• Authors:
    • Kissel, D. E.
    • Havlin, J. L.
  • Source: Soil Organic Matter in Temperate Agroecosystems: Long-Term Experiments in North America
  • Volume: 1
  • Year: 1997
  • Authors:
    • Mallarino, A. P.
    • Voss, R. D.
    • Blackmer, A. M.
  • Source: Iowa State Cooperative Extension publication
  • Year: 1997
  • Summary: Nitrogen fertilizer recommendations for corn in the state of Iowa, USA.
  • Authors:
    • Voroney, R.
    • Vyn, T.
    • Janovicek, K.
  • Source: Agronomy Journal
  • Volume: 89
  • Issue: 4
  • Year: 1997
  • Summary: Research in Ontario, Canada in 1989, 1990, and 1995 evaluated no-till maize yield response to various preceding crops and examined whether in-row residue removal affected no-till maize response to rotation crops. The soil was an imperfectly drained loam (medium, mixed, weakly to moderately calcareous Typic Hapludalf). The preceding crops were: maize harvested for grain or whole-plant silage; hard red spring wheat; barley; red clover ( Trifolium pratense) cover crops, following barley, that were killed by spraying either 3 weeks (early-kill) or 1 day (late-kill) prior to sowing maize; canola [rape]; and soyabeans. In-row residue was either retained while sowing or cleared using planter-mounted, notched-disc row cleaners. Clearing in-row cover crop residue increased early-season maize growth and was associated with yield increases of 0.61 t ha -1 (8%) following early-killed red clover and 0.43 t ha -1 (6%) ( P = 0.10) following late-killed red clover. In 2 of 3 years, maize yields following early-killed red clover were similar to following soyabeans and greater than following grain maize, provided that in-row residue was cleared. Following the other crops, grain yield response to clearing in-row residue was smaller and less consistent over years. Preceding cropping affected early-season maize growth, with the largest plants at 5 weeks after sowing following either soyabeans or silage maize and the smallest following either red clover or grain maize. In 2 of 3 years, when preceding crop effects on grain yield were statistically significant, yields following either soyabeans or spring wheat were more than 1.05 t ha -1 (16%) higher than after grain maize. That yield increase occurred regardless of in-row residue placement. Removing maize stover by harvesting as silage increased maize yield by 0.86 t ha -1 (12%) over yield following grain maize. During 1995, maize yield following silage maize was less than after soyabeans, canola, barley, or wheat; thus, no-till maize yield response to rotation is not exclusively due to the presence of surface-placed stover. In-row residue placement and preceding cropping practices affected in-row soil temperature, but this could not totally account for the treatment effects on early-season maize growth and yields.
  • Authors:
    • Maddux, L. D.
    • Gordon, W. B.
    • Rice, C. W.
    • Omay, A. B.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL Pages:
  • Volume: 61
  • Issue: 6
  • Year: 1997
  • Summary: With renewed interest in maintaining our soil resources, it is important to establish criteria that can describe and quantify the effect of different crop management practices on soil organic matter (SOM). We conducted this study to assess changes in SOM and other soil properties after long-term (>10 yr) continuous corn (Zea mays L.; CC) and corn-soybean rotation [Glycine max (L.) Merr,; C/SB] with and without fertilizer, Soil samples were collected from two furrow-irrigated CC and C/SB rotations on a Crete silt loam (ene, montmorillonitic, mesic Pachic Argiustoll) and a Eudora loam (coarse-silty, mixed, mesic Fluventic Hapludoll). Long term (350-d) laboratory incubation at optimum moisture and temperature conditions measured potentially mineralizable C (PMC) and N (PMN) as a measure of the active fraction of soil organic C and N, Microbial biomass C (MBC) and N (MBN), organic C and N, pH, and texture also were determined, Crop rotations that included high-residue-producing crops such as corn and addition of fertilizer increased soil organic C and N, Crop rotation did not affect PMC in the Crete soil, but addition of fertilizer significantly increased PMC by 32%. The PMN in both soils was not affected by crop rotation or fertilizer addition, Inclusion of soybean in the rotation decreased the stable and active fractions of organic C and N, Changes in soil organic C and N in response to crop rotation and fertilizer addition were related to the estimated amount of crop residues returned to the soil and to soil texture.
  • Authors:
    • Bauer, P. J.
    • Hunt, P. G.
    • Matheny, T. A.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 3
  • Year: 1997
  • Summary: Cotton (Gossypium hirsutum L.) production has dramatically increased in the Southeast, but the role of conservation tillage in doublecropped cotton systems has not been clearly defined. Therefore, from 1988 to 1994, we investigated doublecropped wheat (Triticum aestivum L.) and cotton on plots that had been in continuous conservation vs. conventional tillage since 1979. The experimental site wits located near Florence, SC, on a Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Kandiudult). Conventional tillage consisted of multiple diskings and cultivations; surface tillage was eliminated for conservation tillage. Wheat yields were not significantly affected by tillage, but cotton yields were significantly higher for conservation tillage (P less than or equal to 0.01). Cotton planting dates ranged from 7 to 18 June, and 5 of the 7 yr had more than 145 frost-free days. Two years had crop failure because of early freezes, and a June drought prevented the planting of cotton in 1 yr. In the 4 yr with harvestable yields, seed cotton yields among the eight cultivars ranged from about 500 to 2200 and 300 to 1850 lb/acre for conservation and conventional tillage, respectively. The early maturing cultivar, 'Deltapine (DP) 20,' had the highest seed cotton yields with means of 1442 and 1123 lb/acre for conservation and conventional tillage, respectively Development of earlier maturing cotton and wheat cultivars will be important for this cropping system in the northern Coastal Plain portion of the Cotton Belt.
  • Authors:
    • Walters, D. T.
    • Kessavalou, A.
  • Source: Agronomy Journal
  • Volume: 89
  • Issue: 1
  • Year: 1997
  • Summary: Rotation of corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] provides certain economic and environmental advantages over monoculture corn. Low soybean residue production and persistence, however, promote potentially excessive soil erosion following soybean harvest. An irrigated field experiment was conducted in eastern Nebraska for 4 yr (1990-1993) under various tillage treatments and N rates to evaluate the effects of a winter rye (Secale cereale L.) cover crop following soybean on (i) rye dry matter yield, (ii) surface residue cover for erosion protection, and (iii) corn establishment and production. The soil was a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls). Treatments were (i) no-tillage and disk tillage; (ii) corn following soybean with a winter rye cover crop (CBR), corn following soybean without rye (CB) and corn following corn (CC); and (iii) 0, 50, 100, 150, and 300 kg N ha(-1) (applied to corn). Rye aboveground dry matter yield, surface residue cover, and corn yield parameters were estimated. Rye dry matter yield ranged from 0.25 to 2.9 Mg ha(-1) and was influenced by tillage, N rate, and weather conditions in different years. During the years of high rye dry matter yield, presence of rye in the corn-soybean system gave approximately 16% additional surface residue cover prior to planting through cultivation, compared with soybean residue alone. Surface cover by rye and soybean residues in CBR was equivalent to corn residue in CC under both disk and no-till management. In 1 of the 3 yr, corn plant population and grain yield were reduced following rye (CBR) compared with the no rye system (CB), possibly due to apparent allelopathic effects related to the age of rye. No significant difference in N response was observed between CBR and CB corn yields. In general, rotation of corn with soybean (with and without rye) resulted in an increase of approximately 27% in corn grain yield and N uptake over continuous corn. During the years of high rye dry matter production, rye accumulated approximately 45 kg N ha(-1) through aboveground dry matter. Overall, including a winter rye cover crop in the corn-soybean rotation system was beneficial.
  • Authors:
    • Kitchen, N. R.
    • Westfall, D. G.
    • Peterson, G. A.
    • Kolberg, R. L.
  • Source: Journal of Production Agriculture
  • Volume: 9
  • Issue: 4
  • Year: 1996
  • Summary: Crop N needs are not usually predicted based on cropping intensity or on tillage practice. However, N fertilizer requirements may increase dramatically as less fallow and less tillage are used in semi-arid regions of the Great Plains where summer fallow cropping is common. This long-term experiment was conducted to study the influence of N fertilizer rate, source/placement/timing (NSP), and crop rotation factors on the production of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor L.), as well as their fertilizer N use efficiency (FNUE) for the initial years of conversion to no-till dryland farming. Research was conducted from 1987 through 1992 on two soils (Keith clay loam, a fine-silty, mixed, mesic Aridic Argiustoll and Weld loam, a fine-silty, mixed, mesic, Aridic Argiustoll) in eastern Colorado. Rotations included winter wheat-fallow (WF) and winter wheat-corn or grain sorghum-fallow (WCF). Wheat yields were similar between WF and WCF with adequate N application. Response to N fertilizer at lower rates was greater in WCF than WF because of its greater depletion of soil N. Corn production averaged 72 bu/acre with adequate N and required 1 lb/acre of N uptake to produce 1 bu/acre of grain. Current N fertilizer recommendations for wheat and corn were not adequate to insure maximum production under no-till management. Fertilizer placement significantly affected average annual rotational yield (40 to 70 lb/acre per yr difference) but application rate was more important economically. Grain biomass produced in each rotation per pound of total plant N uptake (GNUE) was 17 lb/acre per yr in WF compared with 29 lb/acre per yr for WCF. This 70% increase in average annual grain production of WCF over WF was accomplished with a 44% annual increase in fertilizer N application.
  • Authors:
    • Dhuyvetter, K. C.
    • Thompson, C. R.
    • Norwood, C. A.
    • Halvorson, A. D.
  • Source: Journal of Production Agriculture
  • Volume: 9
  • Issue: 2
  • Year: 1996
  • Summary: Dryland wheat (Triticum aestivum L.) in the Great Plains generally is planted in a wheat- fallow (WF) rotation. Wheat grown in rotation with a summer row crop like corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], or sunflower [Helianlhus annuus var. macrocarpus (DC,) Ck11.] increases cropping intensity, allowing a crop to be produced annually on 67 to 100% of tillable acres. A review of economic analyses of dryland cropping systems in the Great Plains was conducted to compare net returns, production costs, financial risk, and compatibility with the 1990 Farm Bill. Seven of eight studies reported that net returns were greater from a more intensive crop rotation than from WF when reduced-tillage (RT) or no-till (NT) were used following wheat harvest and prior to the summer crop planting, With government program payments, WF was more profitable with conventional tillage (CT) than with NT. Production costs increased as cropping intensity increased and tillage decreased. Economic risk analysis showed that wheat-sorghum-fallow (WSF) was less risky than WF in Kansas. Cropping systems using more intensive rotations with less tillage had higher production costs than WF, but also had increased net returns and reduced financial risk, while remaining in compliance with 1990 Farm Bill provisions.
  • Authors:
    • Harriss, R. C.
    • Narayanan, V.
    • Li, C.
  • Source: Global Biogeochemical Cycles
  • Volume: 10
  • Issue: 2
  • Year: 1996
  • Summary: The Denitrification-Decomposition (DNDC) model was used to elucidate the role of climate, soil properties, and farming practices in determining spatial and temporal variations in the production and emission of nitrous oxide (N[2]O) from agriculture in the United States. Sensitivity studies documented possible causes of annual variability in N[2]O flux for a simulated Iowa corn-growing soil. The 37 scenarios tested indicated that soil tillage and nitrate pollution in rainfall may be especially significant anthropogenic factors which have increased N[2]O emissions from soils in the United States. Feedbacks to climate change and biogeochemical manipulation of agricultural soil reflect complex interactions between the nitrogen and carbon cycles. A 20% increase in annual average temperature in °C produced a 33% increase in N[2]O emissions. Manure applications to Iowa corn crops enhanced carbon storage in soils, but also increased N[2]O emissions. A DNDC simulation of annual N[2]O emissions from all crop and pasture lands in the United States indicated that the value lies in the range 0.9 - 1.2 TgN. Soil tillage and fertilizer use were the most important farming practices contributing to enhanced N[2]O emissions at the national scale. Soil organic matter and climate variables were the primary determinants of spatial variability in N[2]O emissions. Our results suggest that the United States Government, and possibly the Intergovernmental Panel on Climatic Change (IPCC), have underestimated the importance of agriculture as a national and global source of atmospheric N[2]O. The coupled nature of the nitrogen and carbon cycles in soils results in complex feedbacks which complicate the formulation of strategies to reduce the global warming potential of greenhouse gas emissions from agriculture.
  • Authors:
    • Yoo, K. H.
    • Shirmohammadi, A.
    • Yoon, K. S.
    • Rawls, W. J.
  • Source: Journal of Environmental Science and Health . Part A: Environmental Science and Engineering and Toxicology
  • Volume: 31
  • Issue: 3
  • Year: 1996
  • Summary: A Continuous version of distributed parameter model, ANSWERS (ANSWERS 2000) was applied to a field-sized watershed planted to cotton in the Limestone Valley region of northern Alabama. The field was cultivated for three years with conventional tillage followed by three years of conservation tillage. Overall, the ANSWERS model simulated runoff and nutrient losses in surface runoff within an acceptable range for the conventional tillage system conditions in continuous simulation mode. But the sediment losses predicted by ANSWERS were initially on the order of fifteen times or more higher than measured regardless of tillage systems. In order to duplicate measured data, the sediment detachment coefficient of rainfall and flow had to be reduced for calibration. The model poorly predicted soluble nutrient losses for the conservation tillage system due to the model's weakness in representing the surface application of fertilizer under this practice. The model simulates only one soil layer, in which soil moisture, nutrient concentration, and soil characteristics are assumed homogeneous. Currently, the model does not consider vertical nutrient concentration variation in soil profile. During the conservation tillage system, corn stalk and the residue of a winter cover crop were spread on the soil surface. However, the model did not properly represent surface spreading of crop residue, thus the model was unable to consider the organic-nitrogen contribution from crop residue to the erodible soil surface. This resulted in poor prediction of sediment-bound TKN, especially for conservation tillage system.