• Authors:
    • Shanahan, J. F.
    • Adamchuk, V. I.
    • Kitchen, N. R.
    • Ferguson, R. B.
    • Roberts, D. F.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Integrating soil-based management zones (MZ) with crop-based active canopy sensors to direct spatially variable N applications has been proposed for improving N fertilizer management of corn ( Zea mays L.). Analyses are needed to evaluate relationships between canopy sensing and soil-based MZ and their combined potential to improve N management. The objectives of this study were to: (i) identify soil variables related to in-season crop canopy reflectance and yield and use these variables to delineate MZ for N fertilizer management; and (ii) compare corn yield response to different N fertilizer treatments for different MZ. Eight N rates (0-274 kg N ha -1 in 39 kg ha -1 increments) were applied in replicated small plots across six irrigated fields in 2007 to 2008 throughout central Nebraska. Soil variables evaluated for MZ delineation included: apparent soil electrical conductivity (EC a), soil optical reflectance, and landscape topography. Crop response to N was determined via active sensor assessments of in-season canopy reflectance (chlorophyll index, CI 590) and grain yield. Relationships between soil and topography data and crop performance were evaluated, with selected soil variables used to delineate two MZ within four of the six fields. Economic benefits to N application according to soil-based MZ were observed in fields with silty clay loam and silt loam soils with substantial relief and eroded slopes. Sensor-based algorithms may need to be adjusted according to MZ to account for differences in crop N response.
  • Authors:
    • Garcia-Torres, L.
    • Sanchez-Martin, L.
    • Sanz-Cobena, A.
    • Vallejo, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 149
  • Year: 2012
  • Summary: Urea has become the predominant source of synthetic nitrogen (N) fertilizer used throughout the world. Among the various available mitigation tools, urease inhibitors like NBPT have the most potential to improve efficiency of urea by reducing N losses, mainly via ammonia volatilization. However, there is a lack of information on the effect of N-(n-butyl) thiophosphoric triamide (NBPT) on other N losses such as gaseous emissions of N 2O and NO and NO 3- leaching. A two-year field experiment using irrigated maize ( Zea mays) crop was carried out under Mediterranean conditions to evaluate the effectiveness of urea coated with NBPT (0.4%, w/w) alone and with both NBPT and nitrification inhibitor dicyandiamide (DCD) (0.4 and 3%, w/w, respectively) to mitigate N 2O-N, NO-N and NO 3--N losses. The different treatments of U, U+NBPT and U+NBPT+DCD were applied to the maize crop in 2009 and then in 2010. The 2010 maize crop followed a fallow period, during which the 2009 crop residues were incorporated into the soil. Two different irrigation regimes were followed each year. In 2009, irrigation was controlled for the first 2 weeks following urea fertilization; whereas, the 2010 crop period was characterized by increased irrigation in the same period. After each treatment application, measurements of the changes in soil mineral N, gaseous emissions of N 2O and NO, nitrate leaching and biomass production were made. N 2O emissions were effectively abated by NBPT and NBPT+DCD and were reduced by 54 and 24%, respectively, in 2009. A reduction in nitrification rate by the inhibitors was also observed during 2009. In 2010 cropping period, NBPT reduced N 2O emissions by 4%; while the combination of NBPT and DCD treatment reduced N 2O emission by 43%. Yield-scaled N 2O emissions were reduced by 50 and 18% by NBPT and the mixture of NBPT+DCD, respectively, in 2009. Applying inhibitors did not have any significant effect on yield-scaled N 2O emissions in the 2010 crop period. Total NO losses from urea were 2.25 kg NO-N ha -1 in the 2009 crop period and 5 times lower in the following year; this may provide an indicator of the prevalence of nitrification as the main process in the production of N 2O in the 2009 maize crop. Most of the NO 3- was lost within the fallow period (i.e. 92, 81 and 75% of the total NO 3- leached for U, U+NBPT and U+NBPT+DCD, respectively), so the incorporation of crop residues was not as effective as expected at reducing these N losses. Our study suggests that the effectiveness of NBPT and combination of NBPT+DCD in reducing N losses from applied urea is influenced by management practices, such as irrigation, and climatic conditions.
  • Authors:
    • Akinnifesi, F. K.
    • Debusho, L. K.
    • Sileshi, G. W.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: Growing maize ( Zea mays L.) in association with legume trees in agroforestry arrangements has been shown to increase yields in many parts of sub-Saharan Africa; however, the stability of crop yields has not been critically analyzed in the various cropping systems that integrate leguminous trees. The objective of this analysis was to compare yield stability in improved cropping systems, namely maize-gliricidia [ Gliricidia sepium (Jacq.) Kunth] intercropping and fertilized monoculture maize, with the de facto practice of resource-poor farmers who grow maize continuously without any external input. Yield stability was determined for three long-term field trials (12-13 consecutive yr) conducted at Makoka Research Station in southern Malawi and Msekera Research Station in eastern Zambia. At Makoka, the most stable yield was recorded in maize-gliricidia intercrops. Average yield was highest for maize-gliricidia intercropping amended with 50% of the recommended N and P fertilizer, and this was comparable with the yield recorded in monoculture maize that received inorganic fertilizer. On the two sites at Msekera, the highest yield was recorded in fertilized monoculture maize, followed by maize-gliricidia intercrops. Yields were more stable, however, in maize-gliricidia intercropping than fertilized maize on both sites at Msekera. It was concluded that maize yields remain more stable in maize-gliricidia intercropping than in fertilized maize monoculture in the long term, although average yields may be higher with full fertilization.
  • Authors:
    • Cavigelli, M. A.
    • Spargo, J. T.
    • Mirsky, S. B.
    • Teasdale, J. R.
    • Maul, J. E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: There is interest in developing no-tillage systems for organic farming; however, potential limitations include the inability to control weeds and to provide sufficient crop available N. A 3-yr field experiment was conducted on organically certified land to explore roller-crimper technology for terminating a hairy vetch ( Vicia villosa Roth) cover crop in a reduced-tillage compared to a disk-tillage organic corn ( Zea mays L.) production system in Maryland. Within this tillage comparison, factors including the corn planting date and post-plant cultivation were examined for optimizing reduced-tillage organic corn production. Corn yield in roll-killed hairy vetch treatments where corn was planted by mid-June and that received high-residue cultivation was similar or higher than the best treatments with disk-killed hairy vetch. Delayed corn planting dates had little impact on corn yield in either disk- or roll-killed treatments, a result consistent with the similarity in weed biomass after cultivation, fertility, moisture, and radiation across planting dates. In 2 yr with supplemented weed populations, weed biomass was the major driver determining corn yield, which was reduced by 53 to 68% relative to weed-free control plots in the absence of post-plant cultivation, and by 21 to 28% with post-plant cultivation. In a year with low, natural weed populations, weeds had no significant influence on yield. These results demonstrate that organic corn production in a reduced-tillage roll-killed cover crop system can provide similar yields to those in a traditional tillage-based system, but also highlight the importance of maintaining low weed populations to optimize corn yield.
  • Authors:
    • Perales, H. R.
    • Martinez-Meyer, E.
    • Ureta, C.
    • Alvarez-Buylla, E. R.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 3
  • Year: 2012
  • Summary: Climate change is expected to be a significant threat to biodiversity, including crop diversity at centers of origin and diversification. As a way to avoid food scarcity in the future, it is important to have a better understanding of the possible impacts of climate change on crops. We evaluated these impacts on maize, one of the most important crops worldwide, and its wild relatives Tripsacum and Teocintes. Maize is the staple crop in Mexico and Mesoamerica, and there are currently about 59 described races in Mexico, which is considered its center of origin. In this study, we modeled the distribution of maize races and its wild relatives in Mexico for the present and for two time periods in the future (2030 and 2050), to identify the potentially most vulnerable taxa and geographic regions in the face of climate change. Bioclimatic distribution of crops has seldom been modeled, probably because social and cultural factors play an important role on crop suitability. Nonetheless, rainfall and temperature still represent a major influence on crop distribution pattern, particularly in rainfed crop systems under traditional agrotechnology. Such is the case of Mexican maize races and consequently, climate change impacts can be expected. Our findings generally show significant reductions of potential distribution areas by 2030 and 2050 in most cases. However, future projections of each race show contrasting responses to climatic scenarios. Several evaluated races show new potential distribution areas in the future, suggesting that proper management may favor diversity conservation. Modeled distributions of Tripsacum species and Teocintes indicate more severe impacts compared with maize races. Our projections lead to in situ and ex situ conservation recommended actions to guarantee the preservation of the genetic diversity of Mexican maize.
  • Authors:
    • Lindquist, J. L.
    • Drijber, R. A.
    • Bernards, M. L.
    • Francis, C. A.
    • Wortman, S. E.
  • Source: AGRONOMY JOURNAL
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: Previous studies have demonstrated benefits of individual cover crop species, but the value of diverse cover crop mixtures has received less attention. The objectives of this research were to determine the effects of spring-sown cover crop mixture diversity and mechanical cover crop termination method on cover crop and/or cash crop productivity, soil moisture and N, and profitability in an organic cropping system. An experiment was conducted between 2009 and 2011 near Mead, NE, where mixtures of two (2CC), four (4CC), six (6CC), and eight (8CC) cover crop species, or a summer annual weed mixture were included in a sunflower-soybean-corn rotation. Cover crops were terminated in late May using a field disk or sweep plow undercutter. Undercutting cover crops increased soil NO 3-N (0-20 cm) by 1.0 and 1.8 mg NO 3-N kg -1 relative to disk incorporation in 2010 and 2011, respectively. Cover crop mixtures often reduced soil moisture (0-8 cm) before main crop planting, though cover crop termination with the undercutter increased soil moisture content by as much as 0.024 cm 3 cm -3 compared to termination with the disk during early main crop growth. Crop yields were not influenced by cover crop mixture, but termination with the undercutter increased corn and soybean yield by as much as 1.40 and 0.88 Mg ha -1, respectively. Despite differences in productivity between spring cover crop mixtures and weed communities, crop yield was not different among these treatments; thus, profitability of the weed mixture-undercutter treatment combination was greatest due to reduced input costs.
  • Authors:
    • Lindquist, J. L.
    • Francis, C. A.
    • Wortman, S. E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Achieving agronomic and environmental benefits associated with cover crops often depends on reliable establishment of a highly productive cover crop community. The objective of this study was to determine if cover crop mixtures can increase productivity and stability compared to single species cover crops, and to identify those components most active in contributing to or detracting from mixture productivity. A rainfed field experiment was conducted near Mead, NE, in 2010 and 2011. Eight individual cover crop species (in either the Brassicaceae [mustard] or Fabaceae [legume] family) and four mixtures of these species (two, four, six, and eight species combinations) were broadcast planted and incorporated in late March and sampled in late May. Shoot dry weights were recorded for sole crops and individual species within all mixtures. Sole crops in the mustard family were twice as productive (2428 kg ha -1) as sole crops in the legume family (1216 kg ha -1), averaged across 2 yr. The land equivalent ratios (LERs) for all mixtures in 2011 were >1.0, indicating mixtures were more productive than the individual components grown as sole crops. Improved performance in mixture may be related to the ecological resilience of mixed species communities in response to extreme weather events, such as hail. Partial LERs of species in the mustard family were consistently greater than those in the legume family, indicating that mustards dominated the mixtures. Results provide the basis for yield-stability rankings of spring-sown cover crop species and mixtures for the western Corn Belt.
  • Authors:
    • Khizar, A.
    • Abbasi, M. K.
  • Source: Ecological Engineering
  • Volume: 39
  • Issue: February
  • Year: 2012
  • Summary: Application of organic amendments to soil is an important management strategy for enhancing the restoration of degraded soils and providing better soil conditions to below-ground soil microbial composition and above-ground plant community development. This study was conducted to investigate the effect of organic amendments (poultry manure - PM; white clover residues - WCR), a mineral N fertilizer (urea N - UN), or mixtures of these fertilizers on microbial activity and nitrogen (N) mineralization through both soil analysis (laboratory incubation) and aboveground maize (Zea mays L) growth (pot experiment). In the incubation experiment, soil was amended with PM, WCR, PM + WCR, UN, UN + PM, UN + WCR, and UN + PM + WCR at the rate equivalent to 200 mg N kg(-1) soil. Pot experiment was conducted in a glasshouse using same amendments to examine the response of maize seedlings to these treatments. Organic amendments and UN applied alone or in mixtures increased soil microbial biomass compared to the control. Among N amendments, the highest evaluation of CO2-C (47.7 mg kg(-1) day(-1)), microbial biomass C (434 mg kg) and microbial biomass N (86 mg kg(-1)) were recorded in the UN + PM + WCR while the lowest values were recorded in UN. It is estimated that 9-18% of the applied N had been assimilated into microbial N pool after 105 days. Mineralization of N was higher in the fertilized soil and ranged between 85 and 192 mg N kg(-1) compared with 46 mg N kg(-1) in the control. The net cumulative N mineralized (NCNM) ranged between 43 and 169 mg kg(-1) while the net cumulative N nitrified (NCNN) ranged between 16 and 69%. Combined application of UN + PM + WCR exhibited the highest NCNM and NCNN. On average, percentage conversion of added N into NO3--N was: 21% from organic sources, 40% from UN and 52% from UN + organic sources. The apparent recovery of added N (ANR) from PM, WCR and PM + WCR was 20, 24 and 45%, respectively, while UN, UN + PM, UN + WCR and UN + PM + WCR exhibited 50, 57, 64, and 73% ANR, respectively. Results obtained from the pot experiment (on maize) were consistent with the total mineral N (TMN) released from different amendments and highly significant correlations existed between TMN and plant dry matter yield (r(2) = 0.92) and TMN and N uptake of plants (r(2) = 0.89). The present study demonstrates the existence of substantial amount of N reserve present in organic substrates, which can be transformed into inorganic N pool and can be taken into account as potential sources in the management of the nutrient poor soils and crop growth. (C) 2011 Published by Elsevier B.V.
  • Authors:
    • Agus,Fahmuddin
    • Wahyunto
    • Al Dariah
    • Runtunuwu,Eleonora
    • Susanti,Erni
    • Supriatna,Wahyu
  • Source: Journal of Oil Palm Research
  • Volume: 24
  • Issue: August
  • Year: 2012
  • Summary: The peatlands of Indonesia are an increasingly important land resource for the livelihood of the people and for economic development, but they turn rapidly into a carbon source when the peat forests are cleared and drained. Therefore, strategies are needed for the sustainable management of the peatlands and to reduce greenhouse gas emissions. This research was conducted on 464 642 ha of peatland varying in depth between 200 and 680 cm, in the districts of Kubu Raya and Pontianak, in the West Kalimantan province of Indonesia. It was aimed at: (i) evaluating land use changes in the peatland of the two districts and assessing the CO2 emissions these entail; and (ii) recommending options for mitigation of the CO2 emissions. Satellite images in the years 1986, 2002 and 2008 were used for the evaluation of land use changes. This was followed by ground-truthing of recent land cover in 2009. Interviews were conducted with stakeholders to develop emission reduction strategies. The results show that the peatlands were used for various purposes, including the traditional slash-and-burn agriculture for maize, pineapple plantations, intensive vegetable farming, and rubber and oil palm plantations. The peat forest area decreased by 16% from 393 000 ha in 1986 to 329 390 ha in 2008, while shrubland increased by 153% from 9427 ha to 23 814 ha over the same period of time. Oil palm plantations and paddy fields also increased rapidly in expansion. The main sources of emissions were from peat burning, especially for the slash-and-burn farming, peat decomposition due to drainage, and the loss of biomass depending on the land use trajectories. Emission reduction can be achieved through various scenarios. Scenario I, confining future agricultural land development to peatland with peat of <3 m thick, is expected to reduce by 6.8 +/- 2.9% the 2010 to 2035 cumulative CO2 emissions from the 127 million tonnes 'business as usual' (BAU) level. Scenario II, providing fertiliser subsidy to replace the traditional burning technique in addition to Scenario I, is expected to reduce emissions by as much as 11.5 +/- 4.9%. Scenario III, switching future agricultural expansion to mineral soils, is expected to lower the cumulative emissions by as much as 20.5 +/- 8.8%. These scenarios form the basis for sustainable peatland management and for a state of preparedness to reduce emissions from peatland.
  • Authors:
    • Donkoh, S. A.
    • Amikuzino, J.
  • Source: African Crop Science Journal
  • Volume: 20
  • Issue: Suppl. 2
  • Year: 2012
  • Summary: Climate variability, the short-term fluctuations in average weather conditions and agriculture affect each other. Climate variability affects the agroecological and growing conditions of crops and livestock, and is recently believed to be the greatest impediment to the realisation of the first Millennium Development Goal of reducing poverty and food insecurity in arid and semi-arid regions of developing countries. Conversely, agriculture is a major contributor to climate variability and change by emitting greenhouse gases and reducing the agroecology's potential for carbon sequestration. What however, is the empirical evidence of this inter-dependence of climate variability and agriculture in Sub-Sahara Africa? In this paper, we provide some insight into the long run relationship between inter-annual variations in temperature and rainfall, and annual yields of the most important staple food crops in Northern Ghana. Applying pooled panel data of rainfall, temperature and yields of the selected crops from 1976 to 2010 to cointegration and Granger causality models, there is cogent evidence of cointegration between seasonal, total rainfall and crop yields; and causality from rainfall to crop yields in the Sudano-Guinea Savannah and Guinea Savannah zones of Northern Ghana. This suggests that inter-annual yields of the crops have been influenced by the total amounts of rainfall in the planting season. Temperature variability over the study period is however stationary, and is suspected to have minimal effect, if any, on crop yields. Overall, the results confirm the appropriateness of our attempt in modelling long-term relationships between the climate and crop yield variables.