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Title: SUMMER COVER CROPS AND REDUCED IRRIGATION RATES ENHANCE TOMATO YIELDS AND GRADES IN SOUTH FLORIDA

Author
item WANG, QINGREN - U FL HOMESTEAD
item KLASSEN, WALDEMAR - U FL HOMESTEAD
item BRYAN, HERBERT - U FL HOMESTEAD
item LI, YANCONG - U FL HOMESTEAD
item CODALLO, MERLYN - U FL HOMESTEAD
item Abdul Baki, Aref

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2005
Publication Date: N/A
Citation: N/A

Interpretive Summary: This manuscript describes a biologically-based production system for growing fresh-market tomatoes in winter in Florida. It uses four nematode-resistant cover crops (sunn hemp, velvetbean, cowpea, and sorghum sudangrass) and the nematode-resistant tomato variety - Sanibel. The cover crops are planted in summer, flail-mowed in October, and incorporated in to the soil before transplanting the tomatoes. Total marketable yields and extra-large fruit yields in the methyl bromide alternative system are equal or higher than the average yields produced in Florida using the conventional system that requires fumigating the soil with methyl bromide. The alternative production system offers many advantages including eliminating the need for methyl bromide or any other soil fumigant. The cover crops fix nitrogen and reduce the input from commercial fertilizers. They further add organic matter to the soil. The alternative system is suggested for soils where the nematode population is low to moderate. Eliminating methyl bromide, reducing nitrogen input from fertilizers, and optimizing irrigation, reduce production cost, conserve natural resources, and protect the environment. Users of this research are vegetable and fruit growers, environmentalists, extension specialists, and the American public.

Technical Abstract: : A two-year experiment was conducted at Homestead, Florida, to evaluate use of nematode-resistant cover crops as biological alternatives to methyl bromide (MeBr) in growing a subsequent crop of fresh-market tomatoes (Lycopersicon esculentum, Mill.), and to determine irrigation rates that would increase tomato yields. The cover crops were cowpea (Vigna unguiculata L., cv. Iron Clay), velvetbean (Mucuna deeringiana), sunn hemp (Crotalaria juncea L. cv. Tropic Sun), and sorghum sudangrass (Sorghum bicolor × S. bicolor var. Sudanese. A weed-free fallow served as a control. The cover crop residues were planted in summer and incorporated into the soil in the fall. The cover crops were followed with 'Sanibel', a nematode-resistant tomato cultivar in 2001 and 2002. The beds were irrigated manually by activating valves when the tensiometer readings reached -5, -10, -20 and -30 kPa. The cover crops produced from 3.6 to 12.5 t?ha-1 of dry biomass with nitrogen (N) content of 35 - 356 kg?ha-1 each year. The lowest N contribution was from sorghum sudangrass and the highest from sunn hemp. Harvested fruit was graded following Florida Tomato Committee Standards. Based on the two-year data, tomato marketable yields were increased from 5.3 to 14.3% by the cover crops, and the greatest increases occurred in the sunn hemp followed by the cowpea treatments. Reducing irrigation to -10, -20, and -30 kPa significantly improved marketable yields by 16, 21 and 29%, respectively, over the yield at the commonly applied -5 kPa. Moreover, irrigation based on -30 kPa used 70% less water than at -5 kPa. The yields of extra-large fruit in the sunn hemp and cowpea treatments averaged 28 t?ha-1, and were significantly higher than yield in the fallow treatment. Likewise, yields of extra-large fruit were 23, 26, 28 and 29 t?ha-1 at irrigation rates of -5 -10, -20 and -30 kPa, respectively.