Growing a main vegetable crop for harvest and a cover crop for residue return to soil in the same growing season is a promising strategy to sustain soil quality in vegetable rotations. Our research evaluated cover crop strips interseeded between pumpkins (Cucurbita pepo L.) as a way to implement such a strategy. Cover crop types were lana vetch (Vicia villosa ssp. dasycarpa Ten.) and a lana vetch–winter rye (Secale cereale L.) mix, interseeded before, at the same time, or after pumpkins. The competitive impact of different cover crop strips was assessed using pumpkin yield, cover strip biomass, crop nitrogen status, soil nitrate status, and soil water potential. Cover strips were also assessed for competitiveness with native weeds. Seeding date affected the competitiveness of cover strips with pumpkins, while cover type did not. Cover crops seeded before pumpkins or at the same time reduced pumpkin yield in proportion to biomass produced by the cover strips early in pumpkin growth. Cover strips seeded after pumpkins did not reduce yield. Tilling in a before-seeded cover strip at 30 days after pumpkin seeding gave higher pumpkin yield than before-seeded cover strips that were not tilled. At three of four sites, after-seeded cover strips had the lowest percent weed biomass in strips, and at two sites with moderate weed pressure vetch–rye strips were more effective than vetch alone in suppressing weeds. Cover strips seeded before or at the same time as pumpkins reduced pumpkin yield by taking up resources that were otherwise available to pumpkins. At a high-rainfall site, competition for soil nitrate by cover crop strips was the dominant factor in reducing pumpkin yield. At a low-rainfall site, the dominant factor was competition for water. Because of effective weed suppression and lack of pumpkin yield reduction, interseeding vetch–rye strips after pumpkins was a promising practice, as was tilling in preexistent cover strips at an interval <30 days after pumpkin seeding. Good previous weed management and rye–vetch mixes at high seeding rates are necessary to allow interseeded cover strips to outcompete weeds.
Steven Vanek, H.C. Wien and Anu Rangarajan
T.K. Hartz, J.P. Mitchell and C. Giannini
Nitrogen and carbon mineralization rates of 19 manure and compost samples were determined in 1996, with an additional 12 samples evaluated in 1997. These organic amendments were mixed with a soil: sand blend at 2% by dry weight and the amended blends were incubated at constant moisture for 12 (1996) or 24 weeks (1997) at 25 °C. Net N mineralization was measured at 4- (1996) or 8-week (1997) intervals, C mineralization at 4-week intervals in 1997. Pots of the amended blends were also seeded with fescue (Festuca arundinacea Shreb.) and watered, but not fertilized, for 17 (1996) or 18 weeks (1997); N phytoavailability was estimated from fescue biomass N and mineral N in pot leachate. An average of 16%, 7%, and 1% of organic N was mineralized in 12 weeks of incubation in 1996, and an average of 15%, 6%, and 2% in 24 weeks of incubation in 1997, in manure, manure compost, and plant residue compost, respectively. Overall, N recovery in the fescue assay averaged 11%, 6%, and 2% of total amendment N for manure, manure compost, and plant residue compost, respectively. Mineralization of manure C averaged 35% of initial C content in 24 weeks, while compost C mineralization averaged only 14%. Within 4 (compost) or 16 weeks (manure), the rate of mineralization of amendment C had declined to a level similar to that of the soil organic C.
David Conner and Anusuya Rangarajan
overall agricultural land ( U.S. Department of Agriculture, 2008a , 2008b ). The market premiums that currently exist for many organic crops are an attractive incentive for conventional growers considering the transition to organic practices. Before
Angela K. Tedesco, Gail R. Nonnecke, John J. Obrycki, Nick E. Christians and Mark L. Gleason
Field plots of four production systems of `Tristar' dayneutral and `Earliglow' Junebearing strawberry (Fragaria xananassa Duch.) were established in 1993. Productions systems included conventional practices (CONV), best-management practices including integrated crop management (ICM), organic practices using corn gluten meal, a natural weed control product, (ORG-CGM), and organic practices using a natural turkey manure product (ORG-TM). `Earliglow' plants grown with ORG-CGM showed the highest number of runners and total vegetative biomass. Plots with CONV and ICM systems using standard herbicide treatments had lower total weed numbers (11 and 18, respectively) than ORG-CGM (63) and ORG-TM (58). `Tristar' plant growth, yield and berry number were reduced when plants were grown under straw mulch in ORG-CGM and ORG-TM compared to CONV and ICM plots with polyethylene mulch.
Angela K. Tedesco, Gail R. Nonnecke, Nick E. Christians, John J. Obrycki and Mark L. Gleason
Field plots of four production systems of `Tristar' dayneutral and `Earliglow' June-bearing strawberry (Fragaria ×ananassa Duch.), established in 1993, included conventional practices (CONV), integrated crop management practices (ICM), organic practices using granulated corn gluten meal, a natural weed control product, (ORG-CGM), and organic practices using a natural turkey manure product (ORG-TM). `Earliglow' total yield from CONV plots in 1994 was similar to ICM and ORG-CGM, but greater than ORG-TM. Average berry weight and marketable yield were greater in the CONV system than both organic systems. CONV, ICM, and ORG-CGM plots had more runners and daughter plants than ORG-TM. Plots with CONV herbicide treatments were similar to ICM and ORG-CGM for percentage weed cover 1 month after renovation. `Tristar' crown number, crown and root dry weights, yield, and berry number were reduced when plants were grown under straw mulch in ORG-CGM and ORG-TM compared to CONV and ICM plots with polyethylene mulch.
As an agroecosystem makes the transition from conventional to organic practices, changes in the pest management tactics used are often apparent. Despite varying degrees of efficacy among tactics, the issue of whether or not numbers of insect and nematode pests and their damage will become more severe in an organic system depends on the specifics of the pests and crops involved. Although many conventional systems rely on reactive strategies to deal with pest problems, an alternative approach is to redesign systems so that plant health is maximized, regardless of pest numbers, although this approach takes planning and time. An abrupt transition from conventional to organic may be risky if pest numbers are high and alternative practices are not yet in place. Hybrid systems, involving decreasing levels of conventional tactics and increasing levels of organic tactics, may be needed before the transitional period begins, in order to bridge the gap and lessen the impact of crop losses during the transitional period. The design of cropping systems with minimal pest impact requires a much more extensive and specific knowledge base than needed for reactive strategies.
Angela R. Davis, Charles L. Webber III, Penelope Perkins-Veazie, Julie Collins and Vincent M. Russo
Cultural practices have been reported to affect quality and phytonutrient content of watermelon. Knowing which varieties perform best under various production systems, and how these systems affect quality, yield, and phytonutrient content, is imperative to ensure high quality and yield. There is limited information on how watermelon [Citrullus lanatus var. lanatus (Thunb.) Matsum. & Nakai] varieties perform when grown with organic practices. Production characteristics of six watermelon varieties from certified organic seed sources were compared under high-(black plastic and mechanical cultivation for weed control) and low-input (no-till) organic culture. The high-input method utilized black plastic mulch and mechanical cultivation for weed control. The low-input utilized no-till planting. `Triple Star' was the most productive seedless variety in terms of number of fruit and marketable yield when data were combined across locations. `Early Moonbeam' produced the largest number of fruit, and the smallest fruit, of the seeded varieties. `Allsweet', a seeded variety, had the best marketable yield due to its larger size. `Triple Star' had the best quality (lycopene and °Brix content) when data were combined across locations. Among the seeded varieties, `Allsweet' had the best quality at both locations; however, average lycopene content on a per-fruit basis under low input production was not significantly different when compared to `Sugar Baby'. High-input production methods almost doubled the number of fruit produced for all varieties, producing greater yields, and heavier average fruit weights, but lower °Brix and lycopene content compared to the low-input production method.
Edmund J. Ogbuchiekwe, Milton E. McGiffen Jr. and Mathieu Ngouajio
Economic analysis compared the returns of cropping systems and management practices for production of fall lettuce (Lactuca sativa L.) and spring cantaloupe (Cucumis melo) following summer cover crops. The cover crop treatments included: cowpea [Vigna unguiculata (L.) Walp.] incorporated into the soil in the fall, cowpea used as mulch in the fall, sorghum sudangrass [Sorghum bicolor (L.) Moench] incorporated into the soil in the fall, and a bare ground control. Lettuce and cantaloupe were managed using conventional, integrated, and organic practices. The effect of each cropping system and management practice on crop yield, cost of production and net return was determined. In 1999 and 2000, yield and net return were greatest for cantaloupe and lettuce when the cowpea cover crop was incorporated into the soil before planting. The effect of crop management practice varied with type of cover crop. When lettuce was planted into cowpea-incorporated treatment in 1999, conventional management had the highest cash return followed by integrated crop management. In 2000, organically-grown lettuce after cowpea incorporated had the highest net return followed by integrated crop management grown under cowpea incorporated treatments. In 1999 and 2000, integrated cantaloupe following cowpea-incorporated treatment had the highest yield and cash-return. A 20% price premium for organic produce increased the net returns for the organic-grown lettuce and cantaloupe. Organic lettuce following cowpea-incorporated treatments produced a high net of $2,516/ha in 1999 and $5,971/ha in 2000. The net returns due to 20% organic premium price varied between 1999 and 2000 in cantaloupe production. They were highest for organic cantaloupe after bareground with a net return of $4,395 in 1999 and $3,148 in 2000 for organic cantaloupe after sudangrass.
V.M. Russo and Merritt Taylor
Many producers who have used conventional production methods for vegetables, and who want to convert to organic production, will have to pass through a 3-year transition period before their land can be qualified for organic certification. This transition can produce unique challenges. Use of several amendments has received interest for inclusion in organic production. How these affect vegetable production during the transition period was examined. Land was taken from perennial pasture and converted to production of the vegetables: bell pepper (Capsicum annuum L.), cv. Jupiter; processing cucumber (Cucumis sativus L.), cv. Earli Pik; and sweet corn (Zea mays L.), cv. Incredible (se endosperm genotype) using organic materials and methods with comparison made to production using conventional methods. Conventional and transition to organic portions of the field were separated by 25 m with the buffer zone planted with the same sweet corn cultivar used in the experimental plots and minimally maintained by addition of organic fertilizer. To the organic portion of the field, three levels of humates (0, 112, and 224 kg·ha–1) and three levels of corn gluten meal (0, 448, and 896 kg·ha–1) were applied in nine combinations. Yields for all crops were determined for all years. In the first year, bell pepper yields for plants under conventional production were higher than for the plants in the transition plots. In the remaining 2 years, bell pepper yields were similar under the two production systems. In the first 2 years, cucumber yields for plants under conventional production were higher than for the plants under transition to organic production. In the last year, cucumber yields were similar under the two production systems. In all years, sweet corn yields for plants under conventional production were higher than for plants under transition to organic production. Humates and corn gluten meal did not benefit yields of crops. An economic analysis comparing yields, prices, and costs of production of the crops under conventional and the transition to organic indicated that conventional practices generally provided more net revenue than did transition to organic production. Net revenue for the three species under the transition to organic for the 3 years was $2749 for three hectares. Net revenue for the three crops under conventional production for 3 years was $61,821, a difference of $59,072. Costs, yield, and prices will have to be considered when decisions are made concerning the adoption of organic practices.
Ariana P. Torres and Maria I. Marshall
., 2008 ). Moreover, Sierra et al. (2008) cited personal issues as key constraints to maintaining certification among decertified farmers who kept using organic practices. Family and labor health were the top two personal issues that motivated