• Authors:
    • Schillinger, W.
    • Wuest, S.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Farmers in the low-precipitation (<300 mm annual) region of the Inland Pacific Northwest of the USA practice summer fallow to produce winter wheat ( Triticum aestivum L.) in a 2-yr rotation. No-till fallow (NTF) is ideal for wind erosion control but is not widely practiced because of seed-zone soil drying during the summer, whereas adequate seed-zone water for germination and emergence of deep-sown winter wheat can generally be retained with tilled fallow (TF). Successful establishment of winter wheat from late August- early September planting is critical for optimum grain yield potential. A 6-yr field study was conducted to determine if accumulations of surface residue under long-term NTF might eventually be enough to substitute for TF in conserving seed-zone water over summer. Averaged over the 6 yr, residue rates of 1500, 6000, and 10 500 kg ha -1 (1*, 4*, and 7* rates, respectively) on NTF produced incrementally greater seed-zone water but were not capable of conserving as much as TF. Total root zone (0-180 cm) over-summer water loss was greatest in the 1 * NTF whereas there were no significant differences in the 4* and 7* NTF versus TF. Average precipitation storage efficiency ranged from 33% for 1* NTF to 40% for TF. We conclude that for the low-precipitation winter wheat-summer fallow region of the Inland Pacific Northwest: (i) Cumulative water loss during the summer from NTF generally exceeds that of TF; (ii) there is more extensive and deeper over-summer drying of the seed-zone layer with NTF than with TF; (iii) increased quantities of surface residue in NTF slow the rate of evaporative loss from late-summer rains, and (iv) large quantities of surface residue from April through August will marginally enhance total-profile and seed-zone water in NTF, but will not retain adequate seed-zone water for early establishment of winter wheat except sometimes during years of exceptionally high precipitation or when substantial rain occurs in mid-to-late August.
  • Authors:
    • Laboski, C.
    • Andraski, T.
    • Yague, M.
  • Source: Journal of Environmental Quality
  • Volume: 40
  • Issue: 6
  • Year: 2011
  • Summary: Greater demand for corn ( Zea mays L.) stover for bioenergy use may lead to increased corn production acreage with minimal surface residue cover, resulting in greater risk for soil erosion and phosphorus (P) losses in runoff. A rainfall simulation study was conducted to determine the effects of spring-applied dairy cow ( Bos taurus) manure (none, in-barn composted, and exterior walled-enclosure pit) with >200 g kg -1 organic solids content following fall corn biomass removal with and without incorporation (chisel plow [CP] and no-till [NT]) on sediment and P in runoff. Runoff was collected from a 0.83-m 2 area for 60 min following the onset of rainfall simulation (76 mm h -1), once in spring and once in fall. Runoff dissolved reactive P (DRP) and dissolved organic P (DOP) concentrations were positively correlated with manure P rate and were higher in NT compared with CP. Conversely, sediment and particulate P (PP) concentrations in runoff were inversely correlated with manure P rate (and manure solids) and were higher in CP compared with NT. Runoff volume where no manure was applied was higher in NT than in CP in spring but similar in fall. The addition of manure reduced runoff volumes by an average of 82% in NT and 42% in CP over spring and fall. Results from this study indicate that surface application of dairy manure with relatively high solids content may reduce sediment and PP losses in runoff without increasing the risk of increased DRP and DOP losses in the year of application where corn biomass is harvested.
  • Authors:
    • Li, Z.
    • Liu, W. Z.
    • Zhang, X. C.
    • Chen, J.
  • Source: Agricultural and Forest Meteorology
  • Volume: 151
  • Issue: 10
  • Year: 2011
  • Summary: Trends and uncertainty of the climate change impacts on hydrology, soil erosion, and wheat production during 2010-2039 at El Reno in central Oklahoma, USA, were evaluated for 12 climate change scenarios projected by four GCMs (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emissions scenarios (A2, B2, and GGa). Compared with the present climate, overall t-tests ( n=12) show that it is almost certain that mean precipitation will decline by some 6% (>98.5% probability), daily precipitation variance increase by 12% (>99%), and maximum and minimum temperature increase by 1.46 and 1.26 degrees C (>99%), respectively. Compared with the present climate under the same tillage systems, it is very likely (>90%) that evapotranpiration and long-term soil water storage will decease, but runoff and soil loss will increase despite the projected declines in precipitation. There will be no significant changes in wheat grain yield. Paired t-tests show that daily precipitation variance projected under GGa is greater than those under A2 and B2 ( P=0.1), resulting in greater runoff and soil loss under GGa ( P=0.1). HadCM3 projected greater mean annual precipitation than CGCM2 and CSIRO ( P=0.1). Consequently, greater runoff, grain yield, transpiration, soil evaporation, and soil water storage were simulated for HadCM3 ( P=0.1). The inconsistency among GCMs and differential impact responses between emission scenarios underscore the necessity of using multi-GCMs and multi-emission scenarios for impact assessments. Overall results show that no-till and conservation tillage systems will need to be adopted for better soil and water conservation and environmental protection in the region during the next several decades.
  • Authors:
    • Gibson, L. R.
    • Singer, J. W.
    • Blaser, B. C.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 4
  • Year: 2011
  • Summary: Interseeding red clover ( Trifolium pratense L.) or alfalfa ( Medicago sativa L.) into winter cereals in the North Central United States can provide forage and a green manure crop. We hypothesized that winter cereal canopy traits such as leaf area index (LAI) and whole plant dry matter (DM) would influence interseeded legume establishment and productivity, yet the effect of canopy traits on resource competition in intercropping systems is not well understood. This study was conducted from 2005 to 2007 to evaluate the impact of diverse cereal canopy traits on the establishment of frost-seeded legume intercrops. In March, red clover and alfalfa were frost-seeded into three winter wheat ( Triticum aestivum L.) and three triticale (X Triticosecale Wittmack) varieties selected for differences in maximum LAI, plant height, and DM. Across three growing seasons, the cereals produced a range of LAI from 2.1 to 6.2 and whole plant harvest DM of 817 to 2029 g m -2. In the 2 yr with legume data, densities were influenced by cereal 1 yr and DM was affected by cereal both years. Alfalfa and red clover densities were similar, yet DM production was 42% higher in red clover 40 d after grain harvest. The presence of a legume intercrop did not affect grain yield, but reduced weed densities and weed DM 40 d after harvest. Producers implementing this intercrop may select cereal varieties based on grain yield, but must be cautious of varieties known to produce above normal LAI values because of the potential to reduce legume productivity.
  • Authors:
    • Brennan, E. B.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: Winter cover crops can add soil organic matter, improve nutrient cycling, and suppress weeds in organic vegetable systems. A 2-yr study was conducted on organic farms in Salinas and Hollister, CA, to evaluate the effect of seeding rate (SR) and planting arrangement on cover crop density, ground cover, and cover crop and weed dry matter (DM) with a mixed cover crop. The mix contained legumes (35% Vicia faba L., bell bean; 15% Vicia dasycarpa Ten., woolypod vetch; 15% Vicia benghalensis L., purple vetch; and 25% Pisum sativum L., pea) and 10% oat (Avena sativa L.) by seed weight. Three SRs (112, 224, and 336 kg ha(-1)) and two planting arrangements (one-way versus grid pattern) were evaluated. Planting arrangement had no effect on the variables measured. When weeds were abundant, weed DM declined linearly with increasing SR from approximately 300 kg ha(-1) at the low SR to <100 kg ha(-1) at the high SR. Increasing SR increased oat and legume DM early in the season, but did not affect final cover crop DM that ranged from 7 to 12 Mg ha(-1). Year affected final cover crop DM production at both sites. The legume DM portion of the total cover crop declined through the season but varied between sites and year, probably due to soil and climatic differences. Higher SRs may be cost effective because weed control is expensive and cover crop seed is a relatively small component of cover cropping costs in this region.
  • Authors:
    • Carson, M.
  • Source: Plant Disease
  • Volume: 95
  • Issue: 12
  • Year: 2011
  • Summary: The use of race-specific seedling genes for resistance is the primary means of controlling crown rust of oat ( Puccinia coronata f. sp. avenae) in the United States. To better utilize those resistance genes, knowledge of the occurrence and frequency of corresponding virulence in the population of P. coronata f. sp. avenae in the United States is essential. In total, 571 single-pustule isolates of oat crown rust were collected from cultivated and wild oat ( Avena sativa and A. fatua, respectively) in the major oat production areas of the United States from 2006 through 2009. They were tested for virulence on seedlings of 31 differential oat lines in the greenhouse. In all, 201 races were found among the 357 isolates from the spring oat region of the north-central United States, and 140 races were found among 214 isolates from the southern winter oat region. The crown rust populations from the winter and spring oat regions were clearly differentiated from one another, differing in the frequency of virulence for 24 of the 31 differentials. Some virulence associations previously reported in the U.S. oat crown rust population were also found in both regions in this survey, even when the dataset was clone corrected. Associations between virulence to the Pc genes were predominately positive in both regions but both positive and negative associations occurred more frequently in the winter oat region, where sexual reproduction does not occur. Some of the virulence diversity in the oat crown rust population in the United States can be related to the deployment of resistance genes in commercial oat cultivars and virulence associations existing in the oat crown rust population. When data from a previous report covering 2001 through 2005 is combined with data reported in this article, the mean virulence of the U.S. populations of crown rust continued to increase from 2001 to 2009. Virulence to Pc38, Pc39, Pc45, Pc48, Pc52, Pc55, Pc56, Pc57, Pc59, Pc62, Pc63, Pc64, Pc68, and Pc96 significantly increased in one or both regions during this time period. No significant declines in virulence frequency were found in either region. Genes for crown rust resistance derived from A. sterilis appear to be as rapidly defeated as has happened to Pc genes from A. sativa. There is an urgent need to find additional sources of effective resistance to P. coronata f. sp. avenae and introgress it into adapted oat cultivars.
  • Authors:
    • Tomer, M.
    • Cambardella, C.
    • Singer, J.
    • Moorman, T.
    • Kovar, J.
  • Source: Journal of Environmental Quality
  • Volume: 40
  • Issue: 2
  • Year: 2011
  • Summary: Injection of liquid swine manure disturbs surface soil so that runoff from treated lands can transport sediment and nutrients to surface waters. We determined the effect of two manure application methods on P fate in a corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] production system, with and without a winter rye ( Secale cereale L.)-oat ( Avena sativa L.) cover crop. Treatments included: (i) no manure; (ii) knife injection; and (iii) low-disturbance injection, each with and without the cover crop. Simulated rainfall runoff was analyzed for dissolved reactive P (DRP) and total P (TP). Rainfall was applied 8 d after manure application (early November) and again in May after emergence of the corn crop. Manure application increased soil bioavailable P in the 20- to 30-cm layer following knife injection and in the 5- to 20-cm layer following low-disturbance injection. The low-disturbance system caused less damage to the cover crop, so that P uptake was more than threefold greater. Losses of DRP were greater in both fall and spring following low-disturbance injection; however, application method had no effect on TP loads in runoff in either season. The cover crop reduced fall TP losses from plots with manure applied by either method. In spring, DRP losses were significantly higher from plots with the recently killed cover crop, but TP losses were not affected. Low-disturbance injection of swine manure into a standing cover crop can minimize plant damage and P losses in surface runoff while providing optimum P availability to a subsequent agronomic crop.
  • Authors:
    • Leap, J.
    • Klonsky, K. M.
    • Shennan, C.
    • Smith, R. F.
    • Muramoto, J.
    • Ruiz, M. S.
    • Gliessman, S. R.
  • Source: HortScience
  • Volume: 46
  • Issue: 8
  • Year: 2011
  • Summary: Legume/cereal mixed winter cover crops are commonly used by organic growers on the central coast of California, but they are unable to provide sufficient nitrogen (N) for a high N-demanding vegetable crop such as broccoli and supplemental fertilizer application may be necessary. The goals of this project were to evaluate the contribution of N from a mixed legume/cereal cover crop (CC) and feather meal and blood meal as organic fertilizers (OF) to an organic broccoli crop and to evaluate economic benefits of CC and OF to the subsequent organic broccoli crop. Trials were conducted at two sites (A and B) with different management histories. Cover crops were grown over the winter and incorporated into the soil in the spring and subsequently broccoli [ Brassica oleracea L. (Italica group)] was grown in 2006 at both sites and in 2007 at B only. Cover crop and no CC treatments were grown with supplemental organic fertilizers at four fertility levels (0, 84, 168, and 252 kg N/ha of OF) with four replicates. Generally broccoli head yields at A (14.9 to 26.3 Mg.ha -1) were higher than at B (0.7 to 17.4 Mg.ha -1 in 2006 and 5.5 to 17.9 Mg.ha -1 in 2007). Yield and aboveground biomass N were significantly increased by OF at rates up to 168 kg N/ha at A and to 252 kg N/ha at B and by CC in 2006 at both sites but not in 2007 at B. Although N content of the CC was similarly low at A (2006) and at B (2007), immobilization of soil mineral N occurred only at B. This suggests that the addition of a low N content CC was offset by high N mineralization from the soil at A with a long organic management history (greater than 33 years). Supplemental fertilizer applications may be necessary to achieve optimal yields, but the amount needed can be reduced by cover cropping in fields with a long history of cover crop-based organic management (A) or when cover crop N content is sufficiently high to prevent immobilization (B, 2006). Soil NO 3-N patterns suggest a pre-side dress nitrate test may also be useful for N management in organic broccoli. Use of cover crops increased net return above harvest and fertility costs when the yield reduction by N immobilization did not take place. However, the net return increase by the use of cover crops tended to diminish as the rate of OF application increased.
  • Authors:
    • Burdick, B. A.
    • Massey, R. E.
    • Nelson, K. A.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 3
  • Year: 2011
  • Summary: Early-seeded soybean [ Glycine max (L.) Merr.] relay intercropped into standing wheat ( Triticum aestivum L.) using soybean seed-coat technology may allow profitable wheat production in the Midwest on highly erodible soils. Dry conditions in mid- to late June have reduced relay intercropped soybean stands and yield in some years. We hypothesized that using glyphosate as a wheat harvest aid would reduce the impact of wheat interference on relay intercropped soybean grain yield and increase gross margins. Field research conducted over four site-years in upstate Missouri evaluated timings for application of glyphosate as a harvest aid on wheat and relay intercropped soybean. The cost effectiveness of these cropping systems was compared to full-season soybean, double-cropped wheat-soybean, and wheat-only production systems. Glyphosate applied to wheat 1 wk before harvest, after late dough, in a relay intercrop production system with coated-soybean maintained wheat grain yields similar to nontreated wheat, and increased soybean grain yields 290 to 770 kg ha -1 compared to nontreated wheat relay intercropped or double-cropped with soybean. Earlier glyphosate application timings (2-3 wk before wheat harvest) reduced wheat grain yields 10 to 25% and grain density 3 to 13%, but soybean yield increased 430 to 520 kg ha -1 compared to nontreated wheat in a relay intercrop system. A relay intercrop system with seed coat technology and glyphosate as a harvest aid may allow farmers to maintain wheat in their crop rotation while minimizing risk associated with early fall frost or dry conditions at seeding that may otherwise decrease double-crop soybean yields.
  • Authors:
    • Ferguson, R.
    • Boquet, D.
    • Paxton, K.
  • Source: Louisiana Agriculture
  • Volume: 54
  • Issue: 2
  • Year: 2011
  • Summary: An experiment was conducted from 2001 to 2009 in Louisiana to analyze the profit potential of a soyabean/wheat double-crop was compared to a monocrop system. Wheat was planted in early to mid-November each year, and soybeans were planted immediately following wheat harvest, generally in mid-May. Monocrop soybeans were generally planted in late April or early May. The difference in yield for the duration of the experiment averaged about 3.6 bushels per acre. Although the double-crop soyabeans had lower average yields, this system also had additional income from the wheat crop. Wheat yields ranged from about 40 to almost 80 bushels per acre and averaged 58 bushels per acre from 2002 through 2009. For most of the years, the double-crop system produced higher net returns than soyabeans alone. During the experiment, the double-crop system net returns were 58.89 dollars per acre higher than the monocrop soybeans. Based on this analysis, double cropping soybeans and wheat could add significantly to a producer's net income.