• Authors:
    • Aragues, R.
    • Isidoro, D.
    • Barros, R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 155
  • Year: 2012
  • Summary: Nitrogen (N) pollution induced by irrigated agriculture is a significant environmental problem. The main N inputs and outputs were measured or estimated in the semi-arid La Violada irrigation district (Spain). Data on two periods (1995-1998 and 2006-2008) were compared and related to observed changes during the decade in cropping patterns and N fertilization and irrigation management. N fertilization exceeded crop N uptake due to over-fertilization of corn (426 kg N/ha in 1995-1998 and 332 kg N/ha in 2006-2008) and alfalfa (62 kg N/ha). Between the two periods, N fertilization decreased by 56%, primarily due to a change from corn to alfalfa and barley. Accordingly, N losses in the irrigation return flows (IRF) diminished from 31% of the applied fertilizer in 1995-1998 to 20% in 2006-2008. NO 3- concentrations and NO 3-N loads in the IRF decreased from 40 mg/L and 106 kg N/ha in 1995-1998 to 21 mg/L and 22 kg N/ha in 2006-2008, due to lower N fertilization, lower corn area and improved irrigation efficiency. N contamination in the IRF will be minimized by increasing the irrigation efficiency and decreasing the corn area and its N fertilization rates, particularly when supplemental organic N is applied at pre-sowing.
  • Authors:
    • Burke, I.
    • Snyder, A.
    • Pittmann, D.
    • Gallagher, R.
    • Koenig, R.
    • Borrelli, K.
    • Hoagland, L.
    • Fuerst, E.
  • Source: Journal of Sustainable Agriculture
  • Volume: 36
  • Issue: 4
  • Year: 2012
  • Summary: The nitrogen (N) dynamics of nine rotation systems designed to transition dryland cereal to organic production in eastern Washington State were examined. Systems combined cereal and legumes for grain, forage (FOR), and green manure (GRM). Few differences in N balances and soil inorganic N levels were found among transition systems when poor spring crop establishment resulted in competition from weeds. However, FOR and winter GRM crops produced adequate stands that were competitive with weeds and increased residual soil inorganic N in the final year of the transition. Winter legumes and continuous FOR systems demonstrated the greatest potential to provide a sustainable inorganic N source to subsequent organic cereal crops.
  • Authors:
    • Silva, S.
    • Stuchi, E.
    • Mourao Filho, F.
    • Cantuarias-Aviles, T.
    • Espinoza-Nunez, E.
    • Bremer Neto, H.
  • Source: Scientia Horticulturae
  • Volume: 142
  • Year: 2012
  • Summary: Despite considerable research conducted on 'Tahiti' lime [ Citrus latifolia (Yu Tanaka) Tanaka] in several countries, few long-term studies have focused on rootstock effects on fruit production and quality under non-irrigated conditions. As for many other fruit crops, rootstock studies for 'Tahiti' lime are often based on the evaluation of several horticultural responses simultaneously, instead of considering multivariate statistical approaches which may provide with more comprehensive information. Consequently, a trial was installed to evaluate the horticultural performance of non-irrigated 'Tahiti' lime trees budded onto the following 12 rootstocks: 'HRS 801' and 'HRS 827' hybrids; 'Rubidoux', 'FCAV' and 'Flying Dragon' trifoliates; 'Sun Chu Sha Kat' and 'Sunki' mandarins; 'Cravo Limeira' and 'Cravo FCAV' 'Rangpur' limes; 'Carrizo' citrange, 'Swingle' citrumelo, and 'Orlando' tangelo. The trial was installed in 2001, in an 8 m * 5 m spacing with no supplementary irrigation. Measurements of yield, fruit quality oriented to different consuming markets, canopy volume and tree tolerance to drought, were performed. A multivariate cluster analysis identified both 'Rangpur' lime rootstocks as those inducing larger cumulative yield and higher percentage of fruits for the domestic market, with highest drought tolerance to the trees. Despite of their high susceptibility to drought stress under non-irrigated conditions, the 'Flying Dragon' and 'FCAV' trifoliate rootstocks performed outstandingly for 'Tahiti' lime, inducing higher yield efficiency, early bearing and larger percentage of high-quality fruits for foreign markets, with smaller trees more suitable for high-density plantings.
  • Authors:
    • Liu, W. Z.
    • Li, Y.
    • Zhu, H. H.
    • Coleman, K.
    • Wu, J. S.
    • Guo, S. L.
  • Source: Plant and Soil
  • Volume: 353
  • Issue: 1/2
  • Year: 2012
  • Summary: Aims: Concerns over food security and global climate change require an improved understanding of how to achieve optimal crop yields whilst minimizing net greenhouse gas emissions from agriculture. In the semi-arid Loess Plateau region of China, as elsewhere, fertilizer nitrogen (N) inputs are necessary to increase yields and improve local food security. Methods: In a dryland annual cropping system, we evaluated the effects of N fertilizers on crop yield, its long-term impact on soil organic carbon (SOC) concentrations and stock sizes, and the distribution of carbon (C) within various aggregate-size fractions. A current version (RothC) of the Rothamsted model for the turnover of organic C in soil was used to simulate changes in SOC. Five N application rates [0 (N0), 45 (N45), 90 (N90), 135 (N135), and 180 (N180) kg N ha -1] were applied to plots for 25 years (1984-2009) on a loam soil (Cumulic Haplustoll) at the Changwu State Key Agro-Ecological Experimental Station, Shaanxi, China. Results: Crop yield varied with year, but increased over time in the fertilized plots. Average annual grain yields were 1.15, 2.46, 3.11, 3.49, and 3.55 Mg ha -1 with the increasing N application rates, respectively. Long-term N fertilizer application increased significantly ( P=0.041) SOC concentrations and stocks in the 0-20 cm horizon. Each kilogram of fertilizer N applied increased SOC by 0.51 kg in the top soil from 1984 to 2009. Using RothC, the calculated annual inputs of plant C (in roots, stubble, root exudates, etc.) to the soil were 0.61, 0.74, 0.78, 0.86, and 0.97 Mg Cha -1 year -1 in N0, N45, N90, N135 and N180 treatments, respectively. The modeled turnover time of SOC (excluding inert organic C) in the continuous wheat cropping system was 26 years. The SOC accumulation rate was calculated to be 40.0, 48.0, 68.0, and 100.0 kg C ha -1 year -1 for the N45, N90, N135 and N180 treatments over 25 years, respectively. As aboveground biomass was removed, the increases in SOC stocks with higher N application are attributed to increased inputs of root biomass and root exudates. Increasing N application rates significantly improved C concentrations in the macroaggregate fractions (>1 mm). Conclusions: Applying N fertilizer is a sustainable practice, especially in carbon sequestration and crop productivity, for the semiarid Loess Plateau region.
  • Authors:
    • Abraham, S.
    • Babar, S.
    • Singh, J.
    • Majumdar, G.
    • Venugopalan, M. V.
  • Source: Better Crops with Plant Food
  • Volume: 96
  • Issue: 2
  • Year: 2012
  • Summary: Despite large tracts of irrigated cotton, rainfed systems remain the most important option for improving cotton production in India. Within rainfed fields, the potential effects of adopting high plant population with adequate NPK fertilizer management offer a good opportunity to increase crop productivity.
  • Authors:
    • Thomashow, L. S.
    • Paulitz, T. C.
    • Kwak, Y. S.
    • Bonsall, R. F.
    • Parejko, J. A.
    • Mavrodi, O. V.
    • Mavrodi, D. V.
    • Weller, D. M.
  • Source: Applied and Environmental Microbiology
  • Volume: 78
  • Issue: 3
  • Year: 2012
  • Summary: Natural antibiotics are thought to function in the defense, fitness, competitiveness, biocontrol activity, communication, and gene regulation of microorganisms. However, the scale and quantitative aspects of antibiotic production in natural settings are poorly understood. We addressed these fundamental questions by assessing the geographic distribution of indigenous phenazine-producing (Phz +) Pseudomonas spp. and the accumulation of the broad-spectrum antibiotic phenazine-1-carboxylic acid (PCA) in the rhizosphere of wheat grown in the low-precipitation zone (
  • Authors:
    • Assefa, Y.
    • Roozeboom, K. L.
    • Staggenborg, S. A.
    • Du, J.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 2
  • Year: 2012
  • Summary: Corn ( Zea mays L.) yield has increased from about 1.5 Mg ha -1 in the early 1900s to 8.5 Mg ha -1 in the beginning of the 2000s in the United States. Information about yield and management changes in irrigated and dryland corn yields for the hybrid era is scarce. The objective of the present study was to determine the magnitude of yield and management changes in irrigated and dryland corn from 1939 through 2009. Data from selected irrigated and dryland corn performance trials conducted in Kansas from 1939 through 2009 were analyzed. On average, corn yields have increased at rate of 90 kg ha -1 yr -1 in dryland and 120 kg ha -1 yr -1 in irrigated trials. Corn yield changes from one decade to another were not similar for the seven decades considered. Both irrigated and dryland yields increased significantly at least every two decades until the last three, during which dryland yields stagnated. Changes in hybrid technology and changes in crop management factors, such as a decrease in planting and harvesting date by about a quarter of a day yr -1, increased planting density at the rate of 597 plants ha -1 yr -1, and increased N and P fertilizer rates by 2.6 and 0.40 kg ha -1 yr -1, respectively, were found for the same time period in dryland corn. In addition, climate changes contributed to yield increases in the past through increased total rainfall, average monthly minimum and maximum temperature in March, and decreased maximum temperature from July through September.
  • Authors:
    • Calderón, F. J.
    • Vigil, M. F.
    • Nielsen, D. C.
    • Benjamin, J. G.
    • Poss, D. J.
  • Source: Field Crops Research
  • Volume: 125
  • Year: 2012
  • Summary: Grasspea (GP) (Lathyrus sativus) is a drought-tolerant legume that can be grown for forage and grain. It has potential value to be used as a nitrogen-fixing crop in dryland rotations with non-legume grain crops. However, the agronomy of GP for the Central Great Plains region have not been investigated. The objective of this research was to compare the grain and biomass yield, as well as N accumulation of GP relative to field pea (FP) in two planting configurations. We carried out a 3-year field experiment to compare dryland GP with Admiral yellow field pea (Pisum sativum) in two configurations: (1) a wide row spacing with lower population (WL) with 76-cm rows with 75 kg seeds planted per ha, and (2) a narrower row spacing with a higher population (NH) with 19-cm rows with 136 kg seeds planted per ha. We measured the biomass, grain yield. N content, and soil water use. Our results show that the NH treatment out-yielded the WL treatment in both pea species. The GP had higher yield then FP on the lowest yielding year, while FP yielded better when overall yields were higher. Biomass production was also higher for the NH configuration, and GP was a higher biomass producer than FP over the 3-year study. The GP had higher N concentration in shoots and seed compared to FP, indicating higher N-fixing capacity. The FP matured faster than GP, and had marginally higher grain water use efficiency than GP. Our results show that GP is a viable alternative legume for the Central Great Plains, with comparable yields in low precipitation years. However, the longer growing season required by GP to mature has water use implications in years with reduced water availability in mid to late summer.
  • Authors:
    • Hansen, N. C.
    • Allen, B. L.
    • Baumhardt, R. L.
    • Lyon, D. J.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: The Great Plains region of the United States is an area of widespread dryland crop production, with wheat being the dominant crop. Precipitation in the region ranges from 300 to 500 mm annually, with the majority of precipitation falling during hot summer months. The prevailing cropping system is a two-year rotation of wheat and summer fallow. The adoption of no-till practices has resulted in greater precipitation storage and use efficiency, which has led to greater cropping intensity, higher productivity, more diverse crop rotations, and improvements in soil properties. In Colorado, for example, a no-till rotation of winter wheat-maize-fallow increased total annualized grain yield by 75% compared to winter wheat-summer fallow. Soil erosion was reduced to just 25% of that from a conventional tillage wheat-summer fallow system. The primary challenge with reducing fallow frequency is the increase in yield variability and risk of crop failure. Improved approaches for choosing crop or fallow are being developed based on soil water content and forecasted weather. Development of alternative crops, crop rotations, and integrated livestock systems that are sustainable from both economic and ecological perspectives is an on-going effort. Other research is addressing adaptation of cropping practices to climate change and the potential for dryland biomass crop production for the developing biofuel industry.
  • Authors:
    • Barbarick, K. A.
    • Ippolito, J. A.
    • McDaniel, J.
    • Hansen, N. C.
    • Peterson, G. A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 150
  • Year: 2012
  • Summary: Dryland agroecosystems are generally ideal environments for recycling biosolids. However, what is the efficacy of biosolids addition to a no-till dryland management agroecosystem? From 2000 to 2010, we studied application of biosolids from the Littleton/Englewood, CO Wastewater Treatment Plant versus commercial N fertilizer in dryland no-till wheat ( Triticum aestivum, L.)-fallow (WF) and wheat-corn ( Zea mays, L.)-fallow (WCF) rotations at a site approximately 40 km east of Byers, CO. We tested if biosolids would produce the same yields and grain P, Zn, and Ba concentrations as an equivalent rate of N fertilizer, that biosolids-borne P, Zn, and Ba would not migrate below the 10 cm soil depth, and that biosolids application would result in the same quantity of residual NO 3-N as the equivalent N fertilizer rate. Biosolids and N fertilizer produced similar wheat and corn yields; but, biosolids application resulted in smaller wheat grain Ba due to the soil formation of BaSO 4. Biosolids application produced greater NO 3-N concentrations than N fertilizer in the 30-60 and 60-90 cm depths for the WF rotation and all but the 5-10 and 120-150 cm depths for the WCF rotation. We concluded that biosolids application in a no-till managed dryland agroecosystem is an efficacious method of recycling this nutrient source.