What is in this article?:
- California agriculture in groundwater controversy over nitrate contamination.
- Dairy, almonds and citrus growers are taking steps to cut down on unnecessary nitrogen use and improved efficiency in irrigation delivery systems for nitrogen and other nutrients.
Less is more
Using too much nitrogen is a detriment, he said, producing fruit that is too large and less marketable: “There is no incentive as a grower to over-fertilize.”
Brown recommends soil samples at least every three years. He said differing varieties require different adjustments in fertilization, and said it’s important to “pinpoint physiological stages when a tree is mostly likely to pick up (the nutrients).”
A third of the fertilizer used in his operation is foliar. “We want to get nitrogen into the tree, not the ground and not the groundwater,” he said.
• Stuart Pettygrove, UC soils specialist, was among those who talked of the lack of uniformity in application of nitrogen using furrow or border irrigation.
He recommends using soil nitrate and plant tissue testing in forage systems. And he would like to see conversion of manure sludge and solids to organic fertilizers usable on a wider range of crops.
• Larry Schwankl, UC irrigation specialist, said one way of avoiding the lack of uniformity in furrow or border irrigation is to reduce the length of the field.
“Nobody wants to farm an eighth mile long field,” he said. But cutting back from a half mile to a quarter can mean more uniformity in irrigation and flow of nutrients. With micro irrigation, Schwankl said, “deep percolation losses can be minimized.”
• Growers need to establish realistic yield goals, said Bob Hutmacher, UC Extension specialist and director of the West Side Research and Extension Center.
“In cotton, you cannot expect a 5-bale yield (per acre) every year,” he said.
Under typical winter rainfall and temperature conditions, he said, most nitrogen in fertilizer applied in ammonia forms would be converted to nitrate by planting time in the spring. That’s one of the reasons why fall or early winter applications are not recommended for a late winter or early spring planted crop.
Crop rotations matter. Hutmacher said rotations likely to produce higher soil nitrogen include cotton in rotation with shallow-rooted vegetable crops; garlic, processing tomatoes or field corn; and the first year after alfalfa.
Rotations likely to produce lower soil nitrogen include cotton in rotation with several prior years of cotton, small grains, safflower and sugar beets.
Hutmacher said anhydrous ammonia is slow to covert to nitrate in the soil.
Some stabilization products are being used outside California and could be beneficial, Hutmacher said.