An understanding of nitrogen (N) uptake and the partitioning of N during the season by the carrot crop (Daucus carota subsp. sativus [Hoffm.] Arkang.) is required to develop more efficient N fertilization practices. Experiments were conducted on both organic and mineral soils to track the accumulation of dry matter (DM) and N over the growing season and to develop an N budget of the crop. Treatments included two carrot cultivars (`Idaho' and `Fontana') and 5 N rates ranging from 0% to 200% of the provincial recommendations in Ontario. Foliage and root samples were collected biweekly from selected treatments during the growing season and assessed for total N concentration. Harvest samples were used to calculate N uptake, N in debris, and net N removal values. Accumulation of DM and N in the roots was low until 50 to 60 days after seeding (DAS) and then increased linearly until harvest for all 3 years regardless of the soil type, cultivar, and N rate. Foliage dry weight and N accumulation were more significant by 50 to 60 DAS, increased linearly between 50 and 100 DAS, and reached a maximum or declined slightly beyond 100 DAS in most cases. The N application rates required to maximize yield on mineral soil resulted in a net loss of N from the system, except when sufficient N was available from the soil to produce optimal yield. On organic soil, a net removal of N occurred at all N application rates in all years. Carrots could be used as an N catch crop to reduce N losses in a vegetable rotation in conditions of high soil residual N, thereby improving the N use efficiency (NUE) of the crop rotation.
Sean M. Westerveld, Alan W. McKeown and Mary Ruth McDonald
Laura Avila, Johannes Scholberg, Lincoln Zotarelli and Robert McSorely
Poor water- and nutrient-holding capacity of sandy soils, combined with intense leaching rainfall events, may result in excessive N-fertilizers losses from vegetable production systems. Three cover cropping (CC) systems were used to assess supplemental N-fertilizer requirements for optimal yields of selected vegetable crops. Fertilizer N-rates were 0, 67, 133, 200, and 267; 0, 131, and 196; and 0, 84, 126,168, and 210 kg N/h for sweet corn (Zea mays var. rugosa), broccoli (Brassica oleracea), and watermelon (Citrullus lanatus), respectively. Crop rotations consisted of sunn hemp (Crotalaria juncea) in Fall 2003 followed by hairy vetch (Vicia villosa), and rye (Secale cereale) intercrop or a fallow. During Spring 2004, all plots were planted with sweet corn, followed by either cowpea (Vigna unguiculata) or pearl millet (Pennisetum glaucum), which preceded a winter broccoli crop. Hairy vetch and rye mix benefited from residual N from a previous SH crop. This cropping system provided a 5.4 Mg/ha yield increment for sweet corn receiving 67 kg N/ha compared to the conventional system. For the 133 N-rate, CC-based systems produced similar yields compared to conventional systems amended with 200 kg N/ha. Pearl millet accumulated 8.8 Mg/ha—but only 69 kg N/ha—and potential yields with this system were 16% lower compared to cowpea system. For a subsequent watermelon crop, trends were reversed, possibly due to a delay in mineralization for pearl millet. Because of its persistent growth after mowing, hairy vetch hampered initial growth and shading also delayed fruit development. Although CC may accumulate up to 131 kg N/ha actual N benefits, N-fertilizer benefits were only 67 kg N/ha, which may be related to a lack of synchronization between N release and actual crop demand.
Plants provide humans with food, fiber, feed, ornamentals, industrial products, medicine, shelter, and fuel. As vegetation, they maintain global environmental integrity and the carrying capacity for all life. From an anthropocentric perspective, plants serve as genetic resources (PGR) for sustaining the growing human population. Research on PGR can provide basic knowledge for crop improvement or environmental management that enables renewable, sustainable production of the preceding necessities. PGR also provide the raw material for increasing yield and end product's quality, while requiring fewer inputs (water, nutrients, agrichemicals, etc.). The staples of life—30 or so major grain, oilseed, fiber, and timber species—comprise the “thin green line” vital to human survival, either directly, or through trade and income generation. Many crop genebanks worldwide focus on conserving germplasm of these staples as a shield against genetic vulnerability that may endanger economies and humanity on an international scale. Fewer genebanks and crop improvement programs conserve and develop “minor crops,” so called because of their lesser economic value or restricted cultivation globally. Yet, these minor crops, many categorized as horticultural, may be key to human carrying capacity—especially in geographically or economically marginal zones. The USDA/ARS National Plant Germplasm System (NPGS) contains a great number and diversity of minor crop germplasm. The NPGS, other genebanks, and minor crop breeding programs scattered throughout the world, help safeguard human global carrying capacity by providing the raw genetic material and genetic improvement infrastructure requisite for producing superior minor crops. The latter may represent the best hope for developing new varieties and crops, new crop rotations, and new renewable products that in the future may enhance producer profitability or even ensure producer and consumer survival.
Kathleen Delate and Vincent Lawson
Organic farming has increased to a $6 billion industry in the U.S. and continues to expand 20% annually. In Iowa, organic acreage for all crops has increased from 13,000 in 1995 to 130,000 in 1999. Most organic farmers rely on crop rotations, compost, or manure applications, and cover crops to maintain soil fertility. In our trials at the Iowa State Univ. Muscatine Island Research Farm, a cover crop of hairy vetch (Vicia villosa) and rye was seeded in the fall and incorporated 2 weeks prior to transplanting `Lantern' pepper plants. Other organic and conventional soil treatments were applied at transplanting and at 3 weeks post-planting. Four replications of 40 peppers transplanted at 31 × 61-cm spacing under seven fertilization treatments were observed for plant growth and yields. The fertilization goal was to obtain equivalent nitrogen and calcium rates in the organic and conventional systems. Plants fertilized with the compost at 88 kg/ha N plus BioCal® (a liming industry by-product) were not significantly greater in leaf biomass than plants conventionally fertilized with equal amounts of N. All organic and conventional treatments had greater biomass and yield than the organic and conventional controls (no fertilizer), respectively (P = 0.05). Pepper fresh weight was greater in the vetch-strips treatment than in the vetch-incorporated, and the 44 kg/ha N compost treatment, but significantly less than the conventionally fertilized plants. Second year results demonstrated similar results to the 1998 trial where the greatest yields in the organic system occurred in the compost at 88 kg/ha N plus BioCal® treatment, demonstrating to organic farmers that comparable yields can be obtained in systems employing alternatives to synthetic nitrogen fertilizer.
N.G. Creamer, K.R. Baldwin and F.J. Louws
Consumer demand for organically produced food and the desire by many farmers to eliminate chemical fertilizers and pesticides is increasing the need for research and educational programs to support organic farmers. To date, the land-grant universities and the cooperative extension service have been viewed by organic farmers as unresponsive to this need. The primary reason for the unresponsiveness has been inadequate training and resource materials available to extension agents. In 1998, we conducted an intensive training for agriculture agents in North Carolina. Funding was provided by the USDA SARE Professional Development Program. More than 50 agents participated in a series of workshops that were offered together as a graduate course worth four NCSU credits. Much of the training was conducted on the Organic Unit at The Center for Environmental Farming Systems (CEFS), a 100-acre facility dedicated to research and education in organic farming systems. The hands-on training consisted of lectures, demonstrations, field trips, and class exercises. The topic areas included soil biology/ecology; crop rotation; organic nutrient management; composting; cover crop management; organic weed, insect, and disease management; appropriate tillage practices; organic greenhouse management; marketing organic produce; integrating animals into organic crop production systems; delivery systems for disseminating information to organic producers, and; social and community development aspects of sustainable agriculture. Unique features of the workshops were the interdisciplinary approach to teaching them, and the integration of information about interactions between production factors. The training was very well-received and will serve as a model for future extension programming. A training manual, slide sets, extension publications, and a Web site are being created to further support agents as they conduct programming in their own counties.
Annette Wszelaki, Sally Miller, Douglas Doohan, Karen Amisi, Brian McSpadden-Gardener and Matthew Kleinhenz
The influence of organic soil amendments (unamended control, composted dairy manure, or raw dairy manure) and weed treatments [critical period (CP) or no seed threshold (NST)] on diseases, growth parameters, yield, and postharvest quality was evaluated over 3 years in a transitional organic crop rotation of tomato, cabbage, clover, and wheat. More growth, yield, and postharvest quality parameters were affected by amendment treatments in cabbage than in tomato. Significant differences in yield among amendment treatments were found in 2001 and 2003 in cabbage, with higher marketable and total yields in amended vs. control plots. Soil management effects on cabbage varied annually, though amendments were required to maximize crop growth, as head weight, size, and volume and core volume of treatment plots exceeded the control plots in 2002 and 2003. Few differences were found between weed treatments, although in 2001 cabbage heads from the NST treatment were larger than heads from the CP treatment. Similar results were found in tomato in 2003. Also, the CP treatment had a higher Area Under the Disease Progress Curve than the NST treatment in tomato in 2003. Overall, disease pressure was highest in tomato in 2001. But disease levels within years were mostly unaffected by amendment treatments. In cabbage, disease was more common in 2002 than in 2003, although head rot was more prevalent in compost-amended plots in 2003 than in manure-amended or control plots. Tomato postharvest quality parameters were similar among amendment and weed treatments within each year. Soil amendment may enhance crop yield and quality in a transitional-organic system. Also, weed management strategy can alter weed populations and perhaps disease levels.
Matthew D. Kleinhenz, Sonia Walker, John Cardina, Marvin Batte, Parwinder Grewal, Brian McSpadden-Gardener, Sally Miller and Deborah Stinner
The risk: reward for a transition to organic vegetable farming near urban areas and changes in soil, crop, and economic parameters during transition are poorly understood. A 4-year study was initiated in 2003 at the Ohio State Univ.–OARDC to document the relative advantages of four transition strategies and their effects on major cropping system variables. Soil previously in a vegetable-agronomic crop rotation has been maintained fallow, planted to a mixed-species hay, used in open field vegetable production, or used in vegetable production under high tunnels, transition strategies with a range of management intensity and expected financial return. Each strategy was replicated four times within the overall experimental area. Half of the soil in each strategy unit was amended with composted dairy manure while the remaining soil was unamended. Field vegetable plots have been planted to potato, butternut squash, and green bean. High tunnels have been planted to potato, zucchini, and a fall–spring rotation of beet, swiss chard, mixed lettuce, radish, and spinach. Data describing the outcomes of the strategies in terms of farm economics, crop yield and quality, weed ecology, plant pest and disease levels, and soil characteristics (physical, chemical, biological) have been recorded. Inputs in the high tunnels have exceeded inputs in all other strategies; however, high tunnel production has widened planting and harvesting windows and increased potato yield, relative to open field production. To date, compost application has increased crop yield 30% to 230% and influenced crop quality, based on analytical and human panelist measures. Weed (emerged seedlings, seedbank) and nematode populations also continue to vary among the transition strategies.
Warren Roberts, Wayne Fish, Benny Bruton, Tom Popham and Merritt Taylor
Grafted cucurbits are commonly grown in various Asian and European countries, but only rarely in North America. Disease control in fields where crop rotation cannot be practiced is a common justification for grafting cucurbits. In the present study, grafting is being examined as a methyl bromide alternative, which may allow cucurbits to be grown in fields where heavy disease pressure would make production of nongrafted cultivars impractical. A study with watermelons (Citrullus lanatus) grafted onto rootstocks of squash and gourd was conducted at Lane, Oklahoma in 2004. Treatments consisted of watermelon cultivars SF 800, SS 5244, SS 7167, SS 7177, and SS 7187 from Abbot & Cobb Seed Co., grown on their own roots, or grafted onto rootstocks of RS1330, RS1332, RS1420, or RS 1421. Controls consisted of nongrafted cultivars Sangria, Royal Sweet, Jubilee, and Jamboree. Two fields were planted, with three replications per field. Plants were grown on 1 m centers, with rows 3 m apart. Yields of grafted plants were generally equal to or greater than the nongrafted plants. Sugar content, measured as soluble solids, was affected minimally, if any, by grafting. Lycopene content of fruit from grafted plants was equal to, or marginally better than, fruit from nongrafted plants. Fruit firmness, as measured by a penetrometer, was significantly greater in the grafted fruit than in the nongrafted fruit. The firmest fruit occurred with SS 7167 scions, grafted onto RS 1420 rootstock, which had a value of about 2.0 × 105 Pascals. The nongrafted plants had values of about 1.0 × 105 Pascals, or less. Matching of scions with appropriate rootstocks was important, as interactions did occur. Certain combinations were significantly superior to other combinations. We estimate that the cost to purchase a grafted seedling plant from a seedling supplier would be $0.75 to $1.00, which would include the cost of the seed and the grafting operation. This cost would compare favorably with the cost of applying methyl bromide to the soil and then planting nongrafted seeds or transplants. Higher plant survival due to disease resistance along with planting fewer plants per hectare is anticipated with grafted plants. The high values in fruit firmness in grafted fruit should be of particular interest to the fresh-cut industry.
George E. Boyhan, Julia W. Gaskin, Elizabeth L. Little, Esendugue G. Fonsah and Suzanne P. Stone
in northeast Georgia indicate demand exceeds supply. Growers themselves have identified the need for better production information and the need for research-based information on crop rotations adapted to regional growing conditions. Organic farms in
Duane W. Greene
are advanced. Among those included are cultivar selection, field selection, field preparation, crop rotation, soil solarization, pruning, polyethylene mulch irrigation, salinity management, and fertilization. A substantial portion of the book is