• Authors:
    • Peinemann, N.
    • Buschiazzo, D. E.
    • Dí­az-Zorita, M.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 2
  • Year: 1999
  • Summary: Crop productivity under dryland conditions is largely limited by soil water availability. Soil organic matter (SOM) contents have been found to be a reliable index of crop productivity in semiarid regions because it positively affects soil water-holding capacity. Our objectives were to explain differences in wheat (Triticum aestivum L.) yields in response to SOM levels and related properties and to quantify the contribution of a unit increment of SOM content to soil productivity during 1991,1992, and 1994 on a total of 134 production fields in the semiarid Argentine Pampas. Wheat yields were related to both soil water retention and total organic C (TOC) contents in the top layers (0-20 cm) in years with low moisture availability (1992 [r = 0.51, P < 0.01] and 1994 [r = 0.59, P < 0.01]), and were related to both total N and available P contents in a year without water deficit stress (1991 [r = 0.58, P < 0.01]). Wheat yields over all years were linearly related to TOC (r = 0.68, P < 0.01) when these contents were <17.5 g kg-. Dependence of wheat yields on soil water retention and on TOC contents under water deficit was related to the positive effect of these soil components on plant-available water. In the absence of water deficit (1991), nutrient availability was the limiting factor. Losses of 1 Mg SOM ha- were associated with a decrease in wheat yield of approximately 40 kg ha-. These results demonstrate the importance of using cultural practices that minimize losses of soil organic C in the semiarid Argentine Pampas.
  • Authors:
    • Gerard, C. J.
    • Choudhary, M.
    • Bordovsky, D. G.
  • Source: Soil Science
  • Volume: 164
  • Issue: 5
  • Year: 1999
  • Summary: In the Texas Rolling Plains, low rainfall results in low crop residue production and low soil organic matter. Low soil organic matter, coupled with low levels of silt and clay, give soils poor structure. An 11-year (1979-1989) field experiment was conducted to determine the effects of tillage (reduced vs. conventional), cropping, and residue management (with residue vs. without residue) on soil properties under dryland and irrigated systems. Cropping included a grain sorghum (Sorghum bicolor (L.) Moench.) and wheat (Triticum aestivum L.) monoculture and doublecropped, reduced tillage wheat-grain sorghum under irrigation only. Surface soil organic matter in plots with irrigated grain sorghum and wheat increased with time. Reduced-tillage irrigated grain sorghum and wheat, and especially reduced-tillage, double-cropped grain sorghum and wheat plots, had significantly higher organic matter content than conventional-tillage grain sorghum and wheat plots. Bulk density under the reduced tillage system was higher than with the conventional tillage system. However, saturated hydraulic conductivity (Ks) of the surface soil was increased by reduced tillage practices compared with conventional tillage. This may have been attributable to higher amounts of microaggregates and larger macropores under the reduced tillage system. Residue removal decreased the Ks of surface soil, especially in reduced-tillage grain sorghum and wheat plots. Microaggregation values were higher with residue retained than with residue removed (27.1 vs. 23.5 g kg-1 in dryland and 32.3 vs. 27.1 g kg-1 in irrigation). Results indicate that residue removal from Rolling Plains soils should be discouraged. Because of higher bulk density, use of a reduced tillage system may result in the need for occasional deep chiseling to reduce the effects of compaction.
  • Authors:
    • Bowman, R. A.
    • Halvorson, A. D.
  • Source: Soil Science
  • Volume: 163
  • Issue: 3
  • Year: 1998
  • Summary: Intensively cropped dryland systems in the central Great Plains require adequate N fertilization for optimum residue and grain production. However, this N fertilization could be slowly changing the chemistry of the surface soil because of a decrease in soil pH and an increase in soil organic matter (SOM) and basic cations, even in previously well buffered calcareous soil systems. We investigated the effects of five increasing ammonium-N fertilizer rates in a Platner loam, on physical and chemical changes at the 0 to 5, and 0 to 15-cm depths after three cycles of no-till wheat (Triticum aestivum L.)-corn (Zea mays L.)-fallow rotation. The measured soil pH, texture, bulk density, cation exchange capacity (CEC), total P, soluble and total soil organic carbon (SOC), nitrate-N to a depth of 60 cm, and grain yields. No significant changes were found with soil texture, bulk densities, CEC, and total P. The data showed a significant reduction in surface (0-5 cm) soil pH (6.5 to 5.1) with the highest N rate (112 kg/ha), but this was accompanied by a 40% increase in SOC. Although there were significant increases in Al and Mn and decreases in Ca concentrations in the surface 0 to 5 cm at the highest N rate, no reduction in grain yields occurred relative to lower N levels with near neutral pHs. Because only a shallow depth of the soil was affected, residue, SOM, and rapid root growth could be compensating for surface acidity, Over the longer term, we need to monitor the effects of ammoniacal-N on downward soil acidity and yield trends under these new intensive cropping systems.
  • Authors:
    • Lyon, D. J.
    • Tanaka, D. L.
    • Jones, O. R.
    • Havlin, J. L.
    • Halvorson, A. D.
    • Peterson, G. A.
    • Pennock, D. J.
  • Source: Soil & Tillage Research
  • Volume: 47
  • Issue: 3
  • Year: 1998
  • Summary: Concern about soil organic matter losses as a result of cultivation has been voiced consistently since the early part of the 20th century. Scientists working in the U.S. Great Plains recognized that organic matter losses from an already small pool could have major negative consequences on soil physical properties and N supplying capacity. The advent of reduced- and no-till systems has greatly improved our ability to capture and retain precipitation in the soil during the non-crop periods of the cropping cycle, and has made it possible to reduce fallow frequency and intensify cropping systems. The purpose of this paper is to summarize the effects of reduced tillage and cropping system intensification on C storage in soils using data from experiments in North Dakota, Nebraska, Kansas, Colorado, and Texas. Decades of farming with the wheat (Triticum aestivum L.)-fallow system, the dominant farming system in the Great Plains, have accentuated soil C losses. More intensive cropping systems, made possible by the greater water conservation associated with no-till practices, have produced more grain, produced more crop residue and allowed more of it to remain on the soil surface. Combined with less soil disturbance in reduced- and no-till systems, intensive cropping has increased C storage in the soil. We also conclude that the effects of cropping system intensification on soil C should not be investigated independent of residue C still on the surface. There are many unknowns regarding how rapidly changes in soil C will occur when tillage and cropping systems are changed, but the data summarized in this paper indicate that in the surface 2.5 cm of soil, changes can be detected within 10 years. It is imperative that we continue long-term experiments to evaluate rates of change over an extended period. It is also apparent that we should include residue C, both on the surface of the soil and within the surface 2.5 cm, in our system C budgets if we are to accurately depict residue±soil C system status. The accounting of soil C must be done on a mass basis rather than on a concentration basis.
  • Authors:
    • Schad, P.
  • Source: Forstwissenschaftliches Centralblatt vereinigt mit Tharandter forstliches Jahrbuch
  • Volume: 117
  • Issue: 3
  • Year: 1998
  • Summary: This paper discusses the agricultural system in the Charazani region in the Bolivian Eastern Cordillera. The zone from 2800 m to 4300 m asl is intensively used by Indian people and a small Mestizo group. Their traditional agriculture reflects both Indian and Spanish (16th century) traditions. Such traditional systems have been subject to rather contrary myths: some call them primitive, others ecologically adapted. Studying key variables of soil fertility (concentrations and contents (pools) of organic carbon and utilizable water storage capacities) we will investigate the degree of ecological adaptation of the soil-use system in the Charazani region. These parameters, studied in 110 field sequences covering 0-30 cm soil depth, are discussed according to their absolute levels, differences between semi-natural and agriculturally used areas, and (only for organic carbon contents) actual changes during continuous management. The results show that land-use on the dry, wind-exposed and nor irrigated sites is often insufficiently ecologically adapted. Here, intensive crop farming and sheep pasture without protection against wind erosion result in low and even decreasing soil fertility. Good ecological adaptation according to the investigated parameters is to be found, by contrast, on the more humid and better wind-protected sites as well as on the irrigated areas.
  • Authors:
    • Peterson, G. A.
    • Westfall, D. G.
    • McGee, E. A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 52
  • Issue: 2
  • Year: 1997
  • Summary: Wheat-fallow (W-F) is the predominant cropping system in the Great Plains, but the percent of precipitation stored as soil water (WSE) during fallow is frequently less than 25% with conventional tillage. No-till technology has improved potential WSE. Our objectives were to determine the effects of cropping system, landscape position (soil), and evaporative gradient (location) on WSE during inter-crop periods in intensified no-till cropping systems. Water storage efficiency was 48% during the wheat to corn fallow period in the 3- or 4-year rotational systems, contrasting sharply with the 22% WSE for the W-F system. The 3-year system, with a shorter fallow period (11 months), was just as effective in storing water as the long fallow period (14 months) in the WF system. Water storage efficiency was the lowest at the southern location, which had the highest potential evapotranspiration, but the contrasts among cropping systems remained. Toeslope soils had the highest WSE compared to summit or sideslope positions because of their opportunity to catch runoff water. The possibility exists for using even move intensive cropping systems than those examined in this study and this may mean that summer fallow could be eliminated with no-till practices.
  • Authors:
    • Norwood, C.
    • Currie, R.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 1
  • Year: 1997
  • Summary: Dryland crop yields in the U.S. Great Plains are limited by low precipitation and high potential evapotranspiration. In western Kansas wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are grown commonly, whereas corn (Zea mays L.) is believed to lack sufficient drought and heat tolerance for dryland production. A study was conducted near Garden City, KS, from 1991 through 1995 to determine whether corn could be grown successfully. No-till (NT) and conventional-till (CT) corn and grain sorghum were compared. In the driest year, sorghum yielded 137% more than corn with CT and 85% more with NT, but in 3 of 5 yr, NT corn yielded from 34% to 112% more than NT sorghum. In the remaining year, CT sorghum yielded more than CT corn, but NT yields did not differ. Overall, NT increased corn yields by 28% and net return by 69%, but increased sorghum yields by only 11% add had no effect on net return. No-till corn yielded 28% more than NT sorghum and produced 169% more net return, whereas CT corn yielded 11% more than CT sorghum and produced 48% more net return. Dryland corn can be grown in western Kansas if lower yields and returns are accepted in dry years in exchange for yields and returns considerably higher than those of sorghum in favorable years. No tillage will substantially increase yields in most years and is essential to assure adequate corn yields in dry years.
  • Authors:
    • Papendick, R.
    • Parr, J.
  • Source: Annals of Arid Zone
  • Volume: 36
  • Issue: 3
  • Year: 1997
  • Summary: Most dryland fanning systems depend an tillage to grow crops. There is overwhelming evidence that repeated tillage is destroying the soil resource base and causing adverse environmental impacts. Tillage degrades the fertility of soils, causes air and water pollution, intensifies drought stress, destroys wildlife habitat, wastes fuel energy, and contributes to global warming. Consequently, most tillage-based systems in a dryland environment are not sustainable in the long-term. Today, dryland farmers are expected to produce food in ever greater quantities. This is becoming more difficult to do in view of declining soil quality, most of which is caused by soil tillage. It is becoming well documented scientifically that continuous no-till is the most effective, and practical approach for restoring and improving soil quality which is vital for sustained food production and a healthy environment. With this way of farming crop, residues or other organic amendments are retained on the soil surface and sowing/fertilizing is done with minimal soil disturbance. Research and farmers' experience indicate that with continuous no-till soil organic matter increases, soil structure improves, soil erosion is controlled, and in time crop yields increase substantially from what they were under tillage management, due to improved water relations and nutrient availability. These changes help to promote a cleaner and healthier environment and a more sustainable agriculture. A major obstacle that farmers often face with change to continuous no-till is overcoming yield-limiting factors during the transition years, that is, the first years of no-till following a history of intensive conventional tillage. These factors are often poorly understood and may be biologically-driven. Some of the problems involve residue management and increased weed and disease infestations. Farmer experience seems to indicate that many problems during the transition are temporary and become less important as the no-till system matures and equilibrates. The judicious use of crop rotations, cover crops and same soil disturbance may help reduce agronomic risks during the transition years. Farmers switching to continuous no-till must often seek new knowledge and develop new skills and techniques in order to achieve success with this new and different way of farming. Answers to their questions are urgently needed to provide strategies far promoting no-till as a way to enhance agricultural sustainability for future generations.
  • Authors:
    • Unger, P. W.
    • Alemu, G.
    • Jones, O. R.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 28
  • Issue: 1-2
  • Year: 1997
  • Summary: Soil and water conserving practices must be used to sustain dryland crop production in semiarid regions. In this 1994 study, we evaluated the effects of different cropping system and tillage method treatments on surface residue cover, organic matter content, aggregation, and water infiltration for a soil used for grain sorghum [Sorghum bicolor (L.) Moench] production in the United States Southern Great Plains from 1982 to 1994. Cropping systems were continuous sorghum (CS) and winter wheat (Triticum aestivum L.)-fallow-grain sorghum-fallow (designated WSF) and tillage methods were no-tillage (NT) and stubble mulch tillage (SMT). Treatments were CS-NT, CS-SMT, WSF-NT, and WSF-SMT. Surface residue cover before planting sorghum was >70% with CS-NT and WSF-NT, 29% with CS-SMT, and 12% with WSF-SMT. Surface cover after planting was approximate to 50% with both NT treatments, whereas amounts with other treatments were similar to those before planting. Soil organic matter contents (0- to 10-cm depth) were greater on CS than on WSF plots, but were not affected by tillage method in either cropping system. Water stable aggregation (0- to 2-cm depth) was greater with SMT than with NT in both cropping systems, but differences between cropping systems were not significant. Dry aggregates were smaller with NT than with SMT. Water infiltration was or tended to be greater on CS than on WSF plots, apparently because the WSF plots contained more water when infiltration was measured. Infiltration was not affected by tillage method, apparently because the greater amount of surface residues on NT plots counteracted the less water stable aggregates and smaller dry aggregates that had potential for reducing infiltration on the NT plots. This study indicates that no cropping system-tillage method combination treatment had a consistently beneficial or detrimental effect on soil conditions. In conclusion, both cropping systems (CS and WSF) and both tillage methods (NT and SMT) are suitable for conserving soil and water resources and, therefore, for sustaining dryland crop production in the semiarid United States Southern Great Plains.
  • Authors:
    • Merrill, S. D.
    • Black, A. L.
    • Bauer, A.
  • Source: Soil Science Society of America Journal
  • Volume: 60
  • Issue: 2
  • Year: 1996
  • Summary: In dryland cropping, no-tillage ran increase small grain crop growth compared with conventional tillage. Because root systems develop ahead of aboveground growth and are affected by soil environment, observation of root growth will show the mechanisms by which no-till enhances crop growth. Wheat (Triticum aestivum L.) was grown in a spring wheat-winter wheat-sunflower (Helianthus annus L.) rotation begun in 1984 on Temvik-aWilton silt loam (fine-loamy, mixed TS pic and Pachic Haploborolls) under conventional till (CT: spring dishing), minimal till (hlT: spring undercutting) and no-till (NT). Root length growth OULG) was measured by microvideo camera in pressurized-wall minirhizotrons, and soil water was measured by neutron moisture meter. Relative to CT, NT generally enhanced RLG more than aboveground growth; RLG averaged 65, 130, and 145 km/cm(2) in 1988, 1989, and 1990, respectively. In 1988, RLG was 37% greater than hlT (P < 0.1), with CT intermediate. In 1989, RLG was 40% greater in NT than in CT, with ILIT intermediate, and RLG in 1990 was 112% greater in NT than CT (no MT). Final biomass averaged 380, 1730, and 3090 kg/ha in 1988 through 1990, and was 36% greater, not significantly different, and 44% greater in NT than CT, respectively. Root penetration was shallow (1.1 m or less) in dry subsoil, but in each year roots penetrated to greater soil depths under NT than under hlT or CT. Amounts of stored soil water were generally not significantly different among tillages, but more water was depleted in 1990 under NT than CT. Cooler soil under NT (measured in 1989) and superior soil water conservation in the near-surface zone appear to confer a root growth advantage to the NT treatment.