., 2012 ). In a concurrent study in the Salinas Valley conducted by the authors, a winter-killed cover crop (similar to the Partial-season treatment) on listed (peaked, unshaped) beds dramatically reduced runoff, and nutrient and sediment loss (unpublished
Aaron Heinrich, Richard Smith, and Michael Cahn
Orion P. Grimmer and John B. Masiunas
Winter-killed cover crops may protect the soil surface from erosion and reduce herbicide use in an early planted crop such as pea (Pisum sativum). Our objective was to determine the potential of winter-killed cover crops in a snap pea production system. White mustard (Brassica hirta) produced the most residue in the fall but retained only 37% of that residue into the spring. Barley (Hordeum vulgare) and oats (Avena sativa) produced less fall residue but had more residue and ground cover in the spring. Greater ground cover in the spring facilitated higher soil moisture, contributing to higher weed numbers and weight and lower pea yields for oat and barley compared with a bare ground treatment. White mustard had weed populations and pea yields similar to the bare ground treatment. Within the weed-free subplot, no differences in pea yields existed among cover crop treatments, indicating no direct interference with pea growth by the residues. In greenhouse experiments, field-grown oat and barley residue suppressed greater than 50% of the germination of common lambsquarters (Chenopodium album) and shepherd's-purse (Capsella bursapastoris), while in the field none of the cover crop provided better weed control than the fallow.
J.M. Caprio, H.A. Quamme, and R. Berard
Winter freeze events, identified by horticulturists to lower yields or kill trees (estimates vary by year from 1000 to >200,000 trees), have occurred in the Okanagan Valley of British Columbia 18 times in 94 years (1 in 5 years). To determine the association of winter temperatures and production, 72 years (1920–91) were separated into quartiles by level of production. Then, a maximum χ2 value was produced by a scanning iterative technique comparing each of the extreme quartiles with the combined mid-quartiles. A strong association was found between level of production and the low minimum temperatures in November, December, and February but not January. This result agrees with the historical records that indicate three winter-kill events occurred in November, five in December, one in January, and three in February during the same time period. Warm temperatures in September were associated with low production, indicating the possibility that warm temperatures at this time delay acclimation. Warm temperatures in January also were associated with low production, indicating a possible effect in hastening deacclimation.
Francis X. Mangan and Stephen J. Herbert
Field research was conducted in Deerfield, Mass. to study the effects of leguminous cover crops on sweet corn yield. Oat was planted alone and in combination with four leguminous cover crops August 8, 1990. Cover crop residue was disked once and sweet corn seeded April 23, 1991. Each cover crop combination had three rates of nitrogen added in two applications. Sweet corn seeded into stands of hairy vetch (Vicia villosa) yielded the highest of the cover crop combinations. All leguminous cover crop treatments yielded higher than oat alone or no cover crop when no synthetic nitrogen was added. Cover crop combinations were seeded again in the same field plots August 12, 1991. Oat biomass in November was greater where there had been leguminous cover crops or high rates of synthetic nitrogen. Legume growth was retarded in the plots that had previously received high nitrogen. It is thought that legume growth was reduced in the high nitrogen treatments due to increased oat growth and higher soil nitrogen levels which could inhibit root nodulation.
Edward Bush, Paul Wilson, Dennis Shepard, and James McCrimmon
An experiment to determine the nonstructural carbohydrate composition and nodal survival (LT50) of common carpetgrass was conducted between 1993 and 1994 at Baton Rouge, La. Nonstructural carbohydrates in stolons were primarily sucrose [70-130 mg·g-1 dry weight (DW)] and starch (8-33 mg·g-1 DW). Total nonstructural carbohydrate (TNC) composition of stolons ranged between 30 to 165 mg·g-1 DW. Node survival following exposure to 2 °C ranged from 0% in August-sampled grass to 48% in December. The LT50 following acclimation under field conditions was -2 to -4 °C. Environmental factors influenced nonstructural carbohydrate composition, partitioning, and node survival. No relationship between TNC concentration and low-temperature tolerance was found. This research confirms previous reports that low-temperature tolerance of carpetgrass is very poor, and its culture may be limited to geographical areas having moderate winter temperatures.
Hilary A. Sandler
The benefit of applying an antitranspirant for protection of cranberry (Vaccinium macrocarpon Ait.) vines exposed to desiccating conditions was evaluated at four different sites, two sites per year, for a period of 1 year each. Overall, plots receiving one fall application of an antitranspirant produced more berries and greater total fruit mass the following year than did nontreated plots. Overall dry leaf mass was not significantly affected. At one site, treated plots had more flowering uprights and more flowers per upright per unit of ground area than the nontreated plots. For cranberry growers who cannot maintain a winter flood, one fall application of pinolene (Vapor Gard) may offer some protection against winter injury. Further research is needed to document long-term yield effects as well as to clarify the role of the antitranspirant in protecting exposed vines and floral buds against adverse winter conditions. Chemical name used: di-1-p-menthene (pinolene).
Kerrie B. Badertscher and Harrison G. Hughes
Renewed interest in red raspberry production in Colorado has been limited by winter kill of canes. Winter kill in Colorado may be the result of extreme cold temperatures, desiccation, or a combination of the two. We are evaluating winter protection strategies to increase survival and to better understand the winter stress of raspberries. The four (4) cane treatments of red raspberry, Rubus ideaus L. cv. Heritage, used were (1) canes bent and wrapped with plastic; (2) canes bent and mulched with hay and soil; (3) canes upright with anti-desiccant spray; (4) a control of canes upright without protection. Moisture content and electrolyte leakage were evaluated at intervals. Relative moisture loss was greatest in the control as compared to the other treatments. The terminal sections of the canes exhibited greater moisture loss as compared to basal sections in the control with a similar trend in the other treatments. Relative survival as indicated by electrolyte leakage was monitored and will be correlated with moisture loss.
Orion P. Grimmer and John B. Masiunas
Winter-killed oats (Avena sativa) may have potential for use to suppress weeds in early seeded crops such as pea (Pisum sativum). Residue biomass and surface coverage are generally correlated with weed suppression. Oat residues also contain allelochemicals. Our objective was to determine if oat cultivars vary in residue production and allelopathy. Differences between oat cultivars were observed in residue production, and for effects on emergence of common lambsquarters (Chenopodium album) and shepherd's-purse (Capsella bursa-pastoris) in the greenhouse, and germination of pea and common lambsquarters in an infusion assay. Two of the oat cultivars producing the greatest biomass, `Blaze' (in the field) and `Classic' (in the greenhouse), interfered minimally with pea germination and were among the best cultivars in inhibiting common lambsquarters and shepherd's-purse. `Blaze' also greatly inhibited common lambsquarters germination in the infusion assay that measured allelopathy. Thus, `Blaze' and `Classic' possess suitable characteristics for use as a cover crop preceding peas.
Vegetable growers in the northeastern United States who want to use cover crops are limited by the relatively short growing season and by a lack of cover crop species options. Seven cover crops that winter-kill under NE US conditions were evaluated in on-farm trials for their suitability for following early harvested vegetables. Plots of oilseed radish (Raphanus sativus), white senf mustard (Brassica hirta), phacelia (Phacelia tanacetifolia), oats (Avena sativa), and a bare control were planted on 25 Aug. and 8 Sept. 1993, following a lettuce crop. In the early planting, oilseed radish, white senf mustard, and phacelia produced more than 3000 kg·ha–1 dry matter in 11 weeks, while oats produced just more than 2000 kg·ha–1. A smaller proportion of the accumulated biomass from these cover crops remained on the surface in the spring compared to oats. In the first planting, 80–107 kg·ha–1 N were accumulated in the above-ground biomass of the cover crops. On 3 and 16 Sept. 1994, plots of oilseed radish, white senf mustard, oats, yellow mustard (Brassica hirta), forage kale (Brassica oleracea), forage turnip (Brassica rapa), canola (Brassica napus cv. Sparta), and a bare control were established following potatoes. All cover crops except kale produced more than 3800 kg·ha–1 dry matter by late November in the early planting.