Latest Findings on Crop Yields and Plant Health for Growing Processing Tomatoes

Processing tomatoes grown with 10 tons per acre of composted poultry manure achieved yields 9 to 22 percent above controls, according to new research funded by the California Tomato Research Institute and carried out by the University of California Cooperative Extension. Yield increases were most pronounced for soils with potassium levels below 200 ppm.

Investigation of Sustaining Tomato Plant Health and Yield with Composted Manure

Five sites were established in grower fields in Yolo County and treated with composted poultry manure at amounts from 5 to 20 tons per acre. Treatments varied from site to site but always included composted poultry manure at a minimum of 10 tons per acre mounded on the top of a pre-formed bed. A synthetic fertilizer blend mimicking the compost nutrients, as well as plots with potassium fertilizers, were also compared. The highest yields were achieved with the compost treatments, and yields correlated with compost application rates in four out of five sites. The synthetic blend and the potassium treatments also resulted in yield increases.

“When comparing composted poultry manure amongst trials with manufactured NPK (nitrogen-phosphorus-potassium) at rates that mimic those of compost, the composted manure was significantly better performing,” wrote the authors. “Composts were apparently providing a benefit beyond NPK.”

The Effect of Cover Crops, Compost, and Gypsum Amendments on Soil Structure and Disease in Processing Tomatoes

The study compared several different types of compost, including poultry manure, green/food material, and tomato cannery waste composts, alone and in combination with gypsum and cover crops. The study took place at UC Davis’ Russell Ranch test facility and at a nearby grower field. The highest yields at Russell Ranch occurred in plots fertilized with compost only. Cover-cropped plots had the lowest yields.

In the grower fields, the highest yields were associated with the northernmost section of the field, and compost application did not increase yields. In general, compost-treated plots had higher levels of sodium, phosphorus, and potassium in the soil; and the gypsum treatments resulted in higher levels of sulfate-sulfur. Cover-cropped areas had the lowest soil bulk density. Saturated hydraulic conductivity, the ability of water to move through the soil, was more favorable in the amended plots than in the control. Plots were inspected for damage from fusarium, verticillium, powdery mildew, spotted wilt, and nematodes, and compost-amended plots had the lowest damage overall.

“For the second year, beds amended with compost had less disease damage in the August observations before harvest compared to non-compost amended soils,” wrote the authors. “In light of the benefits of these amendments, it will be necessary to compare changes in yield, soil structure and disease with the cost of amending soils to decide whether the amendments would be economically beneficial to use.”
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