Organic weed control in direct seeded vegetables depends on management strategies that control weed germination or growth which depletes the weed seedbank. In 2004, a randomized complete-block experiment conducted on land transitioning to organic production examined the effects of tillage and control treatments on weed pressure in sweet corn [Zeamays (L.) cv. Silver Queen]. The two tillage treatments consisted of conventional (moldboard and rototill) and spader tillage. Weed control treatments included a weed free control, a spring-tine weeder, rolling cultivator, row flamer, stale seedbed, and corn gluten meal. In August, the weed infestation was primarily goose grass [Eleusineindica (L.) Gaertn.], crab grass [Digitariasanguinalis (L.) Scop.], giant foxtail (Setariafaberi Herrm.), and smooth pigweed [Amaranthushybridus (L.)] species. Dried weed weights indicated that smooth pigweed constituted about 80% of the total weed biomass in all but the control and flamer treatments. Plots managed with the spring-tine weeder or corn gluten had twice the weed biomass of those managed with the rolling cultivator and flamer. The rolling cultivator and control treatments produced equivalent husked corn yields (6.9 t·ha-1); yields were reduced by the other weed control methods. At 5.4 t·ha-1, yields in the flamer treatment were the lowest among all weed control methods. The flamer suppressed both weeds and the crop, which may preclude its utility for sweet corn production. Results demonstrated that the rolling cultivator provided the best weed control without negatively affecting potential yields.
Paul W. Bosland
Chile pepper (Capsicum spp.) hybrids are normally produced by hand-emasculating the female parent and then pollinating the emasculated flower by hand. Increased yield has occurred with F1 hybrid seed, but the seed is considered too expensive by growers to be direct-seeded, a common production practice in the southwestern U.S. chile pepper industry. In ornamental flowers, when F2 hybrid seed is available, it is cheaper than F1 hybrid seed. If F2 hybrid chile pepper cultivars could manifest heterosis, and produce fruit quality acceptable to the chile pepper industry, then a less-costly alternative would be available to growers. A series of field trials with jalapeños was conducted to test F1 hybrid cultivars to their F2 progeny for yield and fruit quality. The results indicated that in some instances the F2 progeny can yield as well as the F1 hybrid parent. Therefore, F2 hybrid cultivars can be used in a commercial production system. However, if a male-sterility system is used to produce the F1 hybrid cultivar, the F2 progeny will have significantly lower yield than the F1 hybrid parent, as was the case in one accession in this trial. Nevertheless, F2 hybrid cultivars are an additional way to supply high yielding hybrid cultivars to growers.
Thomas Björkman and Joseph W. Shail Jr.
Establishment of a weed-suppressive cover crop after vegetables harvested early in the season is important in the northeastern United States because of the short growing season. Buckwheat (Fagopyrum esculentum) is an effective cover crop in vegetable production because of its short growing season, ability to outcompete many weeds, resistance to damage by insects and disease, and requirement for only moderate soil fertility. In two separate 3-year field experiments, we determined the best tillage techniques and the optimal timing for use of buckwheat as a cover crop after early vegetables in the northeastern United States. Incorporating crop residue with a disk was necessary and provided sufficient tillage to obtain a weed-suppressive buckwheat stand. Buckwheat growth was stunted when direct seeded with a no-till drill immediately after pea (Pisum sativum) harvest because of poor soil penetration by buckwheat roots. Planting buckwheat after incorporating the pea crop was successful; waiting 1 week to plant was optimal, whereas a 2-week wait produced a weaker stand. We determined that optimal timing for sowing buckwheat in central New York was late June to early August. Generalizing to other geographical regions in the United States, we calculated that a minimum accumulation of 700 growing degree days is necessary to reach 1 to 1.5 tons/acre of buckwheat dry matter at the appropriate growth stage for incorporation (6 weeks after sowing).
J. Irizarry-Morales, L. Wessel-Beaver, D. Maynard, and G. Elmstrom
Three field experiments were carried out in Lajas, Puerto Rico, to compare the effects of planting method (direct and transplant), plastic mulch (with and without), and planting density (1.8 x 1.8 m, 3.6 x 0.9 m, 1.8 x 0.9 m between and within rows) on production of short-and long-vined tropical pumpkins (Cucurbita moschata). The long-vine genotype produced greater yields and larger but fewer fruit than the short-vine genotype. However, most of the planting densities tested were probably not optimum for short-vine cultivars. Direct seeding of pumpkin was more efficient than transplanting and resulted in the same early and total yield as transplanting. Yields with plastic-covered banks were similar to yields without the use of plastic. However, use of plastic mulch increased the number of fruit and decreased the average fruit weight in the plots. The best planting distance depended on the type of genotype used. The long-vine genotype had the highest yields at 1.8 x 1.8 m, while the short-vine cultivar performed best with half that amount of space per plant (1.8 x 0.9 m). Production of short-vine cultivars might be improved by using even narrower planting distances.
Muddappa Ranqappa, Harbans Bhardwaj, and Madeha Showhda
Two experiments, one each with cilantro and dill, were conducted during 1994 to determine optimum rates of N, P, and K fertilizers. In these experiments, `C1410' cilantro and `Bouquet' dill were direct seeded in three-row plots with 0.3-m spacing between rows. A seeding rate of ≈40 seeds per meter of row length was used. Data were recorded, 45 days after planting, on moisture content, chemical composition of foliage (contents of essential oils, protein, and ash), and fresh yield following 25, 50, 75, and 100 kg·ha–1 application of each nutrient (4 × 4 × 4 factorial). Nitrogen rates significantly affected moisture, ash, and fresh yield of cilantro and dill. Phosphorus rates significantly affected moisture content and yield of dill but not cilantro. The effects of K applications were nonsignificant. The optimum N rate for both cilantro and dill was 25 kg/h. The optimum rate of P for dill was 25 kg/h. The data indicated that N and P requirements of cilantro and dill are modest. Further details of these results will be presented and discussed.
J. Pablo Morales-Payan* and William M. Stall
A field experiment was conducted in Live Oak, Fla., to determine the effect of yellow nutsedge (Cyperus esculentus L.) (YN) density and time of emergence on the yield of direct-seeded squash (Cucurbita pepo L.). YN densities (0, 20, 40, 60, and 100 plants/m2) were established from tubers planted at different times onto polyethylene-mulched beds, so that YN would emerge the same day as the crop or 5, 15, or 25 days later than the crop (DLTC). YN was not controlled after its emergence. The extent of squash yield loss was affected by YN density and time of emergence. When YN emerged the same day as the crop, the yield of squash was reduced by ≈7% (20 YN/m2) to 20% (100 YN/m2). When YN emerged 15 DLTC, crop yield loss was ≈13% at the density of 100 YN/m2>. Regardless of density, YN emerging 25 DLTC did not significantly reduce crop yield as compared to weed-free squash. Thus, in soils with high YN densities (≈100 viable tubers/m2) herbicides and/or other means of YN suppression in squash should be effective for at least 25 days after crop emergence to prevent significant yield loss. If squash yield losses <5% were acceptable, YN control may not be necessary when densities <20 YN/m2 emerge at any time during the squash season or when <100 YN/m2 emerge >25 DLTC. However, YN emerging during the first 15 days of the squash season may produce tubers, which could increase the YN population at the beginning of the following crop season.
Lynn P. Brandenberger*, Lynda K. Wells, and Bruce B. Bostian
The objectives of this trial were to collect yield and quality data on a fall planted carrot trial. Fifteen different carrot varieties were included in the trial. Plots were 20 feet by 2.5 feet and consisted of two rows of carrots with 15-inch row centers. Plots were replicated 4 times in a RBD. Carrots were direct seeded on 8 Aug. 2003 at 20 seeds per foot. Plots were fertilized with 90 lbs/acre of nitrogen and received overhead water as needed. Yield and quality data were recorded on 5 Dec. 2003. Data included exterior root color, interior root color, percentage of split and forked roots, overall yield, average root length and weight. Exterior root color did not vary significantly for any of the cultivars in the trial, but interior root color varied significantly for several cultivars. `First Class', `Bolero', and `C 7105' had the most distinct differences between the pith and out ring colors as indicated by the interior root color ratings and `Ingot' had the lowest. Interior root color ratings for these four cultivars were 3.8, 3.6, 3.1, and 1.4, respectively. Crispness did not vary for either the initial or second ratings that were recorded. Of potential defects only the percentage of forked roots varied significantly and of these four cultivars had less than 10% forked roots. `Florida', `Kamaran', `Pipeline', and `C 7105' had 5%, 7%, 9%, and 9% forked roots, respectively. `Samantha' had 31% forked roots, the highest percentage recorded in the trial. No differences were recorded for root weight, diameter or length. The three highest yielding cultivars in the trial were `Ingot', `Heritage', and `Neptune' that had overall yields of 24.9, 20.6, and 20.6 tons/acre. `Bremen' recorded the lowest yield in the trial with 13.7 tons/acre.
Brian A. Kahn, Niels O. Maness, Donna R. Chrz, and Lynda K. Carrier
Field experiments were conducted at Bixby, OK, in 2007. Four compost treatments and an unamended control were compared for field production of eight (spring) or four (fall) red radish (Raphanus sativus L.) cultivars. Treatments were either spent mushroom substrate or yard waste compost spread over plots to an average depth of 2.5 or 5 cm and preplant-incorporated ≈5 to 7 cm deep. Radishes were direct-seeded into prepared plots and subsequently grown using standard cultural practices. Samples of median-sized marketable storage roots were shredded and juice was analyzed in the laboratory for pungency as measured by isothiocyanate (ITC) concentration (primarily 4-methylthio-3-butenyl isothiocyanate). In the spring, mean ITC concentrations ranged from 28.2 to 36.8 μmol per 100 g juice in storage roots from the four compost treatments, and differences were not significant (α = 0.05). There were not enough storage roots to analyze from the unamended control plots as a result of herbicide toxicity. Cultivars differed in mean concentration of ITCs, ranging from a high of 52.9 μmol per 100 g juice for ‘Cherry Belle’ to a low of 19.2 μmol per 100 g juice for ‘Crunchy Royale’. In the fall, mean ITC concentrations ranged from 10.5 to 24.6 μmol per 100 g juice in storage roots from the four compost treatments. Differences were not significant (α = 0.05), and there were no differences from the control value of 17.5 μmol per 100 g juice. The mean ITC concentration was 19.9 μmol per 100 g juice for the four cultivars tested in the fall, and the cultivars did not differ. Results indicate that the tested compost treatments did not affect pungency of red radish storage roots as measured by concentrations of ITCs.
Chandrappa Gangaiah, Amjad Ahmad, Hue V. Nguyen, Koon-Hui Wang, and Theodore J.K. Radovich
The application of locally available invasive algae biomass as a fertilizer for crop production in Hawaii is being investigated as a substitute for imported chemical fertilizers. Three closely related greenhouse trials were conducted to determine if the algae served as a source of potassium (K) on growth, yield, and K mineral nutrition in pak choi (Brassica rapa, Chinensis group). In the first trial, three algal species (Gracilaria salicornia, Kappaphycus alvarezii, and Eucheuma denticulatum) were applied at five rates of K, each to evaluate their effects on growth and K nutrition of pak choi plants. The pak choi was direct seeded into 0.0027-m3 pots containing peatmoss-based growth media. In trial 2, pak choi was grown in peat media at six rates of K provided by algae (E. denticulatum) or by potassium nitrate (KNO3). In trial 3, the six rates of K were provided through algae (K. alvarezii), KNO3, and potassium chloride (KCl) and were compared for growth and K nutrition. Results from the first greenhouse trial showed no significant differences among the three algal species in yield or tissue K content of pak choi. However, plant yield and tissue K concentration were increased with application rates. The maximum yield and tissue K were observed when K was provided within the range of 250–300 kg·ha−1. Similarly, in Expts. 2 and 3, there were no significant differences between commercial K fertilizers and algal K species for yield. Only K rates were significant for yields and tissue K concentrations. It was concluded that K in the invasive algae was similarly available as K in commercial synthetic fertilizers for pak choi growth in terms of yield and tissue K content under our experimental conditions.
Elizabeth T. Maynard
Benefits of drip irrigation for jack-o-lantern pumpkins (Cucurbita pepo) in the midwestern United States are not documented. Field trials were conducted on a sandy loam soil to compare yield and fruit size of unirrigated pumpkins (NONE) with pumpkins irrigated when in-row soil water tension (SWT) 30 cm deep reached 20 kPa (HIGH) or 60 kPa (MED). The 2004 trial included two planting methods, direct seed (SD) and transplant, and two cultivars, `Gold Medal' (GM) and `Magic Lantern' (ML). GM typically has larger and more vigorous vines than ML. In 2005 the trial included only SD ML. Rainfall June through August totaled 38.4 cm in 2004 and 28.2 cm in 2005. In 2004 HIGH increased yield 13% compared to NONE (42.1 vs. 37.2 t·ha-1). MED (39.0 t·ha-1) did not differ from NONE. Neither planting method nor cultivar influenced the yield response to irrigation. The effect of irrigation on average weight per pumpkin depended on cultivar. In 2004, ML with HIGH averaged 7.76 kg per pumpkin, 16% heavier than NONE at 6.67 kg. MED averaged 7.17 kg. Irrigation did not affect average weight of GM: HIGH, MED and NONE averaged 12.6, 12.8 and 12.3 kg, respectively. For SD ML, combined analysis of 2004 and 2005 data showed an 18% increase in average pumpkin weight for HIGH vs. NONE (7.94 vs. 6.72 kg), but no significant effect of irrigation on yield (33.6, 29.8 and 28.4 t·ha-1 for HIGH, MED and NONE, respectively). Irrigation did not affect the number of pumpkins produced per hectare for either cultivar in either year. Results suggest that compared to no irrigation, maintaining SWT less than 20 kPA with drip irrigation may lead to 1) yield increase on the order of 10% or less, 2) 16% to 18% increase in average pumpkin weight for ML.