• Authors:
    • Powell, C.
  • Source: New South Wales Department of Agriculture
  • Year: 2000
  • Summary: Tabulated data on yield are presented from variety trials conducted in New South Wales, Australia, during 1999 for barley, rape, chickpeas, faba beans, field peas, lentils, lupins, mixed cereal (barley, oats, rye, triticale and wheat), oats, triticale and wheat.
  • Authors:
    • Olsson, K. A.
    • Cockroft, B.
  • Source: Australian Journal of Soil Research
  • Volume: 38
  • Issue: 1
  • Year: 2000
  • Summary: A study on irrigated orchards in northern Victoria, Australia, on a fine sandy loam over clayey red-brown earth showed soil hardening within 2-3 months after the initial cultivation. This common yet distinct form of soil hardening is termed coalescence. Coalescence is the slow increase in soil hardness which develops during cycles of wetting and drying. The structure of a well-prepared bed of soil that is water-stable and not trafficked changes to one that is hard, although perforated with biopores. These pores facilitate the infiltration of water, drainage, and some growth of roots, but the hard matrix causes root growth and activity to be substantially reduced compared with roots in loose soil and this reduces the productivity of the crop. Coalescence is an important cause of poor responses in productivity to zero and minimum tillage systems of soil management. Isolated examples of soils in the field that remain soft, loose, and porous, after more than 2 years since cultivation were found. This suggests that it might be possible to prevent coalescence. These coalescence-stable soils, in common with virgin soils, have properties that enable them to resist coalescing. High organic matter (>4% w/w total C content) is closely related to zero coalescence.
  • Authors:
    • Sherrod, L.
    • Ahuja, L. R.
    • Peterson, G. A.
    • Shaffer, M. J.
    • Rojas, K. W.
    • Ma, L. W.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 3
  • Year: 1999
  • Summary: Decomposition of surface crop residues is important for agricultural management, especially under conservation tillage. The objective of this study was to test several models for describing crop residue decomposition under three eastern Colorado dryland agroecosystems at Sterling, Stratton, and Walsh with a yearly mean air temperature of 9.7, 10.4, and 12.0 degrees C, respectively. At each site, a soil toposequence common to its geographic region was chosen to include a summit, a sideslope, and a toeslope position, and several crop rotations were practiced under no-till conditions. Grab samples were taken at planting and before harvesting for surface residue measurement since 1985, Simulation results showed that the Douglas-Rickman model described surface crop residue decomposition better than the Gregory model during a 13-year period, based on a normalized objective function (NOF). Our fitted decomposition rate coefficients using the Douglas-Rickman model matched those originally published. The Douglas-Rickman model, which uses a first-order decay with respect to degree-days, was further evaluated against two other first-order decay models: one using a first-order decay equation with respect to decomposition-days and the other assuming a first order decay with respect to time (d), Although the three approaches performed equally well in terms of NOF values (P = 0.354), fitted decomposition rate coefficients were significantly different (P < 0.012) among the three experiment sites when models based on decomposition-days or on time (in days) were used. Therefore, the Douglas-Rickman model may be more applicable for describing long-term crop residue decomposition because of its consistency in model parameters among experimental sites and simplicity in modeling approach.
  • Authors:
    • Schomberg, H. H.
    • Jones, O. R.
  • Source: Soil Science Society of America Journal
  • Volume: 63
  • Issue: 5
  • Year: 1999
  • Summary: Soil C and N greatly influence Long-term sustainability of agricultural systems, We hypothesized that cropping and tillage differentially influence dryland soil C and N characteristics in the Southern High Plains. A Pullman clay loam (fine, mixed, thermic Torrertic Paleustol) cropped to vc heat (Triticum aestivum L.)-sorghum [Sorghum bicolor (L) Moench]-fallow (WSF), continuous wheat (CW) and continuous sorghum (CS) under no-tillage (NT), and stubble mulch (SM) was sampled at three depths to determine soil C and N characteristics. For CW, CS, and WSF phases (F-WSF, S-WSF, W-WSF), soil organic C (SOC) averaged 10.6 to 13.1 kg m(-3) and was greatest for CW, Carbon mineralization (C-MIN) at 0 to 20 mm was 30 to 40% greater for CW and F-WSF than for CS, S-WSF, or W-WSF. Cropping system by depth influenced soil organic N (SON),vith greatest SON at 0 to 20 mm in CW (1.5 kg m(-3)). At 0 to 20 mm for SM and NT, SOC was 9.9 and 12.5 kg m(-3), soil microbial biomass C (SMBC) was 0.80 and 1.1 kg m(-3), and soil microbial biomass N (SMBN) was 0.14 and 0.11 kg m(-3). Also at 0 to 20 mm, NT had 60% greater C-MIN, 11% more SMBC as a portion SOC, and 25% more SON compared to SM. Summed for 0 to 80 mm, NT had more SOC (0.98 vs 0.85 kg m(-2)) and SON (0.10 vs 0.9 kg m(-2)) than SM, and CW had greater or equal C and N activity as other systems. Negative correlations between yield and SOC, SMBC, C-MIN, SON, and SMBN indicate N removal in grain negatively affects active and labile C and N pools. Under dryland conditions, C and N conservation is greater with NT and with winter wheat because of less soil disturbance and shorter fallow.
  • Authors:
    • Ray, D. E.
    • Slinsky, S. E.
    • Graham, R. L.
    • Becker, D. A.
    • de la Torre Ugarte, D.
    • Turhollow, A.
    • Perlack, R. L.
    • Walsh, M. E.
  • Year: 1999
  • Authors:
    • Bonfil, D. J.
    • Mufradi, I.
    • Klitman, S.
    • Asido, S.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 3
  • Year: 1999
  • Summary: Yields of dryland crops in semiarid and arid zones are limited by precipitation, and so water content and placement are very important at each stage of development. Spring wheat (Triticum aestivum L.) grown in a wheat-fallow (WF) rotation system (1 crop in 2 years) generally occupies the greatest area in the Israeli dryland region, more than the continuous wheat (CW) rotation system. To identify the optimal crop management for dryland farming where annual precipitation is <250 mm, we compared the effects of no-tillage (NT) and conventional tillage (CT) on wheat growth and water use efficiency (WUE) in both the WF and the CW rotation systems, and on water storage in fallow (F) plots. During the 4-year period from 1994 to 1997, experiments Here conducted at Gilat Experimental Station, located in the south of Israel (average annual precipitation, 237 mm; soil type, sandy loam loess-Calcic Xerosol). In the fallow year, F-NT increased water infiltration and soil water content in comparison with F-CT. However, most of the water evaporated during the summer, especially from the upper soil layer (0-120 cm). During growth, uncultivated soil with straw mulch increased water content in the upper soil layer and also encouraged the development of a longer root system capable of utilizing deeper water. During 1995, similar grain yields were obtained with both NT and CT treatments, an average of 3.45 t ha(-1) for WF and 2.9 t ha(-1) for CW. In the last 2 drought gears (1996 and 1997), NT management increased yields by 62 to 67% for WF and by 18 to 75% for CW, relative to CT management. During the 2 years when water deficiency occurred during the grain-filling stage (1994 and 1997), NT management increased grain weight by 20% and test weight by 5 to 7%, in addition to the 70 to 200% increase in the total grain yield, relative to CT management. Crop yield and WUE can be increased in arid zones with annual precipitation of < 200 mm, through use of a wheat-fallow rotation system that is managed by NT.
  • Authors:
    • Black, A. L.
    • Krupinsky, J. M.
    • Merrill, S. D.
    • Halvorson, A. D.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 4
  • Year: 1999
  • Summary: Winter wheat (Triticum aestivum L.) can add diversity to dryland crop rotations in the northern Great plains, but it is susceptible to winterkill in low surface residue environments. A 12-year study was conducted to determine the response of two winter wheat cultivars, Roughrider and Norstar; to tillage system (conventional-till, CT; minimum-till, MT: and no-till, NT) and N fertilizer rate (34, 67, and 101 kg N ha(-1)) in a dryland spring wheat-winter wheat-sunflower (Helianthus annuus L,) rotation. Grain yields were greater with MT (1968 kg ha(-1)) and NT (2022 kg ha(-1)) than with CT (1801 kg ha(-1)), but tillage system effects on grain yield varied among years, Increasing N rate from 34 kg N ha(-1) to 67 kg N ha(-1) increased grain production from 1844 to 1953 kg ha(-1), but yield response to N rate varied among years., The greatest overall grain yield (2111 kg ha(-1)) if as obtained with NT and application of 101 kg N ha(-1). Grain yields were lowest during gears when plant-available Hater (PAW) was 400 an PAW, leaf spot disease incidence was greatest, particularly at the lowest N rate with NT. Application of adequate N reduced the disease incidence in all tillage treatments. Cultivar differences Here significant 3 out of 12 years, but not consistent. Winterkill was a factor for both cultivars in only 1 year in the CT and MT plots. Winter wheat performed Hell as a rotational crop in this cropping system when using,tfT and NT systems and adequate N fertility, Our long-term results indicate that producers in the northern Great Plains ran use winter wheat successfully in annual cropping systems that do not include a fallow period, particularly if NT is used with adequate N fertilization.
  • Authors:
    • Merrill, S. D.
    • Tanaka, D. L.
    • Black, A. L.
    • Halvorson, A. D.
    • Krupinsky, J. M.
  • Source: Agronomy Journal
  • Volume: 91
  • Issue: 4
  • Year: 1999
  • Summary: Sunflower (Helianthus annuus L.) is a warm-season, intermediate water-use crop that can add diversity to dryland crop rotations, Reduced tillage systems may Enhance sunflower yield in intensive cropping systems. A 12-year study was conducted to determine how sunflower cultivars of early and medium maturity respond to tillage system (conventional-till, CT; minimum-till, MT; no-till, NT) and N fertilization (34, 67, and 101 kg N ha(-1)) within a dryland spring wheat (Triticum aestivum L.)-winter wheat-sunflower rotation. Averaged across N rates, cultivars, and years, sunflower seed yields were greater with MT (1550 kg ha(-1)) than with NT (1460 kg ha(-1)) and CT (1450 kg ha(-1)). Increasing N rate above 34 kg N ha-L generally increased gain yield, but varied from year to year. The tillage X N interaction showed that the highest seed yields were obtained with NT (1638 kg ha(-1)) and MT (1614 kg ha(-1)) at 101 kg N ha(-1). Total plant-available water (TPAW) of 500 mm did not result in increased sunflower yields over those with 350 to 500 mm TPAW. Yield differences between cultivar maturity classes varied from year to gear and with tillage and N level. At the lowest N rate, weeds were more problematic in NT than in CT and MT plots. More N fertilizer may be needed with NT to optimize sunflower yields than with CT and MT, because of less residual soil NO3-N with NT. Results indicate that producers in the northern Great Plains can use sunflower successfully in annual a cropping systems, particularly if MT and NT are used with adequate N fertilization.
  • Authors:
    • Manley, W. A.
    • Hart, R. H.
    • Manley, J. T.
    • Reeder, J. D.
    • Schuman, G. E.
  • Source: Ecological Applications
  • Volume: 9
  • Issue: 1
  • Year: 1999
  • Summary: Rangeland grazing management strategies have been developed in an effort to sustain efficient use of forage resources by livestock. However, the effects of grazing on the redistribution and cycling of carbon (C) and nitrogen (N) within the plant-soil system are not well understood. We examined the plant-soil C and N balances of a mixed grass rangeland under three livestock stocking rates using an area that had not been grazed by domestic livestock for more than 40 years. We established nongrazed exclosures and pastures subjected to continuous season-long grazing at either a light stocking rate (20 steer-days/ha) or a heavy stocking rate (59 steer-days/ha, ~50% utilization of annual production). Twelve years of grazing under these stocking rates did not change the total masses of C and N in the plant-soil (0-60 cm) system but did change the distribution of C and N among the system components, primarily via a significant increase in the masses of C and N in the root zone (0-30 cm) of the soil profile. The mass of soil C (0-60 cm) under heavy grazing was comparable to that of the light grazing treatment. Grazing at the heavy stocking rate resulted in a decrease in peak standing crop (PSC) of aboveground live phytomass, an increase in blue grama (Bouteloua gracilis [H.B.K.] Lag. Ex Steud.), and a decrease in western wheatgrass (Pascopyrum smithii [Rydb.] A. Love) compared to the light grazing treatment. The dominant species under light grazing was western wheatgrass, whereas in the nongrazed exclosures, forbs were dominant and appeared to have increased at the expense of western wheatgrass. The observed increase of soil C and N in the surface soil where roots dominate indicates a greater opportunity for nutrient availability and cycling, and hence enhanced grazing quality.
  • 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.