• Authors:
    • Harapiak, J.
    • Lafond, G.
    • Johnston, A.
    • Head, W.
  • Source: Journal of Production Agriculture
  • Volume: 10
  • Issue: 3
  • Year: 1997
  • Summary: A research study was conducted in Saskatchewan and Alberta to determine the potential for precision side band application of partially liquified anhydrous ammonia (AA) at sowing. While AA reduced plant stand over that observed with urea for both wheat and canola [rape], no effect on grain yields of wheat were observed from seven field trials. The use of AA did not adversely affect the rate of wheat establishment as measured by main stem Haun stage or plant development as measured by number of root axes and frequency of tillers produced. With canola, a reduction in seed yield was observed at only one of the five trial sites. The lower canola yield reflects the N loss when AA is applied on clay soils. Loss of AA on clay and silty clay soils, which were wet at application, resulted in reduced crop N uptake and lowered N use efficiency relative to urea at one wheat and two of the canola trial locations. It is suggested that given adequate seed-fertilizer separation, partially liquified AA can be safely applied at sowing in a precision side band application. Soil conditions that are known to cause N loss on application of AA, in particular wet clay and silty clay soils, may benefit more from an alternative N source such as granular urea or solution N.
  • Authors:
    • Maddux, L. D.
    • Gordon, W. B.
    • Rice, C. W.
    • Omay, A. B.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL Pages:
  • Volume: 61
  • Issue: 6
  • Year: 1997
  • Summary: With renewed interest in maintaining our soil resources, it is important to establish criteria that can describe and quantify the effect of different crop management practices on soil organic matter (SOM). We conducted this study to assess changes in SOM and other soil properties after long-term (>10 yr) continuous corn (Zea mays L.; CC) and corn-soybean rotation [Glycine max (L.) Merr,; C/SB] with and without fertilizer, Soil samples were collected from two furrow-irrigated CC and C/SB rotations on a Crete silt loam (ene, montmorillonitic, mesic Pachic Argiustoll) and a Eudora loam (coarse-silty, mixed, mesic Fluventic Hapludoll). Long term (350-d) laboratory incubation at optimum moisture and temperature conditions measured potentially mineralizable C (PMC) and N (PMN) as a measure of the active fraction of soil organic C and N, Microbial biomass C (MBC) and N (MBN), organic C and N, pH, and texture also were determined, Crop rotations that included high-residue-producing crops such as corn and addition of fertilizer increased soil organic C and N, Crop rotation did not affect PMC in the Crete soil, but addition of fertilizer significantly increased PMC by 32%. The PMN in both soils was not affected by crop rotation or fertilizer addition, Inclusion of soybean in the rotation decreased the stable and active fractions of organic C and N, Changes in soil organic C and N in response to crop rotation and fertilizer addition were related to the estimated amount of crop residues returned to the soil and to soil texture.
  • 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:
    • Kitchen, N. R.
    • Westfall, D. G.
    • Peterson, G. A.
    • Kolberg, R. L.
  • Source: Journal of Production Agriculture
  • Volume: 9
  • Issue: 4
  • Year: 1996
  • Summary: Crop N needs are not usually predicted based on cropping intensity or on tillage practice. However, N fertilizer requirements may increase dramatically as less fallow and less tillage are used in semi-arid regions of the Great Plains where summer fallow cropping is common. This long-term experiment was conducted to study the influence of N fertilizer rate, source/placement/timing (NSP), and crop rotation factors on the production of winter wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum (Sorghum bicolor L.), as well as their fertilizer N use efficiency (FNUE) for the initial years of conversion to no-till dryland farming. Research was conducted from 1987 through 1992 on two soils (Keith clay loam, a fine-silty, mixed, mesic Aridic Argiustoll and Weld loam, a fine-silty, mixed, mesic, Aridic Argiustoll) in eastern Colorado. Rotations included winter wheat-fallow (WF) and winter wheat-corn or grain sorghum-fallow (WCF). Wheat yields were similar between WF and WCF with adequate N application. Response to N fertilizer at lower rates was greater in WCF than WF because of its greater depletion of soil N. Corn production averaged 72 bu/acre with adequate N and required 1 lb/acre of N uptake to produce 1 bu/acre of grain. Current N fertilizer recommendations for wheat and corn were not adequate to insure maximum production under no-till management. Fertilizer placement significantly affected average annual rotational yield (40 to 70 lb/acre per yr difference) but application rate was more important economically. Grain biomass produced in each rotation per pound of total plant N uptake (GNUE) was 17 lb/acre per yr in WF compared with 29 lb/acre per yr for WCF. This 70% increase in average annual grain production of WCF over WF was accomplished with a 44% annual increase in fertilizer N application.
  • 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.
  • Authors:
    • Barra, J. D. E.
    • Carretera, A. R. H.
    • Oleschko, K.
  • Source: Soil & Tillage Research
  • Volume: 37
  • Issue: 1
  • Year: 1996
  • Summary: Little is known about the crop influence and the long-term effects of tillage systems on physical and morphological properties of Vertisols in the high plateau of the intertropical zone of Mexico. The purpose of the present study was to evaluate the impact of crop rotation on the development of structure and pedofeatures of Eutric Vertisols of Guanajuato, Mexico. Disturbed and undisturbed samples from the top soil (0-20 cm) of five agroecosystems differing in crop rotation (semipermanent alfalfa, two cereal crops per year, one vegetable and one cereal crop per year, three vegetable crops per year, and dryland maize) were collected. A second no-till soil sample was obtained from a nearby site under secondary vegetation and used as reference soil. Continuous and intensive cultivation lead to a significant reduction in Vertisol organic matter and total nitrogen contents. Tillage and crop rotations affected air-dried aggregate bulk densities, soil microstructure and development of pedofeatures. Calcite crystalline pedofeatures seemed to be more directly affected by the management systems used. Nodules, the most common crystalline pedofeatures in top soil of all cultivated Vertisols, were absent in no-till soils.
  • Authors:
    • Vallis, I.
    • McEwan, C. W.
    • Weier, K. L.
    • Catchpoole,V. R.
    • Myers, R. J.
  • Source: Australian Journal of Agricultural Research
  • Volume: 47
  • Issue: 1
  • Year: 1996
  • Summary: Nitrogen (N) fertilizer is being lost from sugarcane soils following application to the crop. This study was conducted to estimate the quantity of N being lost from the soil through biological denitrification and to determine the proportion of gaseous N being emitted either as N2O or as N-2. Field studies were conducted on four different soils (humic gley, alluvial massive earth, red earth and gleyed podzolic), and on different crop management systems, by installing plastic (PVC) cylinders (23.5 cm diam., 25 cm long) in the soil to a depth of 20 cm beside the plant row in a ratoon sugarcane crop. N-15-labelled KNO3 was applied as a band across each cylinder to a depth of 2.5 cm at a rate of 160 kg N/ha. After rainfall or irrigation, the cylinders were capped for 3 h intervals and gas in the headspace sampled in the morning and afternoon, for up to 4 days. Denitrification losses from the humic gley ranged from 247 g N/ha . day for cultivated plots to 1673 g N/ha . day for no-till plots. Over the sampling period, this was equivalent to 3.2% and 19.7% of the N applied, respectively. Nitrous oxide accounted for 46% to 78% of the total N lost. For the alluvial, massive earth and the red earth and gleyed podzolic, losses over the sampling period ranged from 25 to 117 g N/h . day and represented less than or equal to 1% of the N applied. Recovery of N-15 in the soil ranged from 67% at the first sampling on the red earth soil to 4.9% at the third sampling on the alluvial, massive earth soil. In a glasshouse study, intact soil cores (23.5 cm diam., 20 cm long), taken from the humic gley and the alluvial, massive earth, were waterlogged after band application of N-15-labelled KNO3 at a rate of 160 kg N/ha. Gas samples from the headspace were taken after 3 h, and then morning and afternoon for the next 14 days. Denitrification losses ranged from 13.2 to 38.6% of N applied with the majority of gaseous N loss occurring as N-2. Total N-15 recoveries after 14 days, including the evolved gases, ranged from 68.7 to 88.2%. We conclude that denitrification is a major cause of fertilizer N loss from fine-textured soils, with nitrous oxide the major gaseous N product when soil nitrate concentrations are high.
  • Authors:
    • Sinclair, T. R.
    • Amir, J.
  • Source: Field Crops Research
  • Volume: 47
  • Issue: 1
  • Year: 1996
  • Summary: Cereal Cyst Nematode (CCN, Heterodera avenae Woll.) has been shown to be a devastating pest for wheat (Triticum aestivum L.) in dryland regions. Following in the season preceding the cropping season has been hypothesized to sanitize the soil of CCN and allow wheat production. This paper explores management options that might allow the continuous production of wheat in these regions. In a 20-year study in the Negev, Israel, on a sandy loam, loessial, soil, it was found that in those seasons with high rainfall there was virtually no decrease in annual wheat yields for continuous crops as compared to biennial fallow yields obtained with the conventional wheat system. The hypothesis that high soil water content substantially alleviates the damage resulting from CCN infestation was confirmed in a pot study. A practical solution for maintaining high soil water content in the field was to leave a straw mulch on the soil surface to decrease soil evaporation. A chopper was added to a grain harvester to finely chop the straw so that it settles to the soil surface through the stubble, and a no-till drill was used for sowing through the straw. The straw-mulch system was shown to result in annual yields from continuous wheat that were equivalent to yields in alternate years with the conventional fallow wheat system, thereby doubling wheat production in this dryland region.
  • Authors:
    • Franzluebbers, A. J.
    • Arshad, M. A.
  • Source: Soil Science Society of America Journal
  • Volume: 60
  • Issue: 5
  • Year: 1996
  • Summary: Changes in soil organic matter (SOM) pools during adoption of reduced (RT) or zero tillage (ZT) can influence soil physical properties, nutrient cycling, and CO2 flux between soil and atmosphere. We determined soil organic C (SOC), soil microbial biomass C (SMBC), basal soil respiration (BSR), and mineralizable N to a depth of 200 mm at the end of 3, 5, and 6 yr after implementation of tillage management on a Falher clay (fine, montmorillonitic, frigid Typic Natriboralf) near Rycroft, Alberta, in a canola (Brassica campestris L.)-wheat (Triticum Aestivum L.)-barley (Hordeum vulgare L.)-fallow cropping system. At the end of 6 yr, SOC was not different among tillage regimes and averaged 8.6 kg m−2. At the end of 3 and 5 yr, SMBC was not significantly different among tillage regimes, but at the end of 6 yr SMBC was 7% greater in RT and 9% greater in ZT than in conventional tillage (CT). Basal soil respiration and mineralizable N at the end of 6 yr were not different among tillage regimes following barley and averaged 2.7 g CO2-C m−2 d−1 and 5.0 g inorganic N m−2 24 d−1, respectively. However, BSR following fallow was 2.2, 2.5, and 2.6 g CO2-C m−2 d−1 in CT, RT, and ZT, respectively. Mineralizable N following fallow was 5.8 g inorganic N m−2 (24 d)−1 in RT and ZT and 7.3 g inorganic N m−2 (24 d)−1 in CT. At 0 to 50 mm, there was no significant increase in SOC at the end of 6 yr, a 17 to 36% increase in SMBC, and a 12 to 69% increase in BSR with ZT compared with CT, depending on rotation phase. Relatively small changes in SOM pools with adoption of conservation tillage may be attributable to the large amount of SOM initially present and the cold, semiarid climate that limits SOM turnover.
  • 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.