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- Author or Editor: Nancy Roe x
Utilization of municipal waste composts on vegetable crops may be advantageous if research can determine appropriate product maturity and quality standards, application methods and rates, application timing, and supplemental nutrient requirements. Experiments using compost for seed germination and seedling growth indicate that mixtures of compost with amendments such as perlite and vermiculite result in acceptable growth rates, but often require additional N and K for optimum growth. In the field, compost generally improves soil characteristics for vegetable crop growth. Tests using compost rates from 12 to 336 t·ha–1 either increased or did not change yields of vegetable crops. Highest yields are often produced from a combination of composts with additional nutrient sources. When the composts were used as mulches, vegetable crop growth and production were generally higher than from plants in unmulched plots, but lower than those from plots with polyethylene mulches. If growers are to accept the use of composts, the compost must be a consistent product, and yield increases must be high enough to justify the costs of transporting and applying the compost.
In many areas, dairies and other concentrated animal operations must modify their waste handling systems. Utilization of locally produced manures by vegetable production operations may increase crop yields while preventing discharge of potentially polluting nutrients into waterways. Composting is often recommended to stabilize nutrients, lower the volume of manure, and produce a product that may control some plant diseases. However, composting has costs in time and equipment, so some growers prefer using uncomposted manure. Dairy manure compost at 22 (LC), 45 (MC), or 90 (HC) t·ha–1 or dairy lot scrapings at 45 t·ha–1 (FM) were tilled into soil before seeding a dryland cantaloupe (Cucumis melo L.) crop. All plots, including an unamended control (UC), were fertilized with a total of 23N–14P–0K (kg·ha–1). After removal of the cantaloupe in late summer, drip irrigation was added, broccoli (Brassica oleracea var. botrytis Mill.) seedlings were transplanted into the identical plots, and 112N (kg·ha–1) was sidedressed. Cantaloupe yields from FM, LC, MC, HC, and UC plots were 5.4, 3.4, 2.1, 4.5, and 1.5 t·ha–1, respectively. Broccoli yields from FM, LC, MC, HC, and UC plots were 4.1, 3.6, 4.4, 4.1, and 2.2 t·ha–1, respectively. All rates of compost or manure increased yields of cantaloupe, and the subsequent broccoli crop. Use of the manure resulted in highest increase in potential net income from sales of cantaloupe and broccoli.
Rapid production of compost often results in crop damage by phytotoxic compounds or high C/N ratios in immature (uncured) compost. The influence of immature biosolids-yard trimmings compost on germination and growth of cucumber (Cucumis sativus L.) was evaluated. Germination percentages of cucumbers seeded in equal parts (v/v) of compost and vermiculite were similar to those in vermiculite. When screened compost was placed in flats and compared with flats of potting mix or sandy field soil, germination percentages were 98, 96, and 89 for mix, sand, and compost respectively. Germination in compost-amended field plots was higher than in soil when cucumbers were planted 1, 2 or 10 weeks after compost application, but similar in 3 and 5 week plantings. Use of this immature compost increased, decreased, or did not affect cucumber seed germination, depending on media and growing conditions.
The Atlantic hurricane season stretches from June to November, and the vegetable growing season in South Florida begins in August. This means that pre-plant, planting, and early harvesting operations are performed during hurricane season. Three major hurricanes striking our area during two consecutive growing seasons have helped to teach us how to give vegetable crops the best chance of survival. On a 4-ha farm growing diversified vegetable crops, there have been clear differences in crop survival. Tiny seedlings of most crops were generally killed by driving rains and strong winds. However, 7- to 10-cm-tall transplants in plastic cell trays survived surprisingly well when placed on the ground in an area that did not flood and was protected from flying debris. During the hurricane with the highest winds, large plants, such as tomatoes and squash, were defoliated. Even plants that survived defoliation and regrew were injured, so they were vulnerable to diseases later in the season. It actually appears to be best not to stake crops in extremely high winds. Staked and tied tomatoes often broke off at the top string. In winds of over 90 knots, unstaked eggplants fared best of any mature crops. They fell over immediately and, lying on the ground, were protected from the high winds. After the storm passed, they were pulled upright, staked and tied, and produced excellent yields. Sweet corn also fell over, but, over a period of a week, gradually returned to about a 45° angle where it produced about 30% of the normal yield. Of course, each hurricane has different characteristics; what works in one may not be the best during others. We are, however, hoping not to have a chance to learn more about how crops survive hurricanes.
Composts may improve crop growth in sandy soils. A biosolids-yard trimming compost (C) was incorporated into sandy soil at 134 t·ha–1 (49.7% moisture) before applying polyethylene mulch. Fertilizer (F) was applied at 0%, 50%, and 100% of the grower's rate (71N–39P–44K t·ha–1 broadcast and 283N–278K t·ha–1 banded in bed centers). `Elisa' pepper transplants were planted 20 Jan. 1994. Marketable fruit weights were 20, 31, and 32 t·ha–1 without C and 30, 35, and 32 t·ha–1 with C for 0%, 50%, and 100% F, respectively. Pepper fruit weights increased with increasing F rates and were higher in plots with C than without C. Without removing mulch, `Thunder' cucumbers were seeded on 26 Sept. 1994. Marketable fruit weights were similar at the three F levels, but were 23 and 27 t·ha–1 without and with C, respectively. One application of C significantly increased bell pepper yields and a subsequent cucumber crop.
Recently, an increasing number of restaurants in Palm Beach County, Florida, have been requesting squash (Cucurbita pepo) flowers from local vegetable growers. Typically, current field-grown squash cultivars produce a higher ratio of female to male flowers, with the emphasis on fruit production. However, a market for squash blossoms indicates a need for cultivars that produce higher numbers of consistently developing male flowers throughout the growing season. In order to evaluate male squash blossom production, 10 squash cultivars, including yellow-summer, zucchini, round, and scallop-types, and one compact-type pumpkin, were field-grown during the 2005–06 growing season. The average number of male flowers per plant by week was recorded for 7 weeks, starting when the first male flowers were identified within the entire trial. In addition to blossom counts, flower traits, such as bell height, depth, volume, and weight were also recorded. Preliminary results from the 2005 season indicate that the commercial yellow-summer squash cultivars, Mulitpik and Early Prolific Straightneck, and the zucchini cultivars, Jaguar and Raven, produced fewer male flowers on a week-by-week and total basis. The cultivar, White Bush Scallop, produced significantly more male flowers then any other entry, with an average of 9.8 male flowers per plant per week. Little or no difference was seen in bell height and depth among the 11 cultivars; however, two cultivars, Costa Romanesque and Hybrid Pam (compact pumpkin type) had significantly greater bell volumes and weights, indicating a much larger blossom size.
Increased dependency of conventional agriculture on inorganic fertilizers and fossil fuels may hamper long-term sustainability of agricultural production. Sunn hemp (Crotalaria juncea) was tested during summer in a Community Supported Agriculture vegetable crop operation located in Southeast Florida, from 2003 to 2005. Farm system components included sunn hemp (SH) vs. a conventional fallow during summer, tomato (Lycopersicon esculentus) and pepper (Capsicum annum) during winter and spring sweet corn (Zea mays). Tomato and pepper were fertilized with 0, 67, 133, 200 kg N/ha (2003) vs. 0,100, 200 kg N/ha (2004/05). Sweet corn received 133 or 200 kg N ha (2003) vs. 100 kg N/ha (2004/05). Average SH biomass was 3.7 Mg/ha. In 2003 tomato yields following SH without supplemental N were similar to fallow, with 200 kg N/ha. By the third year, tomato and pepper yields in SH plots were 25% and 26% higher, respectively. Conventional pepper amended with 200 kg N/ha had only 8% higher yields than treatments amended with 100 kg N ha and CC. Overall, sweet corn had low yields, but yields increased if the preceding tomato/pepper crop received higher N rates. In 2003, sweet corn fertilized with 200 kg N/ha following a SH-fall vegetable crop produced 17% higher marketable yields compared to the fallow treatment. During 2004 and 2005, sweet corn within the SH-non-fertilized tomato system produced 29% higher yields compared to a similar conventional system. Results show that, in this rotation, both fall vegetable crops and sweet corn yield benefit from residual N fertilizer. Mineralization of SH may thus not only benefit the immediately following crop, but its effects can be seen later during the year.
Some possible alternatives to soil fumigation with methyl bromide include soil solarization and the use of composts to modify soil microorganism populations. We tested combinations of solarization and compost on a broccoli (Brassica oleracea var. botrytis L.) crop on an organic farm. Treatments were: solarization with compost (SC); solarization without compost (SW); compost only (NC); and an untreated control (NW). Dairy manure compost was applied manually to compost plots at 22 Mg/ha, raised beds were constructed, and solarization plots were covered with clear polyethylene from 13 July to 26 Aug. Black polyethylene mulch was applied to all plots, covering the clear polyethylene. Broccoli, cv. Packman, transplants were planted into the beds and fertilized with fish emulsion fertilizer three times for a total of ≈22 kg/ha N. Broccoli heads were harvested on 1, 5, and 9 Dec., trimmed to 15 cm, weighed and counted. Marketable yields were 8704, 7117, 8169, and 8374 (kg/ha) and mean head weights were 353, 228, 286, 313 (g) for SC, SW, NC, and NW, respectively. Under these conditions, head weights were highest with compost and solarization, and marketable yields were similar.