• Authors:
    • Chen, J.
    • Burke, J.
  • Source: PLOS ONE
  • Volume: 10
  • Issue: 4
  • Year: 2015
  • Summary: Comparison of average crop yields with reported record yields has shown that major crops exhibit annual average yields three-to seven-fold lower than record yields because of unfavorable environments. The current study investigated the enhancement of pollen heat tolerance through expressing an Arabidopsis thaliana heat shock protein 101 (AtHSP101) that is not normally expressed in pollen but reported to play a crucial role in vegetative thermotolerance. The AtHSP101 construct under the control of the constitutive ocs/mas 'superpromoter' was transformed into cotton Coker 312 and tobacco SRI lines via Agrobacterium mediated transformation. Thermotolerance of pollen was evaluated by in vitro pollen germination studies. Comparing with those of wild type and transgenic null lines, pollen from AtHSP101 transgenic tobacco and cotton lines exhibited significantly higher germination rate and much greater pollen tube elongation under elevated temperatures or after a heat exposure. In addition, significant increases in boll set and seed numbers were also observed in transgenic cotton lines exposed to elevated day and night temperatures in both greenhouse and field studies. The results of this study suggest that enhancing heat tolerance of reproductive tissues in plant holds promise in the development of crops with improved yield production and yield sustainability in unfavorable environments.
  • Authors:
    • Stone, J. J.
    • Moriles-Miller, J.
    • Carlson, C. G.
    • Reicks, G.
    • Clay, D. E.
    • Clay, S. A.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Corn stover harvesting is a common practice in the western U.S. Corn Belt. This 5-yr study used isotopic source tracking to quantify the influence of two tillage systems, two corn ( Zea mays L.) surface residue removal rates, and two yield zones on soil organic C (SOC) gains and losses at three soil depths. Soil samples collected in 2008 and 2012 were used to determine 13C enrichment during SOC mineralization, the amount of initial SOC mineralized (SOC lost), and plant C retained in the soil (PCR incorp) and sequestered C (PCR incorp - SOC lost). The 30% residue soil cover after planting was achieved by the no-till and residue returned treatments and was not achieved by the chisel plow, residue removed treatment. In the 0- to 15-cm soil depth, the high yield zone had lower SOC loss (1.49 Mg ha -1) than the moderate yield zone (2.18 Mg ha -1), whereas in the 15- to 30-cm soil depth, SOC loss was higher in the 60% (1.38 Mg ha -1) than the 0% (0.82 Mg ha -1) residue removal treatment. When the 0- to 15- and 15- to 30-cm soil depths were combined, (i) 0.91 and 3.62 Mg SOC ha -1 were sequestered in the 60 and 0% residue removal treatments; (ii) 2.51 and 0.36 Mg SOC ha -1 were sequestered in the no-till and chisel plow treatments, and (iii) 1.16 and 1.65 Mg SOC ha -1 were sequestered in the moderate and high yield zone treatments, respectively. The surface treatments influenced C cycling in the 0- to 15- and 15- to 30-cm depths but did not influence SOC turnover in the 30- to 60-cm depth.
  • Authors:
    • Sheaffer, C. C.
    • Fernandez, A. L.
    • Wyse, D. L.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Field pea ( Pisum sativum L.) and lentil ( Lens culinaris Medik.) have potential as grain-producing legumes in organic rotations, but their yield is limited by weed competition. Intercropping can control weeds and increase total grain productivity per land area compared to sole cropping. A field experiment was conducted to investigate the effect of intercropping on field pea and lentil yields. Intercrop treatments were spring wheat ( Triticum aestivum L.), oat ( Avena sativa L.), and radish ( Raphanus sativus L.), which were harvested for grain; and winter rye ( Secale cereale L.) and rapid-cycling brassica ( Brassica campestris L.), which were not harvested. Intercropped lentil yields and total (lentil plus intercrop) yields were lower than or equal to weeded and unweeded sole cropped lentils in 5 of 6 site-years. Intercropped pea yields and total (pea plus intercrop) yields were lower than or equal to weeded and unweeded sole cropped pea in all site-years. Unharvested intercrops showed variable effectiveness at suppressing weeds. In lentil, winter rye intercropping reduced weed biomass compared to the unweeded control in 4 site-years, and rapid-cycling brassica reduced weed biomass in 2 site-years. In pea, winter rye, and rapid-cycling brassica treatments reduced weed biomass in all site-years. However, reductions in weed biomass were not associated with increases in grain yield. Estimated net returns to intercropping were variable, but generally similar for sole crops and intercrops on average. We did not observe consistent agronomic or economic advantages to the use of intercrops with field pea and lentil in the Minnesota environments studied.
  • Authors:
    • Franco,J. G.
    • King,S. R.
    • Masabni,J. G.
    • Volder,A.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 203
  • Year: 2015
  • Summary: In natural ecosystems, plant communities composed of functionally diverse species produce more biomass overall than less diverse communities. This increased biomass production is thought to occur due to complementary use of resources such as nutrients and water, and facilitation during sub-optimal environmental conditions. Using the same concept in a crop setting may lead to increased yield (overyielding) in diverse cropping systems when compared to monocultures. Different combinations of peanut, watermelon, okra, cowpea, and pepper planted alone or in various intercropping combinations were investigated over two growing seasons in a low-input system in the peak of summer heat in Texas. Each species was selected to perform a specific function within the system. Results from land equivalent ratio (LER) indicate that the within-row combination with peanut, watermelon and okra ( Wpwo) and peanut, watermelon, okra and cowpea ( Wpwoc) consistently overyielded in 2011 and 2012. LER values were 1.17 each for Wpwo and Wpwoc in 2011 and 1.17 and 1.20 in 2012, respectively. In 2011, watermelon was the dominant crop and was up-regulated in all intercropping combinations while all other component crops were down-regulated. Watermelon per plant production was significantly higher in the combination containing all species ( Wall) when compared to its monoculture, 5.50 and 2.09 kg fruit plant -1, respectively. In 2012, okra was the dominant crop and was up-regulated in all intercropping combinations while watermelon, cowpea, and pepper were down-regulated. Okra per plant production was significantly higher in Wpwoc and Wall than in monoculture, 2.28, 2.46, and 1.13 kg fruit plant -1, respectively. These findings suggest that three and four species intercropping combinations, whereby each crop is selected to perform a specific function within the system, may provide small-scale sustainably-minded producers a model system that can be utilized in suboptimal conditions and allow them to reduce inputs while increasing overall yields.
  • Authors:
    • Fransen, S.
    • Okwany, R. O.
    • Girma, K.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Managing the soil profile NO 3-N through crop selection and irrigation is an important consideration for the sustainable production of cellulosic biofuel feedstock crops. Data from two seasons were collected and analyzed from a 4-yr study conducted in Prosser, WA, to assess the effect of biofuel feedstock grasses and irrigation levels on soil profile NO 3-N. The experimental design was a split plot with three replications. The main plots had three irrigation levels (60, 80, and 100% evapotranspiration, ET), and the subplots contained three cultivars of switchgrass ( Panicum virgatum L.) and gamagrass ( Tripsacum dactyloides L.) cultivars. Soil and root samples were collected in fall 2011 (Season1) and winter of 2012 (Season2). Soil profile NO 3-N concentrations were highest at the lowest irrigation levels. In Season1, the soil profile NO 3-N concentration averaged over depths was 1.7 mg kg -1 for the switchgrass cultivars and 5.6 mg kg -1 for gamagrass. In Season2, the concentrations were 1.4 and 2.2 mg kg -1 for the switchgrass cultivars and gamagrass, respectively. We found a significant correlation between switchgrass root mass and soil profile NO 3-N; r=0.63-Kanlow; r=0.58-Blackwell; and r=0.46-Shawnee. Our results suggest that soil profile NO 3-N was lower under the switchgrass cultivars than gamagrass. More root mass and NO 3-N were accumulated at lower irrigation levels. The results reported here can help in developing practical decision tools for managing fertilizer N in biomass biofuel crops.
  • Authors:
    • Ngouajio, M.
    • Hayden, Z. D.
    • Brainard, D. C.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Mixtures of cereal rye ( Secale cereale L.) and the legume hairy vetch ( Vicia villosa Roth) are used to provide fixed N in balance with other important cover crop services, but late planting and interference from rye can limit vetch productivity. This 2-yr study in Michigan investigated how fall planting dates influence rye-vetch cover crop biomass quantity and quality in the spring, and evaluated whether staggering (delaying) rye seeding could improve vetch performance (biomass production, N fixation, and winter survival) in mixtures. Treatments consisted of a two-way factorial of three vetch planting dates (late August, mid-September, and late September) and three lengths of rye seeding stagger (co-seeded, short stagger, and long stagger). Later planting of co-seeded mixtures generally led to reduced total shoot biomass and lower proportions of vetch, resulting in cover crop residues with less vetch N and a higher total C/N. For earlier planting dates, delaying rye seeding until vetch emergence (short stagger) increased vetch shoot biomass by 760 to 1060 kg ha -1 (30-36 kg vetch N ha -1) relative to co-seeding. Staggered seeding provided no benefit to vetch biomass at later planting dates, and delaying rye seeding until the vetch three to four leaf stage (long stagger) reduced vetch winter survival by 12 to 42% compared with co-seeding. Additional research is needed to determine whether potential on-farm benefits of rye-vetch staggered seeding justify the additional management complexity involved and possible tradeoffs with other cover crop services.
  • Authors:
    • Sawyer, J. E.
    • Miguez, F.
    • Barker, D. W.
    • Mitchell, D. C.
    • Iqbal, J.
    • Pantoja, J.
    • Castellano, M. J.
  • Source: Web Of Knowledge
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Little information exists on the potential for N fertilizer application to corn ( Zea mays L.) to affect N 2O emissions during subsequent unfertilized crops in a rotation. To determine if N fertilizer application to corn affects N 2O emissions during subsequent crops in rotation, we measured N 2O emissions for 3 yr (2011-2013) in an Iowa, corn-soybean [ Glycine max (L.) Merr.] rotation with three N fertilizer rates applied to corn (0 kg N ha -1, the recommended rate of 135 kg N ha -1, and a high rate of 225 kg N ha -1); soybean received no N fertilizer. We further investigated the potential for a winter cereal rye ( Secale cereale L.) cover crop to interact with N fertilizer rate to affect N 2O emissions from both crops. The cover crop did not consistently affect N 2O emissions. Across all years and irrespective of cover crop, N fertilizer application above the recommended rate resulted in a 16% increase in mean N 2O flux rate during the corn phase of the rotation. In 2 of the 3 yr, N fertilizer application to corn (0-225 kg N ha -1) did not affect mean N 2O flux rates from the subsequent unfertilized soybean crop. However, in 1 yr after a drought, mean N 2O flux rates from the soybean crops that received 135 and 225 kg N ha -1 N application in the corn year were 35 and 70% higher than those from the soybean crop that received no N application in the corn year. Our results are consistent with previous studies demonstrating that cover crop effects on N 2O emissions are not easily generalizable. When N fertilizer affects N 2O emissions during a subsequent unfertilized crop, it will be important to determine if total fertilizer-induced N 2O emissions are altered or only spread across a greater period of time.
  • Authors:
    • Woodward, R.
    • Jones, M.
    • Stoller, J.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Spatial variation from soil and related factors often affects the outcome of agronomic field experiments. The randomized complete block (RCB) is the most prevalent design despite inefficiencies that can result in inflated error terms. Experimental designs such as the Latin square (LS) allow for bidirectional blocking and offer the potential to account for spatial variability better. The objectives of this research were to investigate the occurrence of two-way gradients in agronomic field trials and compare the estimated relative efficiency (ERE) of a LS to a RCB. Thirty LS trials were evaluated in 10 states during 2013 across the midwestern United States investigating crop yields of corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.], and sorghum [ Sorghum bicolor (L.) Moench]. The results show that 47% of the trials exhibited a two-way gradient, indicating this characteristic is widespread across a large geographic region. Overall, the ERE was increased in 70% of the trials by using the LS design. A lower ERE occurred in 7% of the trials conducted using a LS. Multiple gradients appear common in agronomic field plot trials and enough variation existed between the two blocking directions to justify the use of a LS design. Our data indicate the LS offers a low risk, high reward option of experimental design for controlling spatial heterogeneity and increasing precision. When possible, the LS design should be used in field experiments where the trial area appears uniform and gradients to block against are not obvious.
  • Authors:
    • Schaffer, B.
    • Munoz-Carpena, R.
    • Migliaccio, K. W.
    • Kisekka, I.
    • Khare,Y.
  • Source: Research Article
  • Volume: 29
  • Issue: 5
  • Year: 2015
  • Summary: In shallow water table-controlled environments, surface water management impacts groundwater table levels and soil water dynamics. The study goal was to simulate soil water dynamics in response to canal stage raises considering uncertainty in measured soil water content. Water and Agrochemicals in the soil, crop and Vadose Environment (WAVE) was applied to simulate unsaturated flow above a shallow aquifer. Global sensitivity analysis was performed to identify model input factors with the greatest influence on predicted soil water content. Nash-Sutcliffe increased and Root Mean Square Error reduced when uncertainties in measured data were considered in goodness-of-fit calculations using measurement probability distributions and probable asymmetric error boundaries, implying that appropriate model performance evaluation should be carried out using uncertainty ranges instead of single values. Although uncertainty in the experimental measured data limited evaluation of the absolute predictions by the model, WAVE was found a useful exploratory tool for estimating temporal variation in soil water content. Visual analysis of soil water content time series under proposed changes in canal stage management indicated that sites with land surface elevation of less than 2.0-m NGVD29 were predicted to periodically experience saturated conditions in the root zone and shortening of the growing season if canal stage is raised more than 9 cm and maintained at this level. The models developed could be combined with high-resolution digital elevation models in future studies to identify areas with the greatest risk of experiencing saturated root zone. The study also highlighted the need to incorporate measurement uncertainty when evaluating performance of unsaturated flow models.
  • Authors:
    • Freycon, V.
    • Laumonier, Y.
    • Locatelli, B.
    • Labriere, N.
    • Bernoux, M.
  • Source: Agricultural Journal
  • Volume: 203
  • Year: 2015
  • Summary: Healthy soils provide a wide range of ecosystem services. But soil erosion (one component of land degradation) jeopardizes the sustainable delivery of these services worldwide, and particularly in the humid tropics where erosion potential is high due to heavy rainfall. The Millennium Ecosystem Assessment pointed out the role of poor land-use and management choices in increasing land degradation. We hypothesized that land use has a limited influence on soil erosion provided vegetation cover is developed enough or good management practices are implemented. We systematically reviewed the literature to study how soil and vegetation management influence soil erosion control in the humid tropics. More than 3600 measurements of soil loss from 55 references covering 21 countries were compiled. Quantitative analysis of the collected data revealed that soil erosion in the humid tropics is dramatically concentrated in space (over landscape elements of bare soil) and time (e.g. during crop rotation). No land use is erosion-prone per se, but creation of bare soil elements in the landscape through particular land uses and other human activities (e.g. skid trails and logging roads) should be avoided as much as possible. Implementation of sound practices of soil and vegetation management (e.g. contour planting, no-till farming and use of vegetative buffer strips) can reduce erosion by up to 99%. With limited financial and technical means, natural resource managers and policy makers can therefore help decrease soil loss at a large scale by promoting wise management of highly erosion-prone landscape elements and enhancing the use of low-erosion-inducing practices.