds in the genus Amaranthus.
  • Authors:
    • Buzetti, S.
    • Bergamaschine, A. F.
    • Andreotti, M.
    • Pariz, C. M.
    • Costa, N. R.
    • Cavallini, M. C.
  • Source: Archivos de Zootecnia
  • Volume: 60
  • Issue: 232(1)
  • Year: 2011
  • Summary: We evaluated the effect of fertilization with 0, 50, 100 and 200 kg/ha of N, applied in each four growth intervals in the winter/spring season on dry matter yield in 30 days (DMY), leaf chlorophyll index (LCI) and total digestible nutrients (TDN), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin contents, and correlation equations of LCI with DMY and CP content in the marandu and ruziziensis grasses after intercrop arrangements with corn in Red Latosol (Oxisol) under irrigation. The major DMY occurred with photoperiod increasing, however, there were different responses to this attribute over of growth intervals, between and among the grasses with the N fertilization. In irrigated crop-livestock integration under savannah soil is technicality viable the cultivation of marandu and ruziziensis grasses, established by intercrop with corn at sowing or at the N fertilization. As even, in the N fertilization absence, produced satisfactory amounts of forage, with 1733 kg/ha (DMY), at the time of greatest scarcity of roughage to animals (winter/spring season). However, after the corn harvest, the N fertilization increase the DMY and improves the chemical composition, increasing the LCI, and CP and TDN contents, and decreasing NDF and ADF contents in the winter/spring season. The best correlation equations in function of LCI were logatithmica for DMY and potential for CP of the marandu grass and potential for both attributes of the ruziziensis grass.
  • Authors:
    • Pepo, P.
  • Source: Cereal Research Communications
  • Volume: 39
  • Issue: 1
  • Year: 2011
  • Summary: The interactions of ecological conditions, genotypes and agrotechnical elements determine the yield quantity, quality and stability in cereal (wheat, maize) production. The applied input-level can modify the adaptive capacity of crop models to ecological conditions. The effects of agrotechnical elements (crop rotation, fertilization, irrigation, crop protection, plant density) were studied in the long-term experiment on chernozem soil. Our scientific results proved that the high yields and good yield-stability were obtained in the input-intensive crop models, so these models had better adaptive capacity, high yield and resilience. Maize had lower ecological adaptive ability than winter wheat. The optimalization of agrotechnical elements reduces the harmful climatic effects so we can increase the yield and yield stability of cereals agro-ecosystems. The yields of wheat varied between 2 and 7 t ha -1 in extensive and 8 and 10 t ha -1 in intensive crop models and the yields of maize ranged between 2 and 11 t ha -1 and 10 and 15 t ha -1, respectively.
  • Authors:
    • Strickland, T. C.
    • Bosch, D. D.
    • Webster, T. M.
    • Truman, C. C.
    • Potter, T. L.
  • Source: Journal of Agricultural and Food Chemistry
  • Volume: 59
  • Issue: 14
  • Year: 2011
  • Summary: Intensive glyphosate use has contributed to the evolution and occurrence of glyphosate-resistant weeds that threaten production of many crops. Sustained use of this highly valued herbicide requires rotation and/or substitution of herbicides with different modes of action. Cotton growers have shown considerable interest in the protoporphyrinogen oxidase inhibitor, fomesafen. Following registration for cotton in 2008, use has increased rapidly. Environmental fate data in major use areas are needed to appropriately evaluate risks. Field-based rainfall simulation was used to evaluate fomesafen runoff potential with and without irrigation incorporation in a conventional tillage system (CT) and when conservation tillage (CsT) was practiced with and without cover crop residue rolling. Without irrigation incorporation, relatively high runoff, about 5% of applied, was measured from the CT system, indicating that this compound may present a runoff risk. Runoff was reduced by >50% when the herbicide was irrigation incorporated after application or when used with a CsT system. Data indicate that these practices should be implemented whenever possible to reduce fomesafen runoff risk. Results also raised concerns about leaching and potential groundwater contamination and crop injury due to rapid washoff from cover crop residues in CsT systems. Further work is needed to address these concerns.