Quality Continued from Page 15
broccoli, Brussels sprouts, cabbage, cauliflower, celery, lettuce, peppers, spinach and tomatoes. It is available at cropmanage.ucanr.edu. CropManage can be used to calculate irrigation recommendations inminutes or inches, and nitrogen fertilizer in ei- ther pounds or gallons. Salinas Valley growers already use the program 2,000 times a month to help make manage- ment decisions. In one recent study in a commer-
cial Sal inas Val ley romaine lettuce f i e ld, UCCE researchers used the CropManage recommendat ions to reduce nitrogen applications by 62 pounds an acre compared to the farm- er’s practice, and still increased the yield by nearly 1,500 pounds. The research behind CropManage shows that spoon-feeding nitrogen to the cropduring the course of the growing season is the most effective way to mini- mize nitrate leaching.
“If you’re making large fertilizer ap- plications early in the crop cycle, that nitrogen will be very subject to leach- ing,” Cahn said. “You’re going to have to account for all the sources of nitrogen, including residual nitrate in the soil and water from high-nitrate wells. The soil quick test will also allow you tomake ad- justments in your fertilizer applications.” Even using CropManage, the soi l quick test, crop rotat ion and other strategies, Central Coast vegetable growers could face nutrient-manage- ment challenges. One of the questions about the regu- lations is that nitrate-nitrogen in water used to germinate and start the crop wouldbe counted, even if the plantswere too small to take upmost of the water. Another issue is that the nitrogen in compost would be counted as equiva- lent to synthetic fertilizer, which might discourage use of compost to build healthy soil that sequesters both car- bon and significant amounts of nitro- gen. The water quality agency’s own records suggest the regulations may ignore potential for significantly re- ducing nitrate leaching by rotating to deeper-rooted crops. The regional board has been receiving information from farmers on nitrogen applications the last six years as part of Ag Order 3.0, and those reports show a wide range of fertilizer practices, both among growers and depending on the crop. In 2017, Central Coast farmers sub- mitted nitrogen reports for 1,472 lettuce ranches and for 821 broccoli fields. The reports show the difference in these crops’ nitrogen uptake, suggesting rota- tion could be one tool in keeping nitrates out of groundwater. “With broccoli, most growers were ap- plying less than the crop took up,” Smith said. “Broccoli is a deep-rooted crop that can scavenge for nitrogen.” ( Bo b J o hn s o n i s a r e p o r t e r i n Sacramento. He may be contacted at bjohn11135@gmail.com.)
advisor. “We think it will be valuable in meeting the new requirements. We let a computer do the calculations for specific fields. It also lets you keep field-specific records, and you can export the records for regulatory requirements.” Cahn has been the lead researcher in developing CropManage, which can be used to help make management de- cisions for vegetable crops including
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16 Ag Alert December 16, 2020
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