• Authors:
    • Van Remortel, R.
    • Smith, E.
    • Mehaffey, M.
  • Source: Ecological Applications
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: Meeting future biofuel targets set by the 2007 Energy Independence and Security Act (EISA) will require a substantial increase in production of corn. The Midwest, which has the highest overall crop production capacity, is likely to bear the brunt of the biofuel-driven changes. In this paper, we set forth a method for developing a possible future landscape and evaluate changes in practices and production between base year (BY) 2001 and biofuel target (BT) 2020. In our BT 2020 Midwest landscape, a total of 25 million acres (1 acre = 0.40 ha) of farmland was converted from rotational cropping to continuous corn. Several states across the Midwest had watersheds where continuous corn planting increased by more than 50%. The output from the Center for Agriculture and Rural Development (CARD) econometric model predicted that corn grain production would double. In our study we were able to get within 2% of this expected corn production. The greatest increases in corn production were in the Corn Belt as a result of conversion to continuous corn planting. In addition to changes to cropping practices as a result of biofuel initiatives we also found that urban growth would result in a loss of over 7 million acres of productive farmland by 2020. We demonstrate a method which successfully combines economic model output with gridded land cover data to create a spatially explicit detailed classification of the landscape across the Midwest. Understanding where changes are likely to take place on the landscape will enable the evaluation of trade-offs between economic benefits and ecosystem services allowing proactive conservation and sustainable production for human well-being into the future.
  • Authors:
    • Mariga, I. K.
    • Molatudi, R. L.
  • Source: African Journal of Agricultural Research
  • Volume: 7
  • Issue: 20
  • Year: 2012
  • Summary: An experiment was conducted under dryland conditions at the University of Limpopo experimental farm at Syferkuil in Capricorn district in 2007/2008 and 2008/2009 growing seasons to determine the effect of maize density and dry bean variety on maize/bean intercrop performance. The trial was at 2*2*2 factorial consisting of eight treatments: two maize densities (24 700 and 37 000 plants/ha), two dry bean varieties (small white haricot and red speckled sugar bean) and two cropping systems (sole cropping and intercropping). Open pollinated maize variety ZM 523 (ex CIMMYT) was used in the trial. The results showed that maize density of 24 700 plants/ha yielded lower maize grain than the recommended 37 000 plants/ha and maize grain yields in sole cropping were significantly higher than in intercropping in both growing seasons. Intercropping of maize with red speckled sugar bean resulted in lower grain yield than intercropping of maize with small white haricot in both seasons. Increasing maize density to 37 000 plants/ha reduced number of branches per plant and grain yield of dry bean in both seasons. Sole cropping produced the highest dry bean grain yield component values. Intercropping maize and beans was advantageous at the different bean variety x maize density combinations with all, except one, achieving Land equivalent ratio (LER) values greater than 1. Intercropping of maize plant density of 37 000 plants/ha with red speckled sugar bean gave the highest total LER value in 2007/8 season but less than 1 in 2008/9 season. Intercropping was more advantageous than sole cropping in this study. The highest monetary values were achieved by the bean sole crops and their intercrops with 24 700 plants/ha maize. In this study maize densities of 37 000 plants/ha and 24 700 plants/ha were found to be suitable for sole maize and maize/bean intercropping, respectively.
  • Authors:
    • Mkwinda, S.
    • Aune,J. B.
    • Ngwira, A. R.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Low crop yields due to continuous monocropping and deteriorating soil health in smallholder farmers' fields of sub-Saharan Africa have led to a quest for sustainable production practices with greater resource use efficiency. The aim of the study was to elucidate the short term effects of conservation agriculture (CA) systems on soil quality, crop productivity and profitability. In Balaka market and Ntonda sections of Manjawira Extension Planning Area (EPA), in Ntcheu district, central Malawi, we compared continuous monocropped maize (Zea mays) under conventional tillage practice (CP) with different CA systems in continuous monocropped maize (CAM) and intercropping with pigeonpea (Cajanus cajan) (CAMP), Mucuna pruriens (CAMM), and Lablab purpureus (L) (Sweet) (CAML). The study was conducted from 2008 to 2011 in 72 plots in 24 farmers' fields. In Balaka market section CA plots with maize + legumes produced up to 4.3 Mg ha(-1) of vegetative biomass against 3.5 Mg ha for maize alone in CP. In Ntonda section CA plots with maize + legumes produced up to 4.6 Mg ha(-1) of vegetative biomass against 2.4 Mg ha(-1) for maize alone in CP. In both sections, during the entire study period. CA did not have a negative effect on crop yields. During the drier seasons of 2009110 and 2010/11, CA had a positive effect on maize grain yield at both sites (average yield of 4.4 and 3.3 Mg ha(-1) in CA and CP respectively). However, associating maize with legumes reduced maize yields compared to CAM particularly in drier years of 2009-10 and 2010-11. Farmers spent at most 47 days ha(-1) producing maize under CA systems compared to 65 days ha(-1) spent under conventional tillage practices. However, total variable costs were higher in CA systems compared to conventional practice (at most US$416 versus US$344 ha(-1)). CAMP resulted in more than double gross margin compared to CPM (US$705 versus uS$344 hat). Infiltration estimated as time to pond was highest in CA maize legume intercrops (8.1 s) than CP (6.8 s). Although it was not feasible to directly estimate effects on water balances of these farmer-managed experiments, it can be assumed that the yield differences between CA and CP could be attributed to tillage and crop residue cover since other farm operations were generally the same. Intercropping maize and pigeonpea under CA presents a win-win scenario due to crop yield improvement and attractive economic returns provided future prices of maize and pigeonpea grain remain favourable. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Portela, S. I.
    • Andriulo, A. E.
    • Restovich, S. B.
  • Source: Field Crops Research
  • Volume: 128
  • Year: 2012
  • Summary: The agricultural system of the Humid Pampas consists of continuous cropping of soybean and maize under no tillage. This system may loose nitrogen (N) through leaching during the early and final stages of summer crops and during fallow. In this study (2005-2011) we evaluated the effect of fall-winter species (rescue grass, ryegrass, oats, barley, vetch, rape seed and forage radish) and a mixture of vetch and oats used as cover crops on water and N dynamics and main crop yield. Above-ground biomass production and N uptake by cover crops ranged from 1.1 to 11.9 Mg ha(-1) and from 17 to 223 kg N ha(-1), respectively, depending on sowing and killing dates and on the preceding crop. At killing, soil nitrate content in treatments with cover crops was 50-90% lower than in the control, reducing spring N leaching risk. When preceding maize, cover crops were killed in winter or early spring and their low C/N ratio (12-38) favored N release through residue decomposition. Vetch and rape seed as predecessors of fertilized maize increased residual N by approximate to 50 kg NO3-N compared to the control, posing the risk of fall N leaching. When preceding soybean, cover crops were killed in spring and, although their C/N ratios were higher (13-85), crucifers and legumes increased soil nitrate content. Maize yield was related to soil N availability at sowing (control and legumes > crucifers > grasses) which was inversely related to the preceding cover crop C/N ratio at killing. In normal to high rainfall years there were no differences in soybean yield among treatments. Water use by cover crops did not affect the main crop production except during an exceptionally dry year. Best synchronicity between N release from cover crop residues and harvest crop demand was achieved with the oats-vetch mixture before maize and with grasses before soybean. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • de Ridder, N.
    • Vanlauwe, B.
    • Pypers, P.
    • Guto, S. N.
    • Giller, K. E.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 1
  • Year: 2012
  • Summary: Soil fertility gradients develop on smallholder farms due to preferential allocation of inputs. A multi-location on-farm trial was conducted in Meru South, Central Kenya whose overall aim was to test minimum tillage and crop-residue retention practices in socio-ecological niches across heterogeneous smallholder farms. We identified three soil fertility classes together with the farmers, namely: good, medium, and poor. In each soil fertility class, two tillage (minimum or regular) and two crop residue (removed or retained) practices were tested for four consecutive seasons. Maize (Zea mays L.) grain yields in the good fields were above 2.5 Mg ha(-1) across cropping seasons and cumulated yields were not influenced by tillage or crop residue management. The grain yields in the medium fields ranged between 1.3 and 5.4 Mg ha(-1) and were greater with crop residue retention. In the poor fields, grain yield was
  • Authors:
    • Mullinix, B. G.,Jr.
    • Keeling, J. W.
    • Bordovsky, J. P.
    • Wheeler, T. A.
    • Woodward, J. E.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 7
  • Year: 2012
  • Summary: A field experiment was conducted under center-pivot irrigation in four wedges, with one wedge in continuous cotton (CC) and three wedges in a rotation (ROT) with 2 years cotton and 1 year in sorghum. Three irrigation rates (base = 1.0B, 1.5B, and 0.5B) were applied during 2007 to 2009 on a susceptible (ST) and partially resistant (PR) cultivar. Nitrogen applied during the season was proportional to irrigation rate. In the ROT wedges, 0.5B, 1.0B, and 1.5B irrigation and nitrogen rates averaged 1, 3, and 9% incidence of wilt, respectively. Disease incidence in the CC wedge averaged 6, 18, and 34% wilt incidence for 0.5B, 1.0B, and 1.5B irrigation and nitrogen rates. In the ROT wedges, the ST cultivar returned $143/ha more than the PR cultivars at the 0.5B irrigation and nitrogen rate whereas, at the 1.0B and 1.5B rates, the PR cultivars averaged $121 and $350/ha more than the ST cultivar. There was no significant irrigation and nitrogen or cultivar effect in the CC wedge on net value; however, trends were similar to the ROT wedge. Overall, ROT returned $285/ha more than CC, PR cultivars returned $123/ha more than the ST cultivar, and 1.0B returned $271 and $296/ha more than 0.5B and 1.5B rates, respectively. Microsclerotia density of V. dahliae averaged 2/cm(3) of soil in the ROT wedges and 23/cm(3) of soil in the CC wedge. Crop rotation, avoiding excessive irrigation, and using a partially resistant cultivar all reduced incidence of Verticillium wilt and improved net returns.
  • Authors:
    • Coquet, Y.
    • Justes, E.
    • Benoit, P.
    • Alletto, L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 153
  • Year: 2012
  • Summary: Water drainage and herbicide degradation and leaching were studied during four years in a continuous maize field managed with two tillage systems and two types of fallow periods. The tillage systems consisted of either a conventional practice with mouldboard ploughing (28 cm-depth) or a conservation practice with superficial tillage (
  • Authors:
    • Vogt, G. A.
    • da Veiga, M.
    • Balbinot Junior, A. A.
    • Spagnollo, E.
  • Source: Ciência Rural
  • Volume: 42
  • Issue: 3
  • Year: 2012
  • Summary: The objective of this study was to evaluate in the fifth year of experimentation, the effect of winter soil uses on residual straw on the soil, physical and chemical soil attributes and grain yield of common bean cultivated in succession. An experiment was carried out in the North Plateau of Santa Catarina State, Brazil, from May 2006 to April 2011. Five winter soil uses were investigated: 1) multicropping with black oat + ryegrass + common vetch without grazing (multicropping cover); 2) the same multicropping, with grazing and 100kg ha(-1) of nitrogen year(-1), applied during the growing period (pasture with N); 3) the same multicropping, with grazing and without nitrogen fertilization (pasture without N); 4) oil seed radish, without grazing (oil seed radish); and 5) natural vegetation, without grazing (fallow). In the fifth year of experimentation, multicropping cover treatment inputted greater straw on the soil, but it was not observed expressive differences in soil attributes among the five winter soil uses. Cover crops, annual pasture and winter fallow did not affect the grain yield of common bean cultivated in succession.
  • Authors:
    • Breland, T. A.
    • Bleken, M. A.
    • Bakken, L. R.
    • Lunde, H. W.
    • Borgen, S. K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 92
  • Issue: 3
  • Year: 2012
  • Summary: We applied a mechanistic ecosystem model to investigate the production and environmental performances of (1) current agricultural practice on two fields of a stockless organic cereal farm in southeast Norway and (2) alternative cereal-ley rotations and plowing time scenarios. Scenarios were simulated using historic weather data and a climate change scenario. Measured and simulated soil mineral N concentrations were generally low (1-4 g N m(-2)) and in good agreement. Simulated nitrate leaching was similar for the two fields, except when an extended period of black fallow weeding was practiced on one of them. Scenario simulations indicated that continuous cereal cropping undersown with a clover-grass winter cover crop performed best when evaluated by whole-rotation grain yield, the N yield/input-, and N loss/yield-ratios, and greenhouse gas emissions. However, the rotation had the largest soil organic matter losses. The N use and loss efficiency indicators were especially poor when ley years occurred consecutively and under fall plowing. Total greenhouse gas emissions were, however, smaller for the fall-plowed scenarios. In conclusion, our results indicated a modest potential for improving stockless systems by management changes in plowing time or crop rotation, which was hardly different in the climate change scenarios, although nitrate leaching increased substantially in the winter. Alternative strategies seem necessary to substantially improve the N-use efficiency in stockless organic grain production systems, e.g., biogas production from green manure and subsequent recycling of the digestate. Abandoning the stockless system and reintegrating livestock should also be considered.
  • Authors:
    • Tetu, T.
    • Lea, P. J.
    • Dubois, F.
    • Hirel, B.
  • Source: Sustainability
  • Volume: 3
  • Issue: 9
  • Year: 2011
  • Summary: In this review, we present the recent developments and future prospects of improving nitrogen use efficiency (NUE) in crops using various complementary approaches. These include conventional breeding and molecular genetics, in addition to alternative farming techniques based on no-till continuous cover cropping cultures and/or organic nitrogen (N) nutrition. Whatever the mode of N fertilization, an increased knowledge of the mechanisms controlling plant N economy is essential for improving NUE and for reducing excessive input of fertilizers, while maintaining an acceptable yield and sufficient profit margin for the farmers. Using plants grown under agronomic conditions, with different tillage conditions, in pure or associated cultures, at low and high N mineral fertilizer input, or using organic fertilization, it is now possible to develop further whole plant agronomic and physiological studies. These can be combined with gene, protein and metabolite profiling to build up a comprehensive picture depicting the different steps of N uptake, assimilation and recycling to produce either biomass in vegetative organs or proteins in storage organs. We provide a critical overview as to how our understanding of the agro-ecophysiological, physiological and molecular controls of N assimilation in crops, under varying environmental conditions, has been improved. We have used combined approaches, based on agronomic studies, whole plant physiology, quantitative genetics, forward and reverse genetics and the emerging systems biology. Long-term sustainability may require a gradual transition from synthetic N inputs to legume-based crop rotation, including continuous cover cropping systems, where these may be possible in certain areas of the world, depending on climatic conditions. Current knowledge and prospects for future agronomic development and application for breeding crops adapted to lower mineral fertilizer input and to alternative farming techniques are explored, whilst taking into account the constraints of both the current world economic situation and the environment.