• Authors:
    • Kohl, D. H.
    • Shearer, G.
    • Lockeretz, W.
  • Source: Science
  • Volume: 211
  • Issue: 4482
  • Year: 1981
  • Summary: A small minority of farmers in the Midwest produces crops on a commercial scale without using modern fertilizers and pesticides. On the basis of a 5-year study, it appears that these farmers have more in common with the majority of farmers in the region than with certain stereotypes of organic farmers. Their farming practices (other than chemical use), the size and labor requirements of their farms, and the production and profitability they achieve differ from those of conventional farmers by considerably less than might be expected on the basis of the fundamental importance of chemicals in modern agricultural production. Compared to conventional methods, organic methods consume less fossil energy and cause less soil erosion, but have mixed effects on soil nutrient status and grain protein content.
  • Authors:
    • Blackmer, A. M.
    • Breitenbeck, G. A.
    • Bremner, J. M.
  • Source: Journal of Environmental Quality
  • Volume: 10
  • Issue: 1
  • Year: 1981
  • Summary: A simple method was developed for accurate injection of anhydrous ammonia in field studies to assess the effects of this fertilizer on emissions of nitrous oxide (N2O) from soils. Use of this method and of a chamber technique for measurement of N2O emissions showed that fertilization of three Iowa soils with anhydrous ammonia (250 kg N/ha) led to a very marked increase in emission of N2O. Emissions of N2O-N from the fertilized soils in 139 days ranged from 12.1 to 19.6 kg/ha and averaged 15.6 kg/ha. The corresponding emissions from the unfertilized soils ranged from 1.7 to 2.5 kg/ha and averaged 2.0 kg/ha. Most of the N2O evolved from the fertilized soils was produced within 42 days after fertilization, and N2O emissions from these soils 96 days after fertilization were not appreciably greater than those from the corresponding unfertilized soils. The fertilizer-induced emissions of N2O-N observed after application of anhydrous ammonia greatly exceeded those detected in similar field studies using other N fertilizers and represented 4.0-6.8% of the fertilizer N applied.
  • Authors:
    • Singh, J. S.
    • Sims, P. L.
  • Source: Journal of Ecology
  • Volume: 66
  • Issue: 2
  • Year: 1978
  • Summary: (1) Intra-seasonal dynamics of the various above-ground and below-ground primary producer compartments for ten central and western North American grassland sites are presented. (2) The seasonal peak values of the primary producer compartments are examined, as indicative of the net accumulation of organic material, and the relationships of these peak values to various abiotic regimes at the sites are investigated. (3) Seasonal live biomass followed either a unimodal or a bimodal growth pattern. In general, grasslands with only cool-season or only warm-season plants showed a unimodal pattern, while grasslands dominated by both cool- and warm-season species had a bimodal seasonal growth pattern. There were no significant differences between grazed and ungrazed treatments in seasonal live biomass, although there was a significant site x treatment interaction. (4) Peak live biomass ranged from 84 to 336 g m-2, and showed a linear increase with increasing amounts of growing-season precipitation up to 450 mm; at higher values of precipitation increases in live biomass tended to level out. (5) Maximum rates of accumulation of live biomass ranged from 0-4 to 6-5 g m-2 day-1 . Ungrazed grasslands had a peak rate of 4-2 g m-2 day-1 compared with 3-2 g m-2 day-1 for grazed grasslands. (6) Generally the recent-dead compartment showed maximum values soon after the peak in the live compartment. Material in the old-dead compartment, however, was at a maximum early in the growing season, and a general decline in the standing crop of old dead material followed as material was transferred to the litter compartment. (7) Litter dynamics responded closely to precipitation events, and showed a rather erratic pattern. (8) Root biomass generally reached a maximum about midway through the growing season. On the cooler grasslands, grazed treatments typically had a larger peak in root biomass; in contrast, the warmer grasslands did not show a marked response in root biomass to grazing.
  • Authors:
    • Moore, R. A.
    • Krueger, C. R.
    • White, E. M.
  • Source: Agronomy Journal
  • Volume: 68
  • Issue: 4
  • Year: 1976
  • Summary: Cultivated Williams loam (Typic Argiboroll, fine-loamy, mixed) soils in north-central South Dakota were sampled after pastures were established and 8 years later so that the effect of the pastures on soils could be studied from analysis in the laboratory. Pastures were seeded to Russian wildrye (Elymus junceus Fisch.), crested wheatgrass (Agropyron desertorum (Fisch.) Schult.), or a mixture smooth bromegrass (Bromus inermis Leyss.), intermediate wheatgrass (Agropyron intermedium (Host) Beauv.), a pasture alfalfa (Medicago sativa L.). Soil N and bulk densities increased as available P decreased in the 8 years. The soil organic matter increased under all pastures, but it was small. The increases in organic matter, decreases in available P, and increases in saturated-clod bulk densities were different in the various pastures. Total N and organic matter increased about 0.001 and 0.02% per year, respectively, which is slower than the rate of decrease caused by cultivating the original grassland soils.
  • Authors:
    • Woody, W. M.
    • Papendick, R. I.
    • Cochran, V. L.
  • Source: Agronomy Journal
  • Volume: 65
  • Issue: 4
  • Year: 1973
  • Summary: Potassium azide (KN3) and 2-chloro-6-(trichloromethyl) pyridine (N-Serve) were evaluated as nitrification inhibitors for anhydrous NH3 field applied on irrigated and nonirrigated Ritzville silt loam and on nonirrigated Naff silt loam in eastern Washington. Formulations of KN3, N-Serve in liquid NH3, or NH3 alone were applied to fallow soil in midsummer at a rate of 90 kg N/ha. Irrigations were 15 cm of water sprinkler applied 1 day or 2 weeks after fertilizer application, and 10 to 15 cm of water each time at 4, 8, and 13 weeks after NH3 application. The NH3 retention zone was sampled for NH+4 and NO-3 periodically through December for the Naff soil and through February for the Ritzville soil. Both KN3 and N-Serve effectively inhibited nitrification of the applied NH3 on nonirrigated Ritzville soil when temperature and soil moisture were favorable for rapid nitrification. However, KN3 was completely ineffective following irrigation or, for the Naff soil, after rainwater penetrated below the retention zone 2 weeks after N application. Where irrigated 1 day or 2 weeks after fertilization application, all of the applied N had disappeared from the initial NH3 retention zone in the Ritzville soil in 8 to 13 weeks for both NH3 alone and NH3 + KN3. Results with the Naff soil for these applications were similar to results with the irrigated Ritzville soil. By contrast, N-Serve effectively suppressed nitrification under leaching and nonleaching conditions. For the Ritzville soil, total N uptake by the wheat (Triticum aestivum L.) crop for different rates of fertilizer application followed the order of NH3 + KN3 > NH3 + N-Serve > NH3 alone, but grain yields with NH3 + inhibitor were not different from yields with NH3 alone. For the Naff soil there was no N-uptake or grain-yield response to N rates, and thus no response to the inhibitors.
  • Authors:
    • Larson, W. E.
    • Moldenhauer, W. C.
    • Morachan, Y. B.
  • Source: Agronomy Journal
  • Volume: 64
  • Issue: 2
  • Year: 1972
  • Summary: When well-fertilized corn (Zea mays L.) monocultures with large amounts of residues returned to the soil became common, the question was asked as to whether soil tilth and corn yields could be maintained at satisfactory levels in Corn Belt soils. To answer this question corn growth and soil physical properties were determined in a field experiment in which different types (alfalfa (Medicago sativa L.), cornstalks, sawdust, oatstraw (Avena sativa L.) and bromegrass (Bromus inermis Leyss)) and amounts (from O to 16 tons/ha/yr) of plant residues were added to Marshall silty clay loam (Typic Hapludoll) for 13 consecutive years. The soil was cropped to corn and large amounts of N were added. For approximately the first 9 years grain yields were lower from the check and sawdust treatments than from all others. During the last 4 years grain yields declined sharply with rate of addition of cornstalk residues and slightly from additions of alfalfa. It is suggested that the yield decline in the cornstalk treatments was due to a lowering of pH and an Al-induced Ca deficiency in the plant. An alternative explanation is that the cation balance was upset as evidenced by K/Ca and K/Ca + Mg ratios in the plant. The C content of the soil was progressively increased, as was the wet aggregate stability and water retention with rate of addition of organic material. Energy of aggregate rupture, energy to initial runoff, erosion, and infiltration were not significantly influenced. It was not visually evident that significant changes occurred in soil tilth because of treatment differences. Marshall soils are well aggregated, have favorable physical and chemical properties, and although erosive, physical problems are not usually observable in the field. Corn grain yields averaged near 7,000 kg/ha (112 bu/acre) in the later years of the experiment, again suggesting that the physical properties of the soil on all treatments were favorable.
  • Authors:
    • Zhu, X.
    • Zhuang, Q.
    • Qin, Z.
  • Source: GLOBAL CHANGE BIOLOGY BIOENERGY
  • Volume: 7
  • Issue: 1
  • Summary: This study estimated the potential emissions of greenhouse gases (GHG) from bioenergy ecosystems with a biogeochemical model AgTEM, assuming maize (Zea mays L.), switchgrass (Panicum virgatum L.), and Miscanthus (Miscanthus × giganteus) will be grown on the current maize-producing areas in the conterminous United States. We found that the maize ecosystem acts as a mild net carbon source while cellulosic ecosystems (i.e., switchgrass and Miscanthus) act as mild sinks. Nitrogen fertilizer use is an important factor affecting biomass production and N2O emissions, especially in the maize ecosystem. To maintain high biomass productivity, the maize ecosystem emits much more GHG, including CO2 and N2O, than switchgrass and Miscanthus ecosystems, when high-rate nitrogen fertilizers are applied. For maize, the global warming potential (GWP) amounts to 1-2 Mg CO2eq ha-1 yr-1, with a dominant contribution of over 90% from N2O emissions. Cellulosic crops contribute to the GWP of less than 0.3 Mg CO2eq ha-1 yr-1. Among all three bioenergy crops, Miscanthus is the most biofuel productive and the least GHG intensive at a given cropland. Regional model simulations suggested that substituting Miscanthus for maize to produce biofuel could potentially save land and reduce GHG emissions.
  • Authors:
    • Bement, R. E.
  • Source: Journal of Range Management
  • Volume: 22
  • Issue: 2
  • Year: 1969
  • Summary: A stocking-rate guide for cattle on blue-grama range was developed at Central Plains Experimental Range. The guide is based on the amount of herbage left ungrazed at the end of the summer season as it relates to gain per animal and gain per acre. Maximum dollar returns per acre from yearlings were obtained when 300 lb of air-dry herbage were left at the end of the season. The average optimum stocking rate was 2.6 acres/yearling month.
  • Authors:
    • Horner, G. M.
  • Source: Agronomy Journal
  • Volume: 52
  • Issue: 6
  • Year: 1960
  • Summary: Crop rotations that include legume-grass sod crops are more effective for runoff and erosion control, soil organic matter maintenance, and high wheat yields than the unfertilized pea-wheat and fallow-wheat systems. Summer fallowing causes the largest erosion losses and the most rapid depletion of organic matter.
  • Authors:
    • Fetter, J. C.
    • Brown, R. N.
    • Gorres, J. H.
    • Lee, C.
    • Amador, J. A.
  • Source: Water, Air, & Soil Po9llution
  • Volume: 223
  • Issue: 4
  • Year: 0201
  • Summary: Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic burden on processors. A potential solution to this problem involves converting squid by-products into an organic fertilizer, for which there is growing demand. Because fertilizer application to lawns can increase the risk of nutrient contamination of groundwater, we quantified leaching of NO 3-N and PO 4-P from perennial ryegrass turf ( Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) and synthetic (SY). Field plots were established on an Enfield silt loam, and liquid (L) and granular (G) fertilizer formulations of squid and synthetic fertilizers were applied at 0, 48, 146, and 292 kg Nha -1 year -1. Levels of NO 3-N and PO 4-P in soil pore water from a depth of 60 cm were determined periodically during the growing season in 2008 and 2009. Pore water NO 3-N levels were not significantly different among fertilizer type or formulation within an application rate throughout the course of the study. The concentration of NO 3-N remained below the maximum contaminant level (MCL) of 10 mg L -1 until midSeptember 2009, when values above the MCL were observed for SQG at all application rates, and for SYL at the high application rate. Annual mass losses of NO 3-N were below the estimated inputs (10 kg Nha -1 year -1) from atmospheric deposition except for the SQG and SYL treatments applied at 292 kg Nha -1 year -1, which had losses of 13.2 and 14.9 kg Nha -1 year -1, respectively. Pore water PO 4-P levels ranged from 0 to 1.5 mg PL -1 and were not significantly different among fertilizer type or formulation within an application rate. Our results indicate that N and P losses from turf amended with squid-based fertilizer do not differ from those amended with synthetic fertilizers or unfertilized turf. Although organic in nature, squid-based fertilizer does not appear to be more-or less-environmentally benign than synthetic fertilizers.