Agronomy Journal

Changes in tillage methods to cope with the continual erosion of our soil resource prompted the need to reassess current management practices for annual cropping systems of wheat (Triticum aestivum L.). A field study was conducted on Bethany silt loam (fine, mixed, thermic Pachic Paleustoll) from 1983 through 1987 near El Reno, OK to determine whether 10 hard red winter wheat cultivars respond differently to tillage systems. The cultivars were planted in moldboard‐plowed seedbeds, stubble‐mulch‐tilled seedbeds, or directly in standing stubble (no‐tillage). The effects of tillage method on plant stand, phenology, grain yield, and yield components were determined. Tillage method ✕ cultivar interactions varied with agronomic traits and years. In general, reducing tillage intensity delayed plant maturation beginning in the spring. Anthesis and leaf‐area duration periods occurred about 1 to 8 d later in mulch‐tilled and no‐tilled plots, compared with plowed plots. The prolonged vegetative phase indicated a potential benefit of no‐tillage in a wheat‐production system that includes a livestock grazing component during the winter months. Grain‐fill periods of no‐tillage wheat increased between 1 to 4 d in early‐maturity cultivars while those of later‐maturity cultivars were variable. The lack of tillage method ✕ cultivar interaction for grain yield indicated that development of wheat cultivars for emerging conservation technology may not be necessary. Notillage wheat yields were similar to conventional‐tillage yields, or slightly better in years with cold autumns that had erosive rains or dry springs. Early maturity cultivars consistently had stable yields during 1983 to 1987 with good resilience against environmental variations, but late‐maturity ones may not be suitable for no‐tillage winter wheat production. High temperature tolerance may be a potential breeding objective for plant types adapted to conservation tillage in the Southern Plains.

Inadequate amounts and distribution of rainfall are most often the major limiting factors to crop production in the southern Great Plains. This is especially true for summer crops, whether grown in mono‐ or double‐cropping situations. This study was conducted at the Oklahoma Vegetable Research Station, Bixby, OK from 1976 to 1987 on a Wynona silt loam soil (Cumulic Haplaquolls) with 0 to 1% slope. The objective was to determine the effects of long‐term double‐cropping on the potential for sustaining grain yields of wheat [Triticum aestivum (L.) em. Thell], soybean [Glycine max (L.) Merr.], and grain sorghum (Sorghum bicolor L. Moench) produced on the same land under rainfed conditions. Over a 12‐yr period monocropped wheat averaged 3050 compared with 2510 and 2450 kg ha⁻¹ when double‐cropped with soybean and grain sorghum, respectively. Conventionally tilled monocropped soybean and grain sorghum and no‐till double‐cropping of both soybean and grain sorghum after wheat produced grain 11 out of 12 yr. Monocropped soybean averaged 2470 compared with 1930 kg ha⁻¹ for no‐till double‐cropped soybean. Monocropped grain sorghum averaged 5130 compared with 4200 kg ha⁻¹ for double‐cropped grain sorghum. During the years of near 30‐yr average rainfall amounts and distribution (5 out of 11), yields of double‐cropped soybean and grain sorghum were competitive with those of monocropped soybean and grain sorghum. These results indicate that yields of double‐cropped wheat, soybean, and grain sorghum can be sustained over long periods of time. In eastern Oklahoma double‐cropping on a deep medium textured soil produced more total grain that resulted in more efficient use of climatic, land, labor, and equipment resources when compared with monocropping.

Municipal solid waste compost (MSWC) can enhance soil organic matter and crop nutrient supply. High C:N ratio composts can temporarily deplete plant‐available soil N reserves, requiring supplemental N fertilization to ensure optimum crop growth. The objective of our research was to measure seasonal soil NO₃–N dynamics to serve as an indication of N mineralization, immobilization, and leaching as affected by MSWC and N fertilizer rates. The MSWC (C:N 40:1) was applied in one year only to a Galestown sand (sandy, siliceous, mesic Psammentic Hapludults) at rates of 0, 63, 126, and 189 Mg ha⁻¹ Maize (Zea mays L.) was planted and N fertilizer rates of 0, 168, 336, 504, and 672 kg ha⁻¹ were applied as split‐plot treatments. First‐year maize total dry matter production plateaued at the 250 kg ha⁻¹ N rate, averaged across MSWC rates. Soil NO₃–N decreased inversely proportional to MSWC rates, due to MSWC immobilization of soil and fertilizer N. Cereal rye (Secale cereale L.) winter cover crop total dry matter yield and total crop N increased linearly with increasing MSWC rates. Second‐year maize total dry matter, total plant N, maize grain yield, and grain N increased linearly with increased MSWC rates applied the first year. During the second growing season, there was an increasing supply of plant‐available N, due to mineralization of organic N in the MSWC with increasing MSWC rate; however, the supply of mineralized N was inadequate to meet crop growth requirements for maximum maize yield.

Recent legislative actions addressing concerns about water and air quality have placed restrictions on open field burning and other grass seed production practices. Because of natural resource quality concerns and economic pressures, there is a need to identify production systems that protect natural resources while still providing economic returns to grass seed farmers. A 10‐yr field study was conducted at three locations in western Oregon. We compared the effects of direct seeding (DS) with conventional tillage (CT) establishment, combined with maximal (HR) and minimal (LR) residue management, on seed yield, straw phytomass yield, partial budget costs, and estimated soil erosion from perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.), and creeping red fescue (F. rubra L.). Perennial ryegrass (PRG) and tall fescue (TF) seed yields were greater using DS, whereas creeping red fescue (CRF) yields were unaffected. Seed yield from all three crops was unaffected by residue management amount. Both DS and HR reduced soil erosion and cost less to implement than CT and LR by straw baling and removal. Compared with the industry standard practice of LR management plus CT establishment, use of HR combined with DS reduced soil erosion 76.9, 70.2, and 40.0% for PRG, TF, and CRF, respectively. The cost savings using the DS‐HR conservation system compared with the CT‐LR farm standard were 60, 76, and 84%, respectively. It was also observed that nonmarket opportunities have resulted from implementation of the alternative conservation practices. These research findings document the suitability of DS used in combination with HR in maritime Pacific Northwest region perennial grass seed production systems without needing postharvest straw removal.

In an effort to protect field corn (Zea mays L.) from wireworm (Agriotes obscurus L.) herbivory and yield loss, seeds were treated with conidia of Metarhizium anisopliae strain F52 alone or in combination with clothianidin or spinosad before planting at three farm fields in south coastal British Columbia, Canada. Corn seed treated with M. anisopliae conidia (main effect) resulted in significant increases in stand density (78% M. anisopliae treated vs. 67% no M. anisopliae) and stock and foliage area fresh wt. yield (9.6 Mg ha⁻¹ M. anisopliae treated vs. 7.6 Mg ha⁻¹ no M. anisopliae), and significantly increased plant (stock and foliage) fresh wt. when it was applied together with spinosad or with no additional agrichemical at one location. Spinosad had no effect on corn yield, whereas clothianidin caused a significant increase in plant stand density and yield. Wireworm cadavers showing M. anisopliae strain F52 growth were retrieved from treated plots, suggesting that the increase in yield may have been due to wireworm control. Laboratory experiments provided no evidence that the increase in stand density and yield from the M. anisopliae‐treated corn seed was attributable to an increase in germination rate or root growth. We concluded that seed treatment with this fungus may be a novel method to increase stand density and yield of corn.

Nitrogen is the most limiting nutrient for crop production on the northern Great Plains of North America. This study was initiated to determine if N yield and land use efficiency for N could be improved by manipulating crop diversity using three annual crops (wheat, Triticum aestivum L.; canola, Brassica napus L.; and field pea, Pisum arvense L.) commonly grown on the Canadian Prairies. The study included all combinations of the crops (sole crops and intercrops) and compared their effects on soil N depletion, plant N concentration, plant N yield, and land equivalent ratios for dry matter and grain N yield (NLER) at two field sites in Manitoba, Canada. The pea sole crop treatment tended to result in higher fall soil nitrate (NO₃⁻)–N concentrations compared to other treatments, indicating greater potential for post‐season NO₃⁻ leaching after this treatment. There were often greater N concentrations in wheat, canola, and weeds when grown in association with field pea, suggesting that soil N could have been made available for nonlegume uptake through the NO₃⁻–N sparing effect On average, most intercrop treatments resulted in more efficient land use for N compared to component sole crops, with overall mean intercrop NLER values ranging from 1.10 to 1.20. The wheat–canola–pea and canola–pea intercrop treatments tended to produce the highest and most consistent NLER values for crop dry matter and grain yield, respectively. The results of this study suggest that intercrops could be used for more efficient use of N on a per land area basis.

Maintaining current high yields of corn (Zea mays L.) grown in the USA poses an environmental threat due to continued overuse of water and N inputs. To reduce overreliance on inputs, future corn breeding efforts should focus on improving tolerance of corn to water and N stresses, utilizing appropriate tolerance mechanisms. The objective of this study was to identify appropriate mechanisms by characterizing agronomic responses of 12 hybrids from three different eras (‘B73 × Mo17’ from 1970s and three early 1990s and eight late 1990s Pioneer brand hybrids) to varying water and N supply. This was done by growing the hybrids under deficit and adequate levels of water (one‐half and full evapotranspiration) and N (0 and 200 kg ha⁻¹) in a field study and measuring yield and other agronomic variables. While hybrid eras didn’t differ in response to varying water or N, individual hybrids varied in ability to maintain yield under water or N stress. For example, under deficit water, ‘3417’ produced 27% more yield than ‘3162’ while they yielded similarly under adequate water. Likewise, under deficit N, ‘34R07’ produced 42% more grain yield than ‘33G27’ while they yielded similarly under adequate N. Agronomic variables such as kernel number per unit area were highly correlated with grain yield (r = 0.98), indicating hybrid ability to maximize kernel number under varying water and N supply was critical to maximizing yield. Determining physiological mechanisms associated with ability to maintain kernel number under stress should be a high priority of breeding programs.