• Authors:
    • Dare,Anne
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Authors:
    • Dold,Christian
    • Becker,Mathias
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 178
  • Issue: 4
  • Year: 2015
  • Summary: Lake Naivasha is a freshwater lake in the East African Rift Valley. With continued lake level declines between 1980 and 2011, the newly exposed land areas were gradually taken for agricultural use. The resulting chronosequences allow for an analysis of the effects of land use duration on nutrient dynamics and agricultural production. Transects representing land use durations of 0-30 (cropland) and 15-30 years (pasture) were established on soils formed on alluvial deposits and lacustrine sediments. We assessed changes in topsoil nitrogen (N) stocks (t ha(-1)), ammonium mineralization potential (N-supplying capacity), and plant-available P with increasing durations of land use. An additional greenhouse experiment studied the responses of kikuyu grass (Cenchrus clandestinus) and maize (Zea mays) in potted topsoil collected from differnt land-use types and chronosequence positions. With increasing duration of land use we noted a significant decline (P < 5%) in soil N contents under both pasture and cropland uses, following a model of exponential decay. The N stocks decreased at 84kgha(-1) a(-1) and a decay rate constant of 0.019a(-1) in pasture soil within 15 years, and at 75kgha(-1) a(-1) with a decay rate-constant of 0.013 a(-1) in cropland soil within 30 years. While the ammonium-N mineralization potential also decreased with land use duration, the trends were significant only in lacustrine pasture soils. Plant-available P did not show any trends that were related to the duration of land use. Kikuyu grass and maize accumulated less dry matter and N as the duration of use increased. This biomass accumulation was significantly related to soil N. A continued mineralization of soil organic matter has possibly contributed to the observed soil N depletion over time. The continuous agricultural use of the littoral wetland zone of Lake Naivasha is likely to entail declining production potentials for both pastures and food crops.
  • Authors:
    • Irani,S.
    • Majidi,M. M.
    • Mirlohi,A.
    • Zargar,M.
    • Karami,M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: The physiological basis of genetic variation in drought response and its association with forage yield and drought tolerance indices is not clear in sainfoin ( Onobrychis viciifolia Scop.). In this study, 100 sainfoin genotypes from 10 ecotypes were clonally propagated and evaluated under non-stressed and water deficit conditions during 2 yr. Physiological traits including chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content, proline content, relative water content (RWC), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) activity, dry matter yield (DMY), and stress tolerance index (STI) were studied. Large genotypic variation was observed among ecotypes for most of the studied traits indicating that selection in this germplasm would be useful. The results showed that water deficit greatly influenced physiological traits that affected forage production. Water deficit decreased DMY and RWC while significantly increasing carotenoid content, free proline content, CAT, APX, and SOD activity in both years. The relationship between dry matter yield and STI with proline content showed that ecotypes with high DMY and STI under water deficit conditions had higher proline accumulation in their leaves. With regard to the STI and principal component analysis (PCA), ecotypes Baft, Najafabad, and Sirjan were found to be drought tolerant or moderately drought tolerant. These ecotypes showed significantly higher values for proline content under water deficit conditions.
  • Authors:
    • Nash,R.
    • Motavalli,P.
    • Nelson,K.
    • Kremer,R.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Summary: Gaseous nitrogen (N) loss from denitrification and ammonia (NH3) volatilization from poorly drained soils in corn (Zea mays L.) production can be significant, diminish production, and lead farmers to apply a high rate of N. Nitrous oxide (N2O), a greenhouse gas that is emitted during denitrification, has a high global warming potential that contributes to climate change. Reducing gaseous N loss from poorly drained soils through drainage and N management in corn production is essential to minimizing the environmental impact and maintaining high yields. The objective of the study Was to determine how subsurface tile drainage and applications of polymer-coated urea (PCU) affect soil N2O emissions and N fertilizer-induced NH3 volatilization loss from a claypan soil. Drainage water management treatments consisted of conventional subsurface tile drainage, managed subsurface tile drainage, and no-drainage in combination with N fertilizer source (noncoated urea [NCU] and PCU). Subsurface drainage treatments did not significantly (p <= 0.05) affect cumulative soil N2O emissions and NH3 volatilization loss compared to no-drainage. Averaged over 2010 to 2013, cumulative soil N2O emissions from PCU was 2% of applied N, and NCU was 4% of applied N. Yield-scaled soil N2O emissions were reduced 53% with PCU compared to NCU. The percentage fertilizer loss from NH3 volatilization was significantly (p <= 0.05) reduced from 2.8% with NCU to 0.8% with PCU. These results suggest that use of PCU may assist in reducing cumulative losses of N2O and NH3 from poorly drained claypan soils, but drainage systems operating under this study's environmental conditions did not affect gaseous N losses.
  • Authors:
    • Panettieri,M.
    • Berns,A. E.
    • Knicker,H.
    • Murillo,J. M.
    • Madejon,E.
  • Source: Soil & Tillage Research
  • Volume: 151
  • Year: 2015
  • Summary: An augment of soil organic matter (SOM) in agricultural lands is mandatory to improve soil quality and fertility and to limit greenhouse gases emissions. A better protection of SOM from degradation is seconded to its inclusion in aggregates and to the formation of organo-mineral interactions with the clay fraction within the soil matrix. Under Mediterranean conditions, conservation agriculture (CA) has been widely related with macro-aggregates formation, SOM protection, and to an improvement of soil fertility and crop yields. The objective of this work was to evaluate the biogeochemical properties of five aggregate-size fractions obtained by dry sieving of a Calcic Fluvisol of an experimental farm managed under three different tillages. Soil aggregates distribution, total organic carbon (TOC), labile carbon pools, and enzymatic activities were measured in 2 different periods of the same agricultural campaign. CPMAS 13C NMR analyses were also performed to elucidate the structure of preserved SOM. The results evidenced seasonal variability in aggregate distribution, labile carbon pools and dehydrogenase activity (DHA), whereas TOC, permanganate oxidizable carbon (POxC), and beta- glucosidase activity demonstrated to be reliable soil quality indices for soil fractions. The NMR analyses showed a better SOM preservation under conservation tillages, due to higher plant litter inputs and/or higher amount of necromass derived compounds if compared with traditional tillage. Particularly interesting are the results of the O 0.5-1 mm fraction, in which different trends were found for beta-Glu and several organic compound classes if compared with the other fractions. Possibly, in this fraction are concentrated most of the products from cellulose depolymerization stabilized by organo-mineral interactions.
  • Authors:
    • Reynolds,W. D.
    • Drury,C. F.
    • Tan,C. S.
    • Yang,X. M.
  • Source: Nature
  • Volume: 95
  • Issue: 3
  • Year: 2015
  • Summary: The benefits of compost additions on soil organic carbon content and crop productivity are extant in the literature, but detailed studies of compost effects on soil physical quality (SPQ) are limited. The objective of this study was therefore to describe how one-time additions of compost impact the immediate, mid-term and long-term SPQ and crop yields of an agricultural soil. Food waste compost (FWC) was incorporated once into the top 10 cm of a humid-temperate Brookston clay loam soil at rates of 0 (Control), 75 dry t ha -1 (FWC-75), 150 dry t ha -1 (FWC-150) and 300 dry t ha -1 (FWC-300); measurements of SPQ parameters and corn yield were then made annually over the next 11 yr. The SPQ parameters included bulk density (BD), organic carbon content (OC), air capacity (AC), plant-available water capacity (PAWC), relative field capacity (RFC), and saturated hydraulic conductivity (K S), which were obtained from intact (undisturbed) soil core samples. Prior to compost addition, BD, OC, AC, PAWC, RFC and K S were substantially non-optimal, and BD had increased relative to virgin soil by 46%, while OC, AC and PAWC had decreased relative to virgin soil by 60, 56 and 43%, respectively. Improvements in SPQ 1 yr after compost addition were negligible or small for FWC-75 and FWC-150, but FWC-300 generated optimal values for BD, OC, AC, PAWC and RFC. The SPQ parameters degraded with time, but 11 yr after compost addition, OC and AC under FWC-300 were still within their optimal ranges, as well as significantly ( P<0.05) greater than the Control values by 65 and 26%, respectively. Soil cracks and biopores apparently induced substantial annual variation in K S, but average K S nevertheless increased with increasing compost addition rate. Corn grain yield varied substantially among years, which was likely due to weather and compost effects; however, 11-yr cumulative yields from the compost treatments were greater than the Control by 2200-6500 kg ha -1.
  • Authors:
    • Salazar,Osvaldo
    • Rojas,Claudia
    • Avendano,Fernando
    • Realini,Piero
    • Najera,Francisco
    • Tapia,Yasna
  • Source: Web Of Knowledge
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Vegetated buffer strips (BS) can help prevent nitrogen (N) losses from fields by subsurface lateral flow, thus protecting water resources. The purpose of this study was to determine if narrow BS would effectively remove dissolved inorganic N from subsurface lateral flow. Nitrate-N (NO3-N) and ammonia-N (NH3-N) concentrations in subsurface lateral flow were measured at 1 m depth in a BS system consisting of five treatments: G: strip of grass (Fescue arundinacea); GS: strip of grass and line of native shrubs (Fuchsia magellanica); GST1: strip of grass, line of shrubs and line of native trees 1 (Luma chequen); GST2: strip of grass, line of shrubs and line of native trees 2 (Drimys winteri); and C: bare soil as control. Water samples for the NO3-N and NH3-N measurements were collected between June 2012 and August 2014 in observation wells located at the inlet (input) and outlet (output) of each treatment. The analyses showed that vegetated BS had NO3-N removal efficiency ranging from 33 to 67 % (mean 52 %), with the G treatment showing the best performance in reducing NO3-N concentrations in subsurface lateral flow. The BS treatments were not effective in reducing NH3-N concentrations. The results suggested that N uptake by grass is the main process associated with the NO3-N retention capacity of vegetated BS.
  • Authors:
    • Sales,M. V. S.
    • Gama-Rodrigues,A. C.
    • Comerford,N. B.
    • Cropper,W. P.
    • Gama-Rodrigues,E. F.
    • Oliveira,P. H. G.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Respecification of structural models allows evaluating new hypothesis and enhances understanding of how changes in one pool can affect the other pools in the model. The aim of this study was to evaluate the theoretical concept of P pools (unmeasurable variables-latent) using data from Hedley's sequential extraction method for a better understanding of the P cycle in tropical soils. The theoretical concept being tested is the degree to which available P is controlled by different soil P pools as measured by extraction techniques. The respecified models were adequate and able to represent a generalization of P cycling in soils. The best structural model including latent variables with multiple indicators was consistent with the theoretical concept that the indicators of soil P pools are P fractions determined by the sequential extraction method. In this model, not only is there a direct relationship between the organic, occluded and primary mineral pools and the available P pool, but the indirect relationships via the organic pool were theoretically and statistically adequate. Thus, the model showed the interrelationships of geochemical and biological processes on the available P and it corroborated the hypothesis of the dependence of the available P pool to the organic pool in unfertilized tropical soils.
  • Authors:
    • Schlegel,A. J.
    • Assefa,Y.
    • Bond,H. D.
    • Wetter,S. M.
    • Stone,L. R.
  • Source: Web Of Knowledge
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Cattle ( Bos taurus) manure and swine ( Sus scrofa) effluent are applied to cropland to recycle nutrients, build soil quality, and increase crop productivity. The objective of this study was to determine the long-term effects of land application of cattle manure and swine effluent using the Kansas Nutrient Utilization Plan on crop yield, yield components, and crop nutrient uptake. The study was conducted for 10 yr (1999 through 2008) near Tribune, KS. There were 10 treatments: three levels of cattle manure and swine effluent (P, N, and 2N), three levels of N fertilizer (N 1=56, N 2=112, and N 3=168 kg N ha -1), and an untreated control. Corn ( Zea mays L.) grain and stover yields, yield components, and water use were measured. In all but 2 yr, all treatments significantly increased grain yield compared with the control and the lowest inorganic N rate. Mean corn grain yield over the years from the Cattle N and P, Swine N and P, and inorganic N 2 and N 3 treatments were about 2*, 1.8*, and 1.9* greater than the untreated control, respectively. Grain nutrient content and water productivity were consistently higher for the cattle manure treatments and the inorganic N 2 and N 3 treatments. However, grain yield and nutrient uptake did not differ among rates of cattle manure and swine effluent application. We concluded that using the lower application rate based on either N or P from the Kansas Nutrient Utilization Plan was sufficient to achieve optimal crop yield and water productivity.
  • Authors:
    • Siebers,M. H.
    • Yendrek,C. R.
    • Drag,D.
    • Locke,A. M.
    • Acosta,L. R.
    • Leakey,A. D. B.
    • Ainsworth,E. A.
    • Bernacchi,C. J.
    • Ort,D. R.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean ( Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6°C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis ( A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures.