S. Alan Walters

Utility of Winter Rye Living Mulch for Weed Management in Zucchini Squash Production

Abstract The extended production of allelochemicals from a living mulch cover crop may potentially enhance weed management and crop productivity compared with traditional zucchini squash production systems. However, the efficacy of a living mulch cover crop in no-tillage (NT) systems with herbicides has not been determined for many vegetable crops. The objective of this research was to evaluate weed management and zucchini squash production using the combination of NT and a herbicide-suppressed winter rye cover crop with or without PRE herbicides. When used in combination with herbicides, the winter rye living mulch reduced the biomass of redroot pigweed compared to the herbicides applied alone, but did not influence the biomass of smooth crabgrass for any herbicide treatment. Visual estimates of weed control were similar for each herbicide treatment with and without the winter rye living mulch. The herbicide-suppressed winter rye resulted in excessive stunting of zucchini squash at 56 d after treatment which correlated with 20 and 50% squash yield reductions for the 2004 and 2005 growing seasons, respectively. Although some squash yield loss may have resulted from direct competition with the winter rye living mulch, yield reductions most likely resulted from allelopathy. The winter rye living mulch was the primary contributing factor for reduced squash yield and did not interact with herbicide treatment. All treatments containing herbicides resulted in yields similar to the weed-free treatment. Because of excessive zucchini injury, this research suggests that the use of herbicide-suppressed winter rye living mulch does not appear to be a feasible option for increased weed control in zucchini squash production regardless of the herbicide treatment. Nomenclature: Clethodim; clomazone; dimethenamid; ethalfluralin; imazamox; redroot pigweed, Amaranthus retroflexus L. AMARE; smooth crabgrass, Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl. DIGIS; winter rye, Secale cereale L. ‘Wheeler’; zucchini squash, Cucurbita pepo L. ‘Independence II’

Optimum planting density and harvest stage for little-leaf and normal-leaf cucumbers for once-over harvest

Optimum planting density and harvest stage were determined for once-over harvest of little-leaf and normal-leaf cucumbers. Three harvest stages (10, 25, and 50% oversize fruit) and four plant densities (37,000, 75,000, 150,000, and 300,000 plants/ha) were evaluated on little-leaf cucumber (H-19) and normal-leaf cucumber (Sumter and Regal). Plant density did not affect skin color, seedcell size, and seed size in the cultivars evaluated. However, lighter skin color, larger seedcell, and larger seed size were detected at the later harvest stages in H-19. Harvest stage did not influence fruit skin color in Regal and Sumter, but seedcell size and seed size increased quadratically with harvest stage. H-19 produced the highest yield (tonne/ha) and dollar value (

Influence of Tillage, Cover Crop, and Preemergence Herbicides on Weed Control and Pumpkin Yield

/ha) followed by Regal and Sumter. Considering fruit quality and dollar value, the 10% harvest stage at 330 000 plants ha−1 was the optimum stage and density for once-over harvest of H-19 under North Carolina growing conditions. Higher yield occurred at ...

Water distribution systems and on-farm irrigation practices: limitations and consequences for Afghanistan's agricultural productivity

ABSTRACT Many Midwestern and Eastern U.S. jack-o-lantern pumpkin (Cucurbita pepo L.) growers are interested in using no-tillage production practices. However, improved weed management practices must be developed before no-tillage will be readily adopted for pumpkin production. A field study was conducted to determine effects of tillage, winter rye (Secale cereale L.), and preemergence herbicides on weed control and pumpkin yield. Grass and broadleaf weed control was greater in no-tillage compared to conventional tillage, and cover crop use in a no-tillage system further improved the level of weed control. Early- and late-season control of giant foxtail (Setaria faberi Herrm.), common cocklebur (Xanthium strumarium L.), redroot pigweed (Amaranthus retroflexus L.), and common waterhemp (A. rudis Sauer) were highly correlated (0.48 ≥ r ≤ 0.86, P ≤ 0.01) with pumpkin yield and fruit size. Although applying clomazone+ethalfluralin to winter rye residues improved broadleaf weed control compared with no herbicide, the level of control for all broadleaf species was unacceptable (∼86%) by 60 days after herbicide treatment (DAT), regardless of tillage treatment. However, addition of halosulfuron or imazamox to clomazone+ethafluralin generally improved redroot pigweed and common waterhemp control in no-tillage and conventional tillage compared with clomazone+ethafluralin alone; common cocklebur control was improved with addition of halosulfuron only to clomazone+ethafluralin. Although pumpkin fruit numbers in the weed-free control did not differ (P > 0.05) from tank mixtures of clomazone+ethalfluralin with halosulfuron or imazamox, reductions in pumpkin fruit size (30–35%) and yields (18–20%) were observed for these herbicide treatments compared with the weed-free control. This research indicates that cover crops, such as winter rye, can be successfully integrated in no-tillage pumpkin production systems along with herbicides to improve weed management.

Evaluation of the U.S. cucumber germplasm collection for root size using a subjective rating technique

The absence of a reliable water supply to farmers is the single most important impediment to food security and agricultural expansion in Afghanistan. Agricultural water supply and distribution systems are reviewed, and a pragmatic strategy is outlined to increase water capital and to better utilize available water. The development and dissemination of on-farm practices that improve water management through community-based approaches represent the best opportunity for improving farmer livelihoods, maintaining social stability and developing a sound agriculture-based economy in the immediate future, independent of the success or failure of national water policies.

Incompatibility in diploid and tetraploid crosses of Cucumis sativus and Cucumis metuliferus

SummaryRoot size in cucumber (Cucumis sativus L.) has received little research attention until recently. However, a large root system could improve nutrient and water uptake, and ultimately yield. Knowledge of root size could help cucumber breeders develop cultivars with improved performance. A study was conducted in the greenhouse to evaluate 857 cultigens (827 plant introduction accessions, 22 breeding lines, and 8 cultivars) of cucumber for root length. Complete data were obtained for 794 cultigens. Plants were grown from seeds in 2 replications in the greenhouse. Plants were rated for root length using a 1 to 9 scale (1–3 = small, 4–6 = medium 7–9 = large). Also, root length was measured from soil surface to the tip of the longest main root. In addition, all cultigens were evaluated for root length and dry weight to provide meaning to the subjective rating. Root rating was highly correlated with both root length (r=0.92) and dry weight (r=0.64) of roots. Root length averaged 74 mm and most cultigens (579, or 68%) had roots 40 to 110 mm long. The cultigen with the longest roots was PI 183056 (193 mm), and the shortest was PI 176954 (2 mm). The subjective rating technique provided a simple, accurate and rapid method to estimate root growth in the greenhouse.

Effects of Adjuvants, Halosulfuron, and Grass Herbicides on Cucurbita spp. Injury and Grass Control

The African horned cucumber (Cucumis metuliferus Naud.; 2x = 2n = 24) contains genes that can confer resistance to many important cucumber (C. sativus L.; 2x = 2n = 14) pests [e.g., root-knotnematode, Meloidogyne incognita (Kofoid & White) Chitwood]. Cucumber is highly susceptible to this root-knot nematode species, and a recent screening of C. sativus accessions in the U.S. National Plant Germplasm collection did not identify sources of resistance. Thus,autotetraploids of Cucumis sativus and C. metuliferus were created to recover fertile resistant interspecific progeny. Autotetraploids were obtained at the highest rate when seeds were immersed in 0.5% colchicine for a period of 6 to 8 hrs. Treatment durations less than 6 hrs produced few tetraploids, and durations of 10 hrs or more were lethal to seeds or developing seedlings. Crosses between C. sativus and C. metuliferus were made using diploid and tetraploid lines in all possible combinations, including reciprocals. Fruit development occurred in crosses when diploid and tetraploid C. sativus were used as the female parent. However, seeds developed only in fruit of C. sativus (4n) ×C. metuliferus (2n) crossings. Seeds from these crosses, however,were flat and not viable. No fruit development occurred in crosses whereC. metuliferus was used as the female parent.

Cover Crop and Pre-Emergence Herbicide Combinations in No-Tillage Fresh Market Cucumber Production

Abstract Greenhouse experiments were conducted to evaluate pumpkin cultivar injury and control of three grass species from tank-mixtures of halosulfuron with either clethodim or sethoxydim in combination with nonionic surfactant (NIS), crop-oil concentrate (COC), methylated seed oil (MSO), and high-surfactant oil concentrate (HSOC). Pumpkin injury, in the form of chlorosis and visual growth reduction, was 13 to 21% by 7 d after treatment (DAT) for all pumpkin cultivars. The specific adjuvant used with halosulfuron did not influence pumpkin injury or final plant dry weight. Pumpkin growth reduction at 21 DAT from halosulfuron was less than 9% for all pumpkin cultivars with the least growth reduction (5% or less) observed with Cucurbita pepo ‘Howden’, C. pepo ‘Appalachian’, and Cucurbita moschata ‘Libbys Select’. The efficacy of sethoxydim or clethodim on large crabgrass was antagonized by the addition of halosulfuron with NIS or COC. However, only combinations of sethoxydim and halosulfuron with COC or MSO were antagonistic on smooth crabgrass. Giant foxtail dry weight reduction was decreased 4 to 24% by the addition of halosulfuron to sethoxydim with NIS and clethodim regardless of adjuvant. Although the frequency and magnitude of grass antagonism was variable, the use of clethodim and MSO with halosulfuron most often provided the greatest level of grass control compared with sethoxydim or other adjuvants.

Influence of Tillage and Mulching Systems on Soil Water and Tomato Fruit Yield and Quality

ABSTRACT A field study was conducted to determine the effect of various pre-emergence (PRE) herbicide (clomazone, ethalfluralin, and halosulfuron) combinations with or without a winter rye (Secale cereale L.) cover crop on control of smooth crabgrass [Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl.] and redroot pigweed (Amaranthus retroflexus L.) in no-tillage ‘Daytona’ cucumber (Cucumis sativus L.) production. Winter rye provided a significant advantage for weed control compared with the no-cover-crop production system. In the absence of herbicides, winter rye reduced redroot pigweed and smooth crabgrass densities up to 69 and 89%, respectively, compared with no winter rye at approximately 60 days after transplanting (DAT). Furthermore, the use of a winter rye cover crop increased the level of weed control achieved by herbicides at 56 DAT in two of three years for each weed species. Winter rye enhanced early marketable cucumber yields (from 2,008 to 6,100 kg·ha−1) under drought conditions in 2002, while winter rye suppressed early marketable yields (from 14,883 to 9,367 kg·ha−1 and 16,117 to 13,600 kg·ha−1 in 2003 and 2004, respectively) when sufficient moisture and cooler spring temperatures were present. During drought conditions in 2002, no-tillage treatments with clomazone + ethalfluralin and clomazone + ethalfluralin + halosulfuron produced similar yields; however, under high moisture and cooler conditions in 2003 and 2004, no-tillage treatments with clomazone + ethalfluralin + halosulfuron produced greater early- (∼16%) and total-season (∼25%) marketable yields than treatments with clomazone + ethalfluralin. Weed control is essential to obtain optimal cucumber productivity, as simple correlations indicated that cucumber yields were highly correlated to smooth crabgrass and redroot pigweed control. Cover crops, such as winter rye, can be integrated in vegetable production systems along with labeled herbicides as a sustainable approach to improved weed management.

Efficacy of Postemergence Corn and Soybean Herbicides on Volunteer Horseradish (Armoracia rusticana)

ABSTRACT Many growers have interests in using mulches, cover crops, and conservation tillage systems in tomato production, but also have concerns about the effect of soil moisture fluctuations on fruit quality. Percent soil moisture and ‘Fabulous’ tomato (Lycopersicon esculentum Mill.) fruit production in response to different mulching/tillage systems within wheat (Triticum aestivum L.) and winter rye (Secale cereale L.) cover crops were evaluated. Treatments applied following the mowing of the cover crops were: (1) conventional tillage (CT); (2) black polyethylene plastic over conventional tillage (BP); (3) no-tillage with cover crop killed with 1.5% glyphosate one week prior to transplanting (NT); (4) strip-tillage with cover crop killed with a 1.5% glyphosate one week prior to transplanting (ST); (5) no-tillage in which the cover crop was mowed periodically during the growing season [NT-Lm (living mulch)]; and (6) strip-tillage with the cover crop mowed and treated similar to treatment 5 (ST-Lm). Generally, there were no differences (P < 0.05) between winter rye and wheat cover crops with respect to tomato quality or yields. Large amounts of cull fruit were produced in both years, regardless of moisture; however, blossom-end rot was more severe across treatments during 1999. Under drought conditions (1999 growing season), all conservation tillage treatments had higher soil moisture readings 24 hrs after rainfall than other treatments, but BP had higher moisture levels than all other treatments under times of excessive water depletion. Under a condition of sufficient soil moisture (2000 growing season), black plastic resulted in higher soil moisture early in the season than CT or conservation tillage systems, a response associated with greater total marketable yields. Comparisons between the various conservation tillage treatments for soil moisture and tomato yields were inconclusive, but with adequate and consistent soil moisture, conservation and conventional tillage treatments produced similar marketable yields.