• Authors:
    • Madramootoo, C. A.
    • Mehuys, G. R.
    • Burgess, M. S.
  • Source: Agronomy Journal
  • Volume: 88
  • Issue: 5
  • Year: 1996
  • Summary: Reduced tillage is often recommended to decrease soil degradation and erosion associated with intensive row cropping. This study assessed the effects of different tillage and crop residue levels on corn (Zea mays L.) yields and related factors on a 2.4-ha site in southwestern Quebec over a 3-yr period. The soil, a Typic Endoaquent, consisted of sandy loam or loamy sand (mean depth, 46 cm) overlying clay, with subsurface drains at the 1.2-m depth. Treatments, begun in fall 1991, consisted of no-till (NT), reduced tillage (RT; dished in fall and spring), and conventional tillage (CT; moldboard-plowed in fall, dished in spring), in combination with two crop residue levels: no residue (-R; grain and stover removed at harvest, as for silage corn) and with residue (+R; stover left on site at harvest, as for grain corn). High crop-residue mulches resulted from NT+R (77-97% of soil surface covered), RT+R (45-92%), and at times NT-R (8-35%), potentially protecting the soil from erosive forces. Seedling emergence was delayed (1992, 1993) or partly suppressed (1994) in NT+R, and was also delayed in CT+R in 1992 and 1993, and in CT-R and RT+R in 1993. Final populations were affected only in 1993. In -R (silage) plots, yields with NT and RT were either greater (1992) or the same as their CT counterparts. On +R (grain) plots, grain, stover, and total yields were lower with NT in 1992 and 1994, due in part to difficulties in planting through the residue mulch, while RT reduced grain, stover, and total yields in 1992 and stover and total yields in 1993. Thus, for silage-corn production, NT and RT may offer economically viable alternatives to CT, although the use of dishing for a RT system provides almost no protective residue cover. In continuous grain corn, high residue buildup with NT and RT requires special attention to seeding technique or yield losses may result.
  • Authors:
    • De Jong, B. H. G.
    • Montoya-Gómez, G.
    • Nelson, K.
    • Soto-Pinto, L.
    • Taylor, J.
    • Tipper, R.
  • Source: Interciencia
  • Volume: 20
  • Issue: 6
  • Year: 1995
  • Summary: Although forestry and agroforestry are recognized as promising land-use alternatives for reducing the increasing levels of global atmospheric carbon, the viability of carbon sequestration projects at the land-user level has rarely been evaluated. We present the results of a feasibility study to: (1) evaluate the interest of local communities in a carbon sequestration project and how they would organize themselves for the proposed forestry project; (2) identify the carbon sequestration potential of the agroforestry/forestry systems that are both ecologically viable and preferred by local farmers (3) determine the social constraints of and potential for, such projects,- and (4) assess the economic potential of the carbon offsets estimated for such systems. This project was carried out by an interdisciplinary team of scientists and farmers in two ecological regions: the Tojolabal and Tzeltal zones of Chiapas, Mexico. Five systems with high carbon sequestration potential were considered technically and socially viable for each region. Initially, all participants will plant trees on an individual basis in their coffee plantation, fallow, and pasture lands, or in their maize fields. The estimated amount of carbon sequestered ranged from 46 7 to 236 7 tons of carbon per hectare (tC/ha). Net income benefits due to converting fields from maize cultivation to farm forestry ranged from $500-1000/ha depending on the value assigned to the sequestered carbon.1 Forests and farm woodlands that are sustainably managed have substantial economic and carbon sequestration potential. The principal barrier to communal forest management appears to be sociopolitical rather than economic. Because forest management requires long-term investments, good planning is essential and includes community control of projects, selection of appropriate tree species, and management techniques that are specific to the ecological and social conditions of the area. 1 All references to dollars in this report refer to U.S. dollars ($US).
  • Authors:
    • Lamm,F. R.
    • Manges,H. L.
    • Stone,L. R.
    • Khan,A. H.
    • Rogers,D. H.
  • Source: Transactions of the ASAE
  • Volume: 38
  • Issue: 2
  • Year: 1995
  • Summary: Irrigation development during the last 50 years has led to overdraft in many areas of the large Ogallala aquifer in the central United States. Faced with the decline in irrigated acres, irrigators and wafer resource personnel are examining many new techniques to conserve this valuable resource. A three-year study (1989 to 1991) was conducted on a Keith silt loam soil (Aridic Argiustoll) in northwest Kansas to determine the water requirement of corn (Zea mays L.) grown using a subsurface drip irrigation (SDI) system. A dryland control and five irrigation treatments, designed to meet from 25 to 125% of calculated evapotranspiration (ET) needs of the crop were examined. Although cumulative evapotranspiration and precipitation were near normal for the three growing seasons, irrigation requirements were higher than normal due to the timing of precipitation and high evapotranspiration periods. Analysis of the seasonal progression of soil water revealed the well-watered treatments (75 to 125% of ET treatments) maintained stable soil water levels above approximately 55 to 60% of field capacity for the 2.4-m soil profile; while the deficit-irrigated treatments (no irrigation to 50% of ET treatments) mined the soil water. Corn yields were highly linearly related to calculated crop water use, producing 0.048 Mg/ha of grain for each millimeter of water used above a threshold of 328 mm. Analysis of the calculated water balance components indicated that careful management of SDI systems can reduce net irrigation needs by nearly 25%, while still maintaining top yields of 12.5 Mg/ha. Most of these water savings can be attributable to minimizing nonbeneficial water balance components such as soil evaporation and long-term drainage. The SDI system is one technology that can make significant improvements in water use efficiency by better managing the water balance components.
  • Authors:
    • Rowell, A. L.
    • Weinrich, K. B.
    • Barnwell, T. O.
    • Jackson, R. B.,IV
    • Patwardhan, A. S.
    • Donigian, A. S.
  • Source: Soil Management and Greenhouse Effect
  • Year: 1995
  • Authors:
    • McIntosh, M. S.
    • Mulford, F. R.
    • Meisinger, J. J.
    • Decker, A. M.
    • Clark, A. J.
  • Source: Agronomy Journal
  • Volume: 87
  • Issue: 3
  • Year: 1995
  • Summary: Hairy vetch (Vicia villosa Roth) can fix N-2 for subsequent release to a corn (Zea mays L.) crop, but kill date effects on vetch N accumulation, soil water, and subsequent corn production have not been studied. A hairy vetch cover crop can deplete soil water through transpiration, but cover crop mulches can conserve soil water for no-till corn. In order to determine optimum spring kill date and corn fertilizer N (FN) rates, hairy vetch was killed early April, late April, or mid-May, followed by three corn planting dates and four FN rates (0, 45, 135, and 202 kg N ha(-1)). From early April to mid-May, hairy vetch aerial phytomass and N content increased significantly, from 2800 to 4630 and 96 to 149 kg ha(-1), respectively. Corn grain yields ranged from 5.2 to 10.1 Mg ha(-1) and were significantly greater following mid or late kill, compared with early kill of vetch, regardless of corn planting date or FN rate. Gravimetric soil water under mid- or late-kill vetch was often significantly greater than after early-kill vetch. We conclude that soil water conservation by late-killed vetch mulches had a greater influence on corn production than vetch spring water use. Optimum N production and water conservation occurred when vetch was killed the last week of April. Early-kill vetch sacrificed N production and minimized soil water conservation, resulting in reduced corn grain yield. Late kill did not add significant N benefits, but could deplete soil water or interfere with timely corn planting.
  • Authors:
    • Cote, D.
    • Voroney, R. P.
    • Angers, D. A.
  • Source: Soil Science Society of America Journal
  • Volume: 59
  • Issue: 5
  • Year: 1995
  • Summary: This study was conducted to determine the influence of tillage practices on the decomposition of corn (Zea mays L.) residues and turnover of soil organic matter (SOM). Measurements of {delta}13C were made of the whole soil, the microbial biomass, and two particle-size fractions (50 {micro}m) in soils that had been under corn production for 11 yr and from an adjacent meadow. Meadow-derived C in total SOM (0-24 cm) decreased under corn cropping at the same rate under all tillage treatments. Corn-derived C was evenly distributed with depth in the moldboard plow treatment and accumulated at the surface in the shallow, reduced-tillage treatments. The incorporation of corn residue C into SOM in the 0- to 24-cm layer was not significantly affected by tillage and was estimated to be {approx}41 g C m-2 yr-1, which represents {approx}30% of the corn residue inputs. Both the macroorganic matter (>50 {micro}m) and microbial biomass had a greater enrichment (up to 35%) in corn-derived C than either the whole soil or the microorganic matter (<50 {micro}m), indicating that these pools are important recipients of plant residue inputs. Nevertheless, the microorganic matter was also a significant sink for C input, acounting for {approx}50% of the total corn-derived C remaining in the surface (0-8 cm) soil. Under the conditions of this study, tillage practices influenced the vertical distribution of SOM and corn residues but had no detectable effect on SOM turnover and on the fate of corn residues when the whole Ap horizon was considered.
  • Authors:
    • Schepers, JS
    • Havlin, JL
    • Rice, CW
  • Source: Fertilizer research
  • Volume: 42
  • Issue: 1-3
  • Year: 1995
  • Summary: The objective of a rational N fertilization program is to account for the sources and fate of N while estimating crop N needs. Efficiency of N use will vary with cropping systems and N sources. Management technologies that affect N use efficiency include the amount of N applied, timing and placement of N fertilizer, and use of inhibitors. One of the main problems in making a fertilizer N recommendation is to account for the contribution of N mineralization to plant available N. Most laboratory procedures do not account for the environmental factors that affect N mineralization and only estimate the size of the mineralizable N pool. However, changes in soil moisture and temperature can dramatically affect the amount and rate of release of mineralized N. Field and modeling techniques are two possible techniques to estimate N mineralization. Field techniques can be divided into soil and plant approaches. Soil incubations in the field provide a quantitative approach while soil nitrate tests during the growing season provide a qualitative approach to estimating N mineralization. The plant is the ultimate integrator of N mineralization. Plant N uptake by an unfertilized crop can provide a quantitative approach with certain precautions. This approach may be costly, labor intensive, and site specific. Crop N uptake during the growing season can be estimated by measuring the tissue N content or using a chlorophyll meter. The chlorophyll meter measures the greenness of the plant and has been shown to be positively correlated to plant N status. Modeling may provide another option by including the factors that affect the rate of N mineralization from a known pool. The two most important variables include soil moisture and temperature. Realistic yield expectations and accounting for existing and projected amounts of available N can improve the accuracy of N recommendations.
  • Authors:
    • Coady, S. A.
    • Clark, R. T.
    • Schneekloth, J. P.
    • Klocke, N. L.
    • Hergert, G. W.
  • Source: Journal of Production Agriculture
  • Volume: 8
  • Issue: 3
  • Year: 1995
  • Summary: Declining groundwater levels in parts of the Great Plains could lead to reduced irrigation and a decline in the economies of those areas. Improved irrigation efficiency has helped slow the rate of decline in aquifer levels but adoption of limited irrigation and water conserving rotations could slow the decline even more. The objective was to estimate the riskiness and profitability of these alternatives with and without farm commodity programs. Three water levels-rainfed, limited irrigation (6 in./yr water allocation) and full irrigation (meet crop evapotranspiration demands) were established for continuous corn (Zea mays L.), winter wheat (Triticum aestivum L.)-corn-soybean [Glycine max (L.) Merr.], and corn-soybean rotations. The profitability of each rotation under each water level was estimated using results of field experiments conducted since 1981 in west central Nebraska and cost estimates based on a typical center pivot irrigation system covering 126 acres. Stochastic dominance techniques were then applied to the data by using combinations of prices for corn, wheat, and soybean to generate cumulative distribution functions. Profitability and riskiness were estimated with and without participation in the wheat and feed grain programs and with alternate acreage conservation reserve (ACR) levels. Results showed that the government program improved income levels and reduced income variation for each water level and all rotations. Program participation did encourage monoculture corn under full irrigation and under limited irrigation with low ACR requirements. Under rainfed conditions the relative ranking of the three rotations was not changed by program participation.
  • Authors:
    • Ghaffarzadeh, M.
    • Cruse, R. M.
    • Robinson, C. A.
  • Source: Soil Science Society of America Journal
  • Volume: 60
  • Issue: 1
  • Year: 1994
  • Summary: Time, fertilizer, tillage, and cropping systems may alter soil organic carbon (SOC) levels. Our objective was to determine the effect of long-term cropping systems and fertility treatments on SOC. Five rotations and two N fertility levels at three Iowa sites (Kanawha, Nashua, and Sutherland) maintained for 12 to 36 yr were evaluated. A 75-yr continuous corn (Zea mays L.) site (Ames) with a 40-yr N-P-K rate study also was evaluated. Soils were Typic and Aquic Hapludolls and Typic Haplaquolls. Four-year rotations consisting of corn, oat (Avena sativa L.), and meadow (alfalfa [Medicago sativa L.], or alfalfa and red clover [Trifolium pratense L.]) had the highest SOC (Kanawha, 32.1 g/kg; Nashua, 21.9 g/kg; Sutherland, 27.9 g/kg). Corn silage treatments (Nashua, [≤] 18.9 g/kg; Sutherland, [≤]23.2 g/kg) and no-fertilizer treatments (Kanawha, 25.3 g/kg; Nashua, [≤]20.9 g/kg; Sutherland, [≤]23.5 g/kg) had the lowest SOC. A corn-oat-meadow-meadow rotation maintained initial SOC (27.9 g/kg) after 34 yr at Sutherland. Continuous corn resulted in loss of 30% of SOC during 35 yr of manure and lime treatments. SOC increased 22% when N-P-K treatments were imposed. Fertilizer N, initial SOC levels, and previous management affected current SOC levels. Residue additions were linearly related to SOC (Ames, r2 = 0.40; Nashua, r2 = 0.82; Sutherland, r2 = 0.89). All systems had 22 to 49% less SOC than adjacent fence rows. Changing cropping systems to those that conserve SOC could sequester as much as 30% of C released since cropping began, thereby increasing SOC.
  • Authors:
    • Fausey, N. R.
    • Mahboubi, A. A.
    • Lal, R.
  • Source: Soil Science Society of America Journal
  • Volume: 58
  • Issue: 2
  • Year: 1994
  • Summary: Sustainable use of soil resources can be assessed from management-induced changes in soil properties from long-term experiments. Such data are scanty, especially with regard to changes in soil physical properties. Therefore, soil physical and chemical analyses were performed 28 yr after initiating a crop rotation-tillage experiment on a well-drained Wooster silt loam soil (fine-loamy, mixed, mesic Typic Fragiudalf) at Wooster, OH. All combinations of three rotations (continuous corn [CC; Zea mays L.]; corn and soybean [Glycine mar (L.) Merr.] in a 2-yr rotation [CS]; and corn, oat [Avena sativa L.], and meadow in a 3-yr rotation [COM]) and of three tillage treatments (no-tillage [NT]; chisel plow [CP]; and moldboard plow [MP]) were maintained on the same plots for the entire length of study. All crops were grown every year. Soil properties studied for the 0- to 15-cm layer were: structural stability of aggregates, bulk density, total porosity, penetration resistance, organic C, pH, cation-exchange capacity (CEC), and exchangeable K, Ca and Mg. Mean bulk densities measured prior to tillage treatments and planting were 1.18, 1.24, and 1.28 Mg m-3 for CC, CS, and COM rotations, respectively. The lowest bulk density was observed for the CC-NT combination. Total aggregation in CS was 26.9% greater than CC and 111.2% greater than COM. With tillage treatments, aggregation was in the order of NT>CP>MP. Rotation treatments had no effect on aggregate size. In accord with bulk density, the relative magnitude of organic C content was 100, 85, and 63 for CC, CS, and COM rotations, respectively.