• Authors:
    • Nielsen, D. C.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 3
  • Year: 2011
  • Summary: Forages could be used to diversify reduced and no-till dryland cropping systems from the traditional wheat ( Triticum aestivum L.)-fallow system in the semiarid central Great Plains. Forages present an attractive alternative to grain and seed crops because of greater water use efficiency and less susceptibility to potentially devastating yield reductions due to severe water stress during critical growth stages. However, farmers need a simple tool to evaluate forage productivity under widely varying precipitation conditions. The objectives of this study were to (1) quantify the relationship between crop water use and dry matter (DM) yield for soybean ( Glycine max L. Merrill), (2) evaluate changes in forage quality that occur as harvest date is delayed, and (3) determine the range and distribution of expected DM yields in the central Great Plains based on historical precipitation records. Forage soybean was grown under a line-source gradient irrigation system to impose a range of water availability conditions at Akron, CO. Dry matter production was linearly correlated with water use resulting in a production function slope of 21.2 kg ha -1 mm -1. The slope was much lower than previously reported for forage production functions for triticale ( X Triticosecale Wittmack) and millet ( Setaria italic L. Beauv.), and only slightly lower than slopes previously reported for corn ( Zea mays L.) and pea ( Pisum sativa L.) forage. Forage quality was relatively stable during the last four weeks of growth, with small declines in crude protein (CP) concentration. Values of CP concentration and relative feed value indicated that forage soybean was of sufficient quality to be used for dairy feed. A standard seed variety of maturity group VII was found to be similar (in both productivity and quality) to a variety designated as a forage type. The probability of obtaining a break-even yield of at least 4256 kg ha -1 was 90% as determined from long-term precipitation records used with the production function. The average estimated DM yield was 5890 kg ha -1 and ranged from 2437 to 9432 kg ha -1. Regional estimates of mean forage soybean DM yield ranged from 4770 kg ha -1 at Fort Morgan, CO to 6911 kg ha -1 at Colby, KS. Forage soybean should be considered a viable alternative crop for dryland cropping systems in the central Great Plains.
  • Authors:
    • Benjamin, J. G.
    • Nielsen, D. C.
    • Vigil, M. F.
  • Source: Field Crops Research
  • Volume: 120
  • Issue: 2
  • Year: 2011
  • Summary: No-till dryland winter wheat ( Triticum aestivum L.)-fallow systems in the central Great Plains have more water available for crop production than the traditional conventionally tilled winter wheat-fallow systems because of greater precipitation storage efficiency. That additional water is used most efficiently when a crop is present to transpire the water, and crop yields respond positively to increases in available soil water. The objective of this study was to evaluate yield, water use efficiency (WUE), precipitation use efficiency (PUE), and net returns of cropping systems where crop choice was based on established crop responses to water use while incorporating a grass/broadleaf rotation. Available soil water at planting was measured at several decision points each year and combined with three levels of expected growing season precipitation (70, 100, 130% of average) to provide input data for water use/yield production functions for seven grain crops and three forage crops. The predicted yields from those production functions were compared against established yield thresholds for each crop, and crops were retained for further consideration if the threshold yield was exceeded. Crop choice was then narrowed by following a rule which rotated summer crops (crops planted in the spring with most of their growth occurring during summer months) with winter crops (crops planted in the fall with most of their growth occurring during the next spring) and also rotating grasses with broadleaf crops. Yields, WUE, PUE, value-basis precipitation use efficiency ($PUE), gross receipts, and net returns from the four opportunity cropping (OC) selection schemes were compared with the same quantities from four set rotations [wheat-fallow (conventional till), (WF (CT)); wheat-fallow (no-till), (WF (NT)); wheat-corn ( Zea mays L.)-fallow (no-till), (WCF); wheat-millet ( Panicum miliaceum L.) (no-till), (WM)]. Water use efficiency was greater for three of the OC selection schemes than for any of the four set rotations. Precipitation was used more efficiently using two of the OC selection schemes than using any of the four set rotations. Of the four OC cropping decision methods, net returns were greatest for the method that assumed average growing season precipitation and allowed selection from all possible crop choices. The net returns from this system were not different from net returns from WF (CT) and WF (NT). Cropping frequency can be effectively increased in dryland cropping systems by use of crop selection rules based on water use/yield production functions, measured available soil water, and expected precipitation.
  • Authors:
    • Nord, E. A.
    • Curran, W. S.
    • Mortensen, D. A.
    • Mirsky, S. B.
    • Jones, B. P.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: Rolled cover crop mulches can suppress weeds in subsequent cash crops, reduce the need for herbicides, and allow organic no-till cash crop establishment. This study investigated the weed suppressiveness of a cereal rye ( Secale cereale L.) cover crop mulch across varying weed seedbank density. Cereal rye was seeded at two dates in the fall and terminated at five dates in the spring to create biomass ranging from 100 to 1600 g m -2. The first three termination dates included both herbicide (glyphosate) and rolling of the rye, while later three dates were only rolled. Soybean [ Glycine max (L.) Merr.] was no-till planted after rye termination, and weed biomass and soybean yield were assessed. Spring termination date more strongly affected cereal rye biomass than fall planting date; a termination delay of 5 to 15 d compensated for a planting delay of 30 d. Weed biomass generally declined with increasing cereal rye biomass, and this relationship was stronger at higher weed seedbank densities. Supplemental weed control reduced weed biomass compared to no supplemental control and postherbicide was more effective than cultivation. While increasing cereal rye biomass was associated with a decline in soybean yield in 2009, it did not consistently impact soybean stand. Instead soybean stand establishment appeared to be impacted by high cover crop biomass and changing edaphic conditions at planting. Future research should focus on improved technology for direct seeding in high residue environments and developing longer term cropping systems less reliant on tillage and herbicides.
  • Authors:
    • Smith, D. R.
    • Gal, A.
    • Vyn, T. J.
    • Omonode, R. A.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 1
  • Year: 2011
  • Summary: Few experiments have directly compared the long-term effects of moldboard, chisel, and no-till tillage practices on N 2O emissions from the predominant crop rotation systems in the midwestern United States. This study was conducted from 2004 to 2006 on a tillage and rotation experiment initiated in 1975 on a Chalmers silty clay loam (a Typic Endoaquoll) in west-central Indiana. Our objectives were to assess (i) long-term tillage (chisel [CP], moldboard plow [MP], and no-till [NT]), rotation (continuous corn [ Zea mays L.] and corn-soybean [ Glycine max (L.) Merr.]), and rotation * tillage interaction effects on soil N 2O emission, and (ii) how soil N 2O emission is related to environmental factors during corn production under identical N fertilizer management. Seasonal N 2O emissions were measured at intervals ranging from a few days to biweekly for up to 14 sampling dates in each growing season for corn. Nitrous oxide emissions during the growing season were significantly affected by tillage and rotation but not their interaction; however, 50% of total emissions occurred shortly after N application regardless of tillage or rotation practices. Seasonal cumulative emissions were significantly lower under NT but not statistically different for CP and MP. Overall, emissions under NT were about 40% lower relative to MP and 57% lower relative to CP. Rotation corn lowered N 2O emissions by 20% relative to continuous corn. Higher N 2O emission under MP and CP appeared to be driven by soil organic C decomposition associated with higher levels of soil-residue mixing and higher soil temperatures.
  • Authors:
    • Forgey, D.
    • Beck, D.
    • Osborne, S. L.
    • Dagel, K. J.
  • Source: Agricultural Journal
  • Volume: 6
  • Issue: 2
  • Year: 2011
  • Summary: Incorporating cover crops into current production systems can have many beneficial impacts on the current cropping system including decreasing erosion, improving water infiltration, increasing soil organic matter and biological activity but in water limited areas caution should be utilized. A field study was established in the fall of 2007 to evaluate the impact of incorporating cover crops into a no-till crop production system in Central South Dakota. Cover crops utilized in the experiment were: cowpea ( Vigna sinensis), lentils ( Lens culinaris), canola ( Brassica napus), cow/can/len, cow/can, can/len, radish ( Raphanus sativus)/cow/can/len and turnip ( Brassica napa)/cow/len/can combos all compared to no-cover crop. Cover crops were allowed to grow throughout the fall and winter killed. Cover crop biomass was collect prior to a killing frost. The following spring corn was planted and in-season growth and grain yield was evaluated. When cover crops were incorporated into the production practices there was a significant increase in grain yield compared to the no cover crop treatment without additional nitrogen. While when nitrogen was applied to the corn crop yields did not increase as dramatically compared to the no cover crop treatment. Fall cover crops had the ability to scavenge residual soil nitrate and make it plant available for the following crop providing a positive environmental benefit beyond the above mentioned benefits.
  • Authors:
    • Parr, M.
    • Grossman, J. M.
    • Reberg-Horton, S. C.
    • Brinton, C.
    • Crozier, C.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 6
  • Year: 2011
  • Summary: Sixteen winter annual cover crop cultivars were grown in North Carolina to determine total N accumulation, biological N fixation (BNF) potential, and compatibility with a roller-crimper-terminated organic corn ( Zea mays L.) production system. Cover crops and termination dates were tested in a stripped block design. Treatments included hairy vetch ( Vicia villosa Roth), common vetch ( Vicia sativa L.), crimson clover ( Trifolium incarnatum L.), Austrian winter pea ( Pisum sativum L.), berseem clover ( Trifolium alexandrinum L.), subterranean clover ( Trifolium subterraneum L.), narrow leaf lupin ( Lupinus angustifolius L.), and Balansa clover ( Trifolium michelianum Savi.), as well as bicultures of rye ( Secale cereale L.), hairy vetch, and Austrian winter pea. Roller-crimper termination occurred in mid-April, early May, and mid-May. Total biomass, N concentration, and C/N ratios were determined for cover crops at all roll times and natural 15N abundance at the optimal kill date. Hairy vetch and crimson clover monocultures had the greatest overall biomass in 2009, and bicultures the greatest biomass in 2010. Crimson clover successfully terminated in late April, hairy vetch and Austrian winter pea in mid-May, and berseem clover and common vetch in late May. All cover crops except lupin and subterranean clover derived between 70 and 100% of their N from the atmosphere. Corn response to cover crop mulches was significantly affected by the time of rolling, with poor stands resulting from competition with insufficiently terminated mulches. Crimson, Balansa, and subterranean clover mulches resulted in poor corn yields despite relatively high levels of total N. The highest corn yields were achieved in hairy vetch and rye plus hairy vetch bicultures.
  • Authors:
    • Paudel, B. R.
    • Anderson, S. H.
    • Udawatta, R. P.
  • Source: Applied Soil Ecology
  • Volume: 48
  • Issue: 2
  • Year: 2011
  • Summary: Establishment of buffers and incorporation of trees and shrubs are believed to improve soil quality and thereby improve water quality from grazed pasture systems. Although enzyme activities and water stable aggregates have been identified as measurable soil quality parameters for early responses to changes in soil management, the literature lacks information on those parameters for grazing systems with agroforestry buffers. The objective of this study was to examine the activities of fluorescein diacetate (FDA) hydrolase, dehydrogenase, beta-glucosidase and beta-glucosaminidase, the percentage of water stable aggregates (WSA) and soil organic carbon and nitrogen as soil quality parameters for grazed pasture and row-crop systems. The study consisted of four management treatments: grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row-crop (RC). The WSA was determined by wet sieving method while the enzyme activities were colorimetrically quantified using a spectrophotometer in laboratory assays. Soil organic carbon (SOC) and total nitrogen (TN) contents were also determined. Two soil depths (0-10 and 10-20 cm) were analyzed for all treatments. The row-crop treatment showed significantly lower activities compared to all other treatments for beta-glucosidase and beta-glucosaminidase enzymes along with lower WSA. The dehydrogenase activities were significantly higher in GP treatment compared to RC treatment. The FDA hydrolase activities were not significantly different among treatments. Surface soil revealed higher enzyme activities and higher WSA than the sub-surface soil. The treatment by depth interaction was significant for beta-glucosidase and beta-glucosaminidase enzymes. The soil organic carbon and total nitrogen data strongly supported the results of enzyme activities and WSA. Implications can be made that perennial vegetation enhances organic matter accumulation in the soil, has minimum disturbance to the soil and will have positive impacts on the ecosystem.
  • Authors:
    • Rao, S. C.
    • Northup, B. K.
  • Source: Crop Science
  • Volume: 51
  • Issue: 4
  • Year: 2011
  • Summary: Sources and methods of use of organic nitrogen (N) in the southern Great Plains (SGP) need testing to find alternatives to increasingly expensive inorganic fertilizer. We examined the function of grass pea ( Lathyrus sativus L.), a cool-season pulse, as a preplant N source for continuous, no-till winter wheat ( Triticum aestivum L.). The study was conducted in central Oklahoma (35degrees40′N, 98degrees00′W, elevation 414 masl) from 2004 to 2008, on three replicate blocks of four experimental plots (6 by 10 m). Inoculated grass pea seed ('AC-Greenfix') was sown during late summer fallow (mid-August) in one randomly chosen plot per block (75 kg ha -1, 60-cm rows; 75% germination). Three additional plots per block mimicked summer fallow with 0 (control), 40, or 80 kg N ha -1 inorganic fertilizer applied. All treatments were repeated on the same plots throughout the study. Samples were collected from grass pea plots at flowering in early October to define aboveground biomass and analyzed for N concentration and digestibility. Aboveground biomass of grass pea was shredded with a flail mower and left on the soil surface, fertilizer treatments were applied, and wheat ('Jagger') was sown (100 kg ha -1, 20-cm rows). Aboveground wheat biomass was collected at three growth stages (elongation, flowering, physiological maturity) and analyzed for N concentration. Grass pea aboveground biomass contained enough N to meet the needs of wheat at planting in only 1 yr. Wheat biomass and amounts of N in wheat aboveground biomass in response to grass pea were intermediate between the 0 and 40 kg applied N ha -1, as was yield and N accumulated in wheat grain. Therefore, grass pea was not effective as a preplant source of N for continuous no-till winter wheat in the SGP. Additional research is required to define factors that limit the function of grass pea as a source of N for continuous no-till winter wheat and its potential function in other crop rotations.
  • Authors:
    • Jabro, J. D.
    • Lartey, R. T.
    • Evans, R. G.
    • Allen, B. L.
    • Sainju, U. M.
    • Lenssen, A. W.
    • Caesar-TonThat, T.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: Novel management practices are needed to increase dryland soil organic matter and crop yields that have been declining due to long-term conventional tillage with spring wheat ( Triticum aestivum L.)-fallow system in the northern Great Plains, USA. The effects of tillage, crop rotation, and cultural practice were evaluated on dryland crop biomass (stems+leaves) yield, surface residue, and soil organic C (SOC) and total N (STN) at the 0-20 cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) from 2004 to 2007 in eastern Montana, USA. Treatments were two tillage practices [no-tillage (NT) and conventional tillage (CT)], four crop rotations [continuous spring wheat (CW), spring wheat-pea ( Pisum sativum L.) (W-P), spring wheat-barley ( Hordeum vulgaris L.) hay-pea (W-B-P), and spring wheat-barley hay-corn ( Zea mays L.)-pea (W-B-C-P)], and two cultural practices [regular (conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height) and ecological (variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height)]. Crop biomass and N content were 4 to 44% greater in W-B-C-P than in CW in 2004 and 2005 and greater in ecological than in regular cultural practice in CT. Soil surface residue amount and C and N contents were greater in NT than in CT, greater in CW, W-P, and W-B-C-P than in W-B-P, and greater in 2006 and 2007 than in 2004 and 2005. The SOC and STN concentrations at 0-5 cm were 4 to 6% greater in CW than in W-P or W-B-P in NT and CT from 2005 and 2007. In 2007, SOC content at 10-20 cm was greater in W-P and W-B-P than in W-B-C-P in CT but STN was greater in W-B-P and W-B-C-P than in CW in NT. From 2004 to 2007, SOC and STN concentrations varied at 0-5 cm but increased at 5-20 cm. Diversified crop rotation and delayed planting with higher seed rates and banded N fertilization increased the amount of crop biomass returned to the soil and surface residue C and N. Although no-tillage increased surface residue C and N, continuous nonlegume cropping increased soil C and N levels at the surface layer compared with other crop rotations. Continued return of crop residue from 2004 to 2007 may increase soil C and N levels but long-term studies are needed to better evaluate the effect of management practices on soil C and N levels under dryland cropping systems in the northern Great Plains.
  • Authors:
    • Jones, B. P.
    • Sequeira, C. H.
    • Alley, M. M.
  • Source: Soil Biology and Biochemistry
  • Volume: 43
  • Issue: 2
  • Year: 2011
  • Summary: Particulate organic matter (POM) and light fraction (LF) organic matter are potentially labile (active) fractions of soil organic matter (SOM) that have been shown to be indicators of short-term changes in soil management practices (e.g. tillage, manure and fertilizer applications, and crop rotation). These two fractions consist mainly of partially decomposed plant residues, microbial residues, seeds, and spores forming organo-mineral complexes with soil mineral particles; however, they cannot be used as synonyms because of their different chemical composition and structure. Particulate-OM is recovered by size-based procedures while LF is generally recovered in two distinct fractions [free-LF (FLF) and occluded-LF (OLF)] using density-based solutions in conjunction with soil-aggregate disruption. Solutions used in these density-based separations have most commonly varied in density from 1.6 to 2.0 g cm -3. Sodium iodide (NaI) and sodium polytungstate (SPT) are the chemicals most often used to prepare the density solutions in LF recovery but comparisons of the effectiveness of two solutions have not been conducted. The objectives of this research were: (1) compare the efficiency of similar density solutions of NaI and SPT in recovering FLF; and (2) compare POM, FLF, and OLF as possible sensitive indices of short-term soil changes due to tillage management. Soil samples were collected at 0-15 cm depth from a cropping system experiment conducted on a silt loam Ultisol. Plots selected for sampling had received either reduced till (RT) or no-till (NT), and cropping was continuous corn silage for a period of 3 years prior to sampling. Solutions of NaI and SPT at densities of 1.6 and 1.8 g cm -3 were used to recover FLF, and OLF was recovered with SPT solution at a density of 2.0 g cm -3 from the soil pellet remaining after FLF recovery with SPT 1.6 g cm -3. The average total soil organic carbon (SOC) content of these samples was of 12.7 g kg -1, and carbon-POM (C-POM), carbon-FLF (C-FLF), and carbon-OLF (C-OLF) represented 22.4, 5.5, and 5.2% of it, respectively. In general, C-FLF and nitrogen-FLF (N-FLF) contents recovered did not differ significantly between chemical solutions (NaI or SPT) adjusted to the same density (1.6 or 1.8 g cm -3). Increasing the density within a specific solution (NaI or SPT) resulted in significantly higher C-FLF and N-FLF recovery. For instance, C-FLF recovery averaged 637 and 954 mg kg -1 at 1.6 and 1.8 g cm -3, respectively. For both chemicals increasing density from 1.6 to 1.8 g cm -3 reduced the variability in recovering C-FLF and N-FLF with coefficient of variation values decreasing from a range of 14.9-19.1% for densities of 1.6 g cm -3 to 6.7-10.4% when densities increased to 1.8 g cm -3. In the present work, POM and OLF were more sensitive than FLF to changes in tillage management, with significantly greater amounts of the sensitive fractions in RT samples. A better sensitivity of FLF would be expected if treatments dealing with residue input (e.g. crop rotation and cover crop) were evaluated.