• Authors:
    • Shea, K. L.
    • Gregory, M. M.
    • Bakko, E. B.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 20
  • Issue: 2
  • Year: 2005
  • Summary: We compared soil characteristics, runoff water quantity and nutrient fluxes, energy use and productivity of three farm types in an unusually dry farming season: conventional (continuous corn and deep tillage), rotation (5-year corn-soybean-oats/ alfalfa-alfalfa-alfalfa rotation with tillage 2/5 years) and no-till (corn-soybean with no cultivation). Soil organic matter content was highest on the rotation farm, followed by the no-till farm, and lowest on the conventional farm. Nitrate content of the soil did not differ significantly among the three farms, although the conventional farm had a much higher input of fertilizer nitrogen. Soil penetrometer resistance was lower and percent soil moisture was higher in the no-till and rotation systems compared to the conventional farm. Soil macroinvertebrate abundance and diversity were highest on the no-till farm, followed by the rotation farm. No invertebrates were found in the soil of the conventional farm. The conventional farm had the highest runoff volume per cm rain and higher nitrogen (N) loss in runoff when compared to the rotation and no-till farms, as well as a higher phosphorus (P) flux in comparison to the no-till farm. These results indicate that perennial close-seeded crops (such as alfalfa) used in crop rotations, as well as plant residue left on the surface of no-till fields, can enhance soil organic content and decrease runoff. The lower soil penetrometer resistance and higher soil moisture on the rotation and no-till farms show that conservation tillage can increase soil aggregation and water infiltration, both of which prevent erosion. Furthermore, crop rotation, and particularly no-till, promote diverse invertebrate populations, which play an important role in maintaining nutrient cycling and soil structure. Crop rotation and no-till agriculture are less fossil-fuel intensive than conventional agriculture, due to decreased use of fertilizers, pesticides and fuel. In this unusually dry year they provided superior corn and soybean yields, most likely due to higher soil moisture as a result of greater water infiltration and retention associated with cover crops (rotation farm) and crop residue (no-till farm).
  • Authors:
    • Ahmad, R.
    • Jabbar, A.
    • Ehsanullah
    • Nazir, M. S.
  • Source: Pakistan Journal of Agricultural Sciences
  • Volume: 42
  • Issue: 1/2
  • Year: 2005
  • Summary: A field experiment was conducted during 1998/99 and 1999/2000 to evaluate the performance of diversified rice-based relay cropping systems at zero and conventional tillage under strip plantation on a sandy clay loam soil in Faisalabad, Pakistan. The treatments comprised rice/fallow and rice intercropped with wheat, barley, forage oats, gram [ Cicer arietinum], lentil, linseed, fenugreek, sunflower, rape, forage maize and Egyptian clover [ Trifolium alexandrinum]. All rice-based relay cropping were more productive and economically viable than rice/fallow. However, rice intercropped with grain or forage legumes (such as fenugreek, gram, lentil and Egyptian clover) were more superior to that intercropped with non-legumes (such as wheat, barley, forage oats, rape, sunflower and forage maize) in terms of sustainability, total rice grain yield equivalent (TRGYE) and net field benefits under both zero and conventional tillage. Rice/fenugreek relay cropping recorded the highest TRGYEs of 7.48 and 9.27 t/ha and net monetary gains of Rs. 40 620 and 45 120/ha under zero and conventional tillage, respectively.
  • Authors:
    • Ewulo, B. S.
    • Agele, S. O.
    • Oyewusi, I. K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 72
  • Issue: 2
  • Year: 2005
  • Summary: The interaction of land use and seasonal microclimatic events could explain the differences in soil quality characteristics which mediate biological and physical processes of the soil under low input land use systems (plough plus harrow, strip/heap tillage, manual clearing/no till). It is hypothesised that in a humid tropical Alfisol, low input system involving reduced tillage methods, and mineral fertilizer and/or livestock manure use, would support a higher density of microbial biomass, soil aggregation, organic C and total N and hence improvement in soil quality. The dynamics of biotic and abiotic soil properties as affected by methods of seedbed preparation characterised by manural input and microclimatic transitions from wet to dry season was studied in a maize field in a tropical rain forest Alfisol in Akure, a humid rain forest zone of Nigeria. Each year, trials were carried out during the rainy (April-July) and late (September-December) seasons of 2001 and 2002. Methods of seedbed preparation involving plough plus harrow, strip/heap tillage and no tillage, and addition of different gradients of manures (mineral N and/or plant debris and live stock litter) were imposed on the soil at the site of the experiment (of comparable physical properties of bulk density and texture). Among the treatments, there were significant differences in the values of water holding capacity, aggregate stability (macro-aggregation), concentrations of microbial biomass, organic C, total and mineral N and CEC. In the rainy and late season trials, the strip/heap tillage and the no till treatments improved aggregate stability (as measured by the percent ages of aggregates between 2 and 10 mm of soil) and water holding capacity over plough+harrow. For example, in the rainy season trial, under treatments involving strip/heap tillage and the no till alone and in combination with livestock manuring and residue retention, the values of aggregates between 2 and 10 mm range from (110-116; 113-119 g/kg) and water holding capacity (0.11-0.14; 0.12-0.15 g/g) over plough+harrow (107.3 g/kg; 0.11 g/g). Similar trends were found in the values of soil microbial biomass C (377, 353; 547, 490 g/g dry soil), soil organic C (3.8, 4.3; 5.2, 5.5 g/g) and total N (2.9, 2.3; 2.9, 3.0 mg/g) for strip/heap and no till treatments compared to plough+harrow (327.6 g/g dry soil; 3.4 g/g; 2.8 mg/g). Although the %C microbial to C organic ratio (an indicator of the utilisation of organic carbon by the microbesin terms of organic matter turn over rate) was stable for all treatments, its magnitude was not constant but increased with increases in soil C concentration. The values of microbial biomass carbon to organic carbon (Cmic: Corg) ratio were higher under ploughing and heap tillage combined with mineral N (0.096, 0.099) than in no-till treatment (0.083) in the rainy season trial. Similar trends were obtained in the magnitudes of this parameter in the late season trial. Microbial biomass correlated positively with both soil organic C ( y=0.393 c-6.7; r2=0.99; P< 0.05)
  • Authors:
    • Trein, C.
    • Herzog, R.
    • Levien, R.
  • Source: Engenharia Agricola
  • Volume: 24
  • Issue: 3
  • Year: 2004
  • Summary: To evaluate soyabean productivity on natural pasture fields, grown once with oats to produce grain and straw for soil cover, an experiment was conducted on a Typic Paleudult Soil in Eldorado do Sul, Rio Grande do Sul, Brazil. After mechanically harvesting oats, the straw was returned to plots in amounts of 0, 2, 3, 4, 5 and 6 mg/ha and were divided according to the furrow opening depth (0.06 and 0.12 m). The area was divided in 2, with and without irrigation. The volume of soil mobilized by the fertilizer furrow openers was 53% higher when the working depth reached 0.12 m compared to 0.06 m, but no difference due to the amount of cover crop residues was attained. Grain yield, crop biomass and root mass up to 0.15 cm depth did not differ with both soil working depth and crop residue cover. Irrigation increased grain yield and total biomass of soyabeans. Even without irrigation, soyabean productivity was higher than the Rio Grande do Sul State average, showing its suitability to be grown on native pastures under the no-till system.
  • Authors:
    • Peterson, G. A.
    • Westfall, D. G.
  • Source: Annals of Applied Biology
  • Volume: 144
  • Issue: 2
  • Year: 2004
  • Summary: In the Great Plains of North America potential evaporation exceeds precipitation during most months of the year. About 75% of the annual precipitation is received from April through September, and is accompanied by high temperatures and low relative humidity. Dryland agriculture in the Great Plains has depended on wheat production in a wheat-fallow agroecosystern (one crop year followed by a fallow year). Historically this system has used mechanical weed control practices during the fallow period, which leaves essentially no crop residue cover for protection against soil erosion and greatly accelerates soil organic carbon oxidation. This paper reviews the progress made in precipitation management in the North American Great Plains and synthesises data from an existing long-term experiment to demonstrate the management principles involved. The long-term experiment was established in 1985 to identify dryland crop and soil management systems that would maximize precipitation use efficiency (maximization of biomass production per unit of precipitation received), improve soil productivity, and increase economic return to the farmers in the West Central portion of the Great Plains. Embedded within the primary objective are subobjectives that focus on reducing the amount of summer fallow time and reversing the soil degradation that has occurred in the wheat-fallow cropping system. The experiment consists of four variables: 1) Climate regime; 2) Soils; 3) Management systems; and 4) Time. The climate variable is based on three levels of potential evapotranspiration (ET), which are represented by three sites in eastern Colorado. All sites have annual long-term precipitation averages of approximately 400-450 mm, but vary in growing season open pan evaporation from 1600 mm in the north to 1975 mm in the south. The soil variable is represented by a catenary sequence of soils at each site. Management systems, the third variable, differ in the amount of summer fallow time and emphasize increased crop diversity. All systems are managed with no-till techniques. The fourth variable is time, and the results presented in this paper are for the first 12 yr (3 cycles of the 4-yr system). Comparing yields of cropping systems that differ in cycle length and systems that contain fallow periods, when no crop is produced, is done with a technique called "annualisation". Yields are "annualised" by summing yields for all crops in the system and dividing by the total number of years in the system cycle. For example in a wheat-fallow system the wheat yield is divided by two because it takes 2 yr to produce one crop. Cropping system intensification increased annualised grain and crop residue yields by 75 to 100% compared to wheat-fallow. Net return to farmers increased by 25% to 45% compared to wheat-fallow. Intensified cropping systems increased soil organic C content by 875 and 1400 kg ha(-1), respectively, after 12 yr compared to the wheat-fallow system. All cropping system effects were independent of climate and soil gradients, meaning that the potential for C sequestration exists in all combinations of climates and soils. Soil C gains were directly correlated to the amount of crop residue C returned to the soil. Improved macroaggregation was also associated with increases in the C content of the aggregates. Soil bulk density was reduced by 0.01g cm(-1) for each 1000 kg ha(-1) of residue addition over the 12-yr period, and each 1000 kg ha(-1) of residue addition increased effective porosity by 0.3%. No-till practices have made it possible to increase cropping intensification beyond the traditional wheat-fallow system and in turn water-use efficiency has increased by 30% in West Central Great Plains agroecosystems. Cropping intensification has also provided positive feedbacks to soil productivity via the increased amounts of crop residue being returned to the soil.
  • Authors:
    • Rogers, G. S.
    • Little, S. A.
    • Silcock, S. J.
    • Williams, L. F.
  • Source: Acta Horticulturae
  • Issue: 638
  • Year: 2004
  • Summary: A no-till system using permanent beds, permanent subsurface irrigation and organic mulches grown in situ was implemented as an alternative to conventional production in an experiment conducted in North Queensland, Australia. The system used a tropical legume, Centrosema pubescens 'Cavalcade', or the C 4 grasses Bothriochloa pertusa 'Keppel' or 'Hatch' as cover crops over summer and autumn. Cover crops were killed using glyphosate (1440 g a.i./ha) and residues were left on the soil surface. Vegetable seedlings were then planted through the mulch residues and grown using conventional agronomic techniques. Following harvest, crop residues were macerated and the following cover crop direct sown through the mulch residues. Soil from conventional production areas using polyethylene mulch had significantly lower aggregate stability than all other treatments. Soil aggregates taken from beneath cover crop mulches were more stable than aggregates under polyethylene mulch after one year under the no-till regime. Soil aggregates after three years of treatment showed similar statistical differences between the treatments. Bulk density in permanent beds under C. pubescens mulch was significantly lower than uncultivated bare soil and frequently cultivated polyethylene mulch. Soil under frequent cultivation was significantly more compacted than uncultivated bare soil. There were significantly more earthworms under C. pubescens and B. pertusa mulch than in uncultivated bare topsoil or under polyethylene mulch. No earthworms were found in any sample under polyethylene mulch. The yields of tomatoes after 5 harvests were not significantly different for conventional and no-till production.
  • Authors:
    • Halvorson, A. D.
    • DeVuyst, E. A.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 1
  • Year: 2004
  • Summary: Annualized yields with more intensive cropping (IQ systems tend to be greater than those of spring wheat-fallow (SW-F); however, little economic comparison information is available. The long-term (12 yr) effects of tillage system and N fertilization on the economic returns from two dryland cropping systems in North Dakota were evaluated. An IC rotation [spring wheat (Triticum aestivum L.)winter wheat (T. aestivum L.)-sunflower (Helianthus annuus L.)] and a 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 IC system and 0, 22, and 45 kg N ha(-1) for the SW-F system. Annual precipitation ranged from 206 to 655 mm, averaging 422 mm over 12 yr. The IC system generated higher profits than the SW-F system, but the IC profits were more variable. Within the IC system, MT generated higher profits than corresponding N treatments under CT and NT, but MT profits were more variable. Of the N rates evaluated, the largest N rates generated the largest profits. The dryland IC system with MT and NT was more profitable than the best SW-F system using CT for this location. Stochastic dominance analyses revealed that the SW-F system and IC system CT treatments were economically inefficient when compared with the IC system with MT and NT.
  • Authors:
    • Gibson, S. G.
    • Yarboro, W.
    • Hamrick, M.
    • Thompson, S.
    • King, R.
  • Source: Proceedings of the 26th Southern Conservation Tillage Conference for Sustainable Agriculture
  • Year: 2004
  • Summary: In addition to regular programming, County Agricultural Extension agents are asked many times to respond to questions, suggestions and concerns by their farmer clientele. In North Carolina as in other states an advisory leadership system is in place and farmers can formally and informally make suggestions and requests for on-farm demonstrational work. In many cases what the farmers are observing in their fields and/or things they have read "spark" the interactions with agents. Such has been the case in Cleveland County, NC. For example in the early continuous no-till era many area farmers were concerned about soil compaction. Measurements and simple demonstrations conducted by the Cleveland and Lincoln County agents and supported by the NCSU Soil Science Department and Cleveland County Government helped alleviate these concerns. Later as fields were in continuous no-till for 5 or more years, farmers began to notice a greater than expected development of their crops prior to major applications of fertilizer nitrogen. These observations led to a replicated test in wheat conducted by the Cleveland County Agricultural Extension agent comparing a field in a 2 year no-till wheat soybean rotation verses a nearby field in a 5 year continuous no-till wheat soybean rotation. Also a 6 year replicated test was initiated on Cleveland County owned land that had been in continuous no-till for 10 years. The test was set up as a continuous soybean corn rotation and in addition to the standard dryland portion, irrigation was used in part of the study to simulate a "good" corn year. Five nitrogen rates were used. The economics of the cost of fertilizer nitrogen was used to demonstrate that the Realistic Yield Expectation (RYE) method for determining nitrogen rates was very much applicable in continuous no-till. Both the wheat and corn tests indicated that residual soil nitrogen was indeed becoming a major factor in continuous no-till for these field crops and when farmers considered the realities of the weather very likely nitrogen rates can be reduced with confidence.
  • Authors:
    • Halvorson, A. D.
    • Nielsen, D. C.
    • Reule, C. A.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 4
  • Year: 2004
  • Summary: No-till (NT) production systems, especially winter wheat (Triticum aestivum L.)-summer crop-fallow, have increased in the central Great Plains, but few N fertility studies have been conducted with these systems. Therefore, winter wheat (W) response to N fertilization in two NT dryland crop rotations, wheat-corn (Zea mays L.)-fallow (WCF) and wheat-sorghum (Sorghum bicolor L.)-fallow (WSF), on a Platner loam (fine, smectitic, mesic Aridic Palleustoll) was evaluated for 9 yr. Five N rates, 0, 28, 56, 84, and 112 kg N ha(-1), were applied to each rotation crop. Wheat biomass and grain yield response to N fertilization varied with year but not with crop rotation, increasing with N application each year, with maximum yields being obtained with 84 kg N ha(-1) over all years. Based on grain N removal, N fertilizer use efficiency (NFUE) varied with N rate and year, averaging 86, 69, 56, and 46% for the 28, 56, 84, and 112 kg ha(-1) N rates, respectively. Grain protein increased with increasing N rate. Precipitation use efficiency (PUE) increased with N addition, leveling off above 56 kg N ha(-1). A soil plus fertilizer N level of 124 to 156 kg N ha(-1) was sufficient to optimize winter wheat yields in most years in both rotations. Application of more than 84 kg N ha(-1) on this Platner loam soil, with a gravel layer below 120 cm soil depth, would more than likely increase the amount of NO3-N available for leaching and ground water contamination. Wheat growers in the central Great Plains need to apply N to optimize dryland wheat yields and improve grain quality, but need to avoid over-fertilization with N to minimize NO3-N leaching potential.
  • Authors:
    • Kaspar, T. C.
    • Parkin, T. B.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Year: 2004
  • Summary: It is well known that soil CO2 flux can exhibit pronounced day-to-day variations; however, measurements of soil CO2 flux with soil chambers typically are done only at discrete points in time. This study evaluated the impact of sampling frequency on the precision of cumulative CO2 flux estimates calculated from field measurements. Automated chambers were deployed at two sites in a no-till corn/ soybean field and operated in open system mode to measure soil CO2 fluxes every hour from 4 March 2000 through 6 June 2000. Sampling frequency effects on cumulative CO2-C flux estimation were assessed with a jackknife technique whereby the populations of measured hourly fluxes were numerically sampled at regular time intervals ranging from 1 d to 20 d, and the resulting sets of jackknife fluxes were used to calculate estimates of cumulative CO2-C flux. We observed that as sampling interval increased from 1 d to 12 d, the variance associated with cumulative flux estimates increased. However, at sampling intervals of 12 to 20 d, variances were relatively constant. Sampling once every 3 d, estimates of cumulative C loss were within +-20% of the expected value at both sites. As the time interval between sampling was increased, the potential deviation in estimated cumulative CO2 flux increased such that sampling once every 20 d yielded potential estimates within 60% and 40% of the actual cumulative CO2 flux. A stratified sampling scheme around rainfall events was also evaluated and was found to provide more precise estimates at lower sampling intensities. These results should aid investigators to develop sampling designs to minimize the effects of temporal variability on cumulative CO2-C estimation.