• Authors:
    • Campbell, C. A.
    • Derksen, D. A.
    • Lafond, G. P.
    • Zentner, R. P.
  • Source: Soil & Tillage Research
  • Volume: 67
  • Issue: 1
  • Year: 2002
  • Authors:
    • Nelson, R. G.
  • Source: Biomass and Bioenergy
  • Volume: 22
  • Issue: 5
  • Year: 2002
  • Summary: The focus of this study was to develop a methodology to estimate "hectare-weighted", county-level, corn stover and spring and winter wheat straw removable residue quantities in the USA for 1995-1997 in 37 states (north-south line from North Dakota to Texas and all states east) such that tolerable rainfall and wind soil loss limits were not exceeded.
  • Authors:
    • Westfall, D. G.
    • Peterson, G. A.
    • Ortega, R. A.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 4
  • Year: 2002
  • Summary: Crop residue is a valuable resource in Great Plains dryland agroecosystems because it aids in water conservation and soil erosion control. The objectives of our research were to (i) determine the effect of cropping intensity, climate gradient, and soil depth on levels and changes in soil C, soil N, and residue parameters after 8 yr of no-till management in dryland cropping systems and (ii) relate soil and residue parameters to soil C and N levels. Surface soil properties and residue parameters were compared in two cropping systems, wheat (Triticum aestivum L.)-fallow (WF) and wheat-corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench]-proso millet (Panicum miliaceum L.)-fallow (WCMF). The effects were examined on the summit position of a catenary sequence of soils across three environments representing an evapotranspiration (ET) gradient. Soils at the low- and medium-ET sites are classified as Argiustols, and the soil at the high-ET site is an Ustochrept. There was 3.0 Mg ha-1 of residue in the surface 10 cm of soil compared with 2.7 Mg ha-1 of residue on the soil surface averaged over ET gradient and cropping systems. About 90% of the residue in the soil was found within the 2.5-cm soil depth. The highest soil organic C (SOC) and soil organic N (SON) were observed in the surface 0- to 2.5-cm depth. There was a trend (P [<=] 0.16) for the more intense WCMF cropping system to have higher SOC and SON contents than the traditional WF system (C = 6.6 g kg-1 for WF compared with 7.5 g kg-1 for WCMF and N = 0.70 g kg-1 for WF compared with 0.74 g kg-1 for WCMF). From 1985 to 1993, gains in SOC (967 kg ha-1) and SON (74 kg ha-1) occurred in the surface 0- to 2.5- and 2.5- to 5-cm depths while losses were observed in the 5- to 10-cm depth (SOC = -694 kg ha-1; SON = -44 kg ha-1). Climate strongly modified these effects but did not reflect a clear ET gradient effect. The results suggest that higher levels of surface SOC and SON can be attained by increasing cropping intensity under no-till management.
  • Authors:
    • Lukina, E. V.
    • Thomason, W. E.
    • Freeman, K. W.
    • Mullen, R. W.
    • Stone, M. L.
    • Johnson, G. V.
    • Solie, J. B.
    • Raun, W. R.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 4
  • Year: 2002
  • Summary: In 2001, N fertilizer prices nearly doubled as a result of increased natural gas prices. This was further troubling when considering that the world N use efficiency (NUE) in cereal grain production averages only 33%. Methods to improve NUE in winter wheat (Triticum aestivum L.) have not included high spatial-resolution management based on sensed plant growth properties nor on midseason prediction of grain yield. Our objective was to determine the validity of using in-season estimates of grain yield (INSEY) and a response index (RI) to modulate N at 1-m(2) spatial resolution. Four winter wheat field experiments were conducted that evaluated prescribed midseason N applications compared with uniform rates that simulated farmer practices. Our methods recognize that each 1-m(2) area in wheat fields needs to be sensed and managed independently and that the need for fertilizer N is temporally dependent. Averaged over locations, NUE was improved by >15% when N fertilization was based on optically sensed INSEY, determined for each 1-m(2) area, and a RI compared with traditional practices at uniform N rates.
  • Authors:
    • Albrecht, A.
    • Sa, J. C. D.
    • Ogle, S. M.
    • Denef, K.
    • Feller, C.
    • Six, J.
  • Source: Agronomie
  • Volume: 22
  • Issue: 7
  • Year: 2002
  • Summary: The long-term stabilization of soil organic matter (SOM) in tropical and temperate regions is mediated by soil biota (e. g. fungi, bacteria, roots and earthworms), soil structure (e. g. aggregation) and their interactions. On average, soil C turnover was twice as fast in tropical compared with temperate regions, but no major differences were observed in SOM quality between the two regions. Probably due to the soil mineralogy dominated by 1:1 clay minerals and oxides in tropical regions, we found a higher aggregate stability, but a lower correlation between C contents and aggregate stability in tropical soils. In addition, a smaller amount of C associated with clay and silt particles was observed in tropical versus temperate soils. In both tropical and temperate soils, a general increase in C levels (approximate to 325 +/- 113 kg C.ha(-1).yr(-1)) was observed under no-tillage compared with conventional tillage. On average, in temperate soils under no-tillage, compared with conventional tillage, CH4 uptake (approximate to0.42 +/- 0.10 kg C-CH4.ha(-1) yr(-1)) increased and N2O emissions increased (approximate to 1.95 +/- 0.45 kg N-N2O.ha(-1).yr(-1)). These increased N2O emissions lead to a negative global warming potential when expressed on a CO2 equivalent basis.
  • Authors:
    • Kimble, J. M.
    • Lal, R.
    • Jacinthe, P. A.
  • Source: Soil & Tillage Research
  • Volume: 67
  • Year: 2002
  • Summary: Enhancement of soil organic carbon (SOC) stocks through mulching has been proposed, and although this practice can alter several soil properties, its impact on the temporal variability of carbon dioxide (CO2) emission from soils has not been widely investigated. To that end, we monitored CO2 fluxes from a central Ohio Luvisol (fine, mixed, mesic Aeric Ochraqualf) amended with wheat (Triticum aestivum L.) straw applied at rates of 0 (M0), 8 (M8) and 16 (M16)Mgdry matter ha1 per year and supplemented with fertilizer (244 kg per year) or without. The experimental design was a randomized complete block design with three replications. The intensity of CO2 emission was higher in the late winter (mean: 2.79 g 2 per day) and summer seasons (2.45 gCO2- 2 per day) and lowest in the autumn (1.34 gCO2- 2 per day). While no significant effect of N fertilization on CO2 emission was detected, soil mulching had a significant effect on the seasonal variation of CO2 fluxes. The percentage of annual CO2 emitted during the winter and spring was similar across treatments (17-22%); however, 43% of the annual CO2 loss in the M0 plots occurred during the summer as opposed to 26% in the mulch treatments. A close relationship (F = 0.47X +4.45, R2 = 0.97,P <0.001) was found between annual CO2 flux (F, MgCO2-C ha 1) and residue-C input (X,MgCh 1). Litter and undecomposed residue amounted to 0.32 and 0.67MgC ha 1 per year in the M8 and M16 plots, respectively. After 4 years of straw application, SOC stocks (0-10 cm) were 19.6, 25.6 and 26.5MgCh1 in the M0, M8 and M16 treatments, respectively. The results show that soil mulching has beneficial effect on SOC sequestration and strongly influence the temporal pattern of CO2 emission from soils.
  • Authors:
    • Mosier, A. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 63
  • Issue: 2
  • Year: 2002
  • Summary: Human-induced input of fixed nitrogen (N) into the earth biosphere, primarily through combustion of fossil fuels, crop biological N-fixation and N-fertilizer use, has provided many human benefits. These benefits have not come, however, without significant cost. According to data compiled by the Food and Agriculture Organization of the United Nations, synthetic N fertilizer input into global agricultural systems increased from by approximately 430% (~19 to ~82 Tg N) from 1965 to 1998. During this period, global grain production, human population and global fossil fuel consumption increased about 250%, 190% and 240%, respectively. Although fuel consumption increased faster than population growth globally, land used to produce grain decreased from 0.2 to 0.12 ha/person over this 30-yr period. Grain production, however, increased 16%/person. Agricultural production increase has come through the use of new crop varieties which respond to increased N-fertilization, pesticide use, irrigation and mechanization. Even though agricultural production has increased dramatically, fertilizer N use efficiency remains relatively low. Globally fertilizer N use efficiency was approximately 50% in 1996. Since fertilizer N is not used efficiently in most parts of the world, N use in excess of crop potential utilization leads to losses to the environment through volatilization and leaching. These N losses result in N fertilization of pristine terrestrial and aquatic systems through NHx and NOydeposition and contribute to global greenhouse gases through N2O production and local elevated ozone concentrations due to NOx emission. Inefficient use of N and energy is exacerbated by the global inequity of use distribution. Some areas don't have enough while others use too much. Additionally, dietary patterns of food consumption which tend to be more inefficient, i.e. cereal-based diets compared to animal-based diets, are changing in global terms. The resulting increasing inefficiencies in N utilization in food production and in energy use lead to large-scale input of N into down wind and down stream terrestrial and aquatic systems. Increasing N-use-efficiency remains a clear goal by which to maintain food production while decreasing excessive N use and unwanted distribution in the environment.
  • Authors:
    • Schimel, D. S.
    • Peterson, G. A.
    • Mosier, A.
    • Parton, W.
    • Ojima, D.
    • Del Grosso, S.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: Supplement 1
  • Year: 2002
  • Summary: We present evidence to show that DAYCENT can reliably simulate soil C levels, crop yields, and annual trace gas fluxes for various soils. DAYCENT was applied to compare the net greenhouse gas fluxes for soils under different land uses. To calculate net greenhouse gas flux we accounted for changes in soil organic C, the C equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Model results and data show that dryland soils that are depleted of C due to conventional till winter wheat/fallow cropping can store C upon conversion to no till, by reducing the fallow period, or by reversion to native vegetation. However, model results suggest that dryland agricultural soils will still be net sources of greenhouse gases although the magnitude of the source can be significantly reduced and yields can be increased upon conversion to no till annual cropping. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • Authors:
    • Reule, C. A.
    • Peterson, G. A.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 6
  • Year: 2002
  • Summary: Winter wheat (Triticum aestivum L.)-fallow (WF) using conventional stubble mulch tillage (CT) is the predominant production practice in the central Great Plains and has resulted in high erosion potential and decreased soil organic C (SOC) contents. This study, conducted from 1990 through 1994 on a Weld silt loam (Aridic Argiustoll) near Akron, CO, evaluated the effect of WF tillage system with varying degrees of soil disturbance [no-till (NT), reduced till (RT), CT, and bare fallow (BF)] and crop rotation [WF, NT wheat-corn (Zea mays L.)-fallow (WCF), and NT continuous corn (CC)] on winter wheat and corn yields, aboveground residue additions to the soil at harvest, surface residue amounts at planting, and SOC. Neither tillage nor crop rotation affected winter wheat yields, which averaged 2930 kg ha-1. Corn grain yields for the CC (NT) and WCF (NT) rotations averaged 1980 and 3520 kg ha-1, respectively. The WCF (NT) rotation returned 8870 kg ha-1 residue to the soil in each 3-yr cycle, which is 2960 kg ha-1 on an annualized basis. Annualized residue return in WF averaged 2520 kg ha-1, which was 15% less than WCF (NT). Annualized corn residue returned to the soil was 3190 kg ha-1 for the CC (NT) rotation. At wheat planting, surface crop residues varied with year, tillage, and rotation, averaging WCF (NT) (5120 kg ha-1) > WF (NT) (3380 kg ha-1) > WF (RT) (2140 kg ha-1) > WF (CT) (1420 kg ha-1) > WF (BF) (50 kg ha-1). Soil erosion potential was lessened with WCF (NT), CC (NT), and WF (NT) systems because of the large amounts of residue cover. Levels of SOC in descending order in 1994 were CC (NT) [>=] WCF (NT) [>=] WF (NT) = WF (RT) = WF (CT) > WF (BF). Although not statistically significant, the CC (NT) treatment appeared to be accumulating more SOC than any of the rotations that included a fallow period, even more rapidly than WCF (NT), which had a similar amount of annualized C addition. Reduced tillage and intensified cropping increased SOC and reduced soil erosion potential.
  • Authors:
    • Black, A. L.
    • Wienhold, B. J.
    • Halvorson, A. D.
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 3
  • Year: 2002
  • Summary: Soil C sequestration can improve soil quality and reduce agriculture's contribution to CO2 emissions. The long-term (12 yr) effects of tillage system and N fertilization on crop residue production and soil organic C (SOC) sequestration in two dryland cropping systems in North Dakota on a loam soil were evaluated. An annual cropping (AC) rotation [spring wheat (SW) (Triticum aestivum L.)-winter wheat (WW)-sunflower (SF) (Helianthus annuus L.)] and a spring wheat-fallow (SW-F) rotation were studied. Tillage systems included conventional-till (CT), minimum-till (MT), and no-till (NT). Nitrogen rates were 34, 67, and 101 kg N ha-1 for the AC system and 0, 22, and 45 kg N ha-1 for the SW-F system. Total crop residue returned to the soil was greater with AC than with SW-F. As tillage intensity decreased, SOC sequestration increased (NT > MT > CT) in the AC system but not in the SW-F system. Fertilizer N increased crop residue quantity returned to the soil, but generally did not increase SOC sequestration in either cropping system. Soil bulk density decreased with increasing tillage intensity in both systems. The results suggest that continued use of a crop-fallow farming system, even with NT, may result in loss of SOC. With NT, an estimated 233 kg C ha-1 was sequestered each year in AC system, compared with 25 kg C ha-1 with MT and a loss of 141 kg C ha-1 with CT. Conversion from crop-fallow to more intensive cropping systems utilizing NT will be needed to have a positive impact on reducing CO2 loss from croplands in the northern Great Plains.