What is in this article?:
- Much of California's water supply is polluted with nitrates. One of the sources of this pollution is farming.
- Nitrogen not utilized by plant eventually reaches water table.
- California is in the throes of creating a massive regulatory system that will mandate each farm adopt a fertilizer management plan.
Much of California's water supply is polluted with nitrates. One of the sources of this pollution is farming. California is in the throes of creating a massive regulatory system that will mandate each farm adopt a fertilizer management plan.
For soil sampling, Backman recommends:
- Soil probe or shovel; however, backhoe, soil auger or posthole digger may be used.
- Clean moisture-proof quart-size bags. Use paper bags only if soil is very dry.
- Clean plastic bucket to mix samples, optional.
- Samples collected for microbiology, nematode and pesticide residue analysis generally need refrigeration, so have a cooler and coolant available.
- Walk a zigzag course around or through the sampling area taking 20 to 30 cores, enough to make a quart of soil. Stay away from field edges.
— For furrow or field crops, take soil 12 inches below the surface or to the plowing depth.
— For tree and vine crops, soil samples should be taken one-foot increments to the depth of rooting which may require three to five samples from the same area.
- Collect one quart of soil and put in a clean quart-size bag.
- If collecting soils from multiple sites, composite by mixing in clean plastic bucket and taking one quart per sample.
- Clearly print on each bag using an indelible marker or ballpoint pen your name/company, site and sample description.
— Complete work request form. Print clearly and return it with your sample.
Backman prefers a tissue sample on permanent crops. With sufficient information, professionals like Backman can provide nutrient application recommendations. Picking fertilizer is important in system used, he added.
He said “80 percent” of the nutrient problems he encounters are water related. Nitrogen is very mobile in water and how and when a crop is irrigated has a lot to do with where nitrogen ends up.
Weather also plays a key role in when a crop is irrigated and its response to N. In a wet spring year a grape growers may wait until June to irrigate; in a dry year, it may be April when the first irrigation is applied. If a vineyard is irrigated too early in a wet year, N will move below the root zone.
Nitrogen management should focus on a quick, uniform bud break in grapes with slow foliage growth through the growing season with enough N to finish the season, promoting sugar and color. There should be enough N in the vines going into dormancy to promote strong spring growth the following year.
Backman encouraged growers to utilize crop consultants to monitor plants and keep good year-to-year records, taking tissue samples at specific points within a season.
“You cannot step into a river twice. Agriculture is always changing,” he said.
Be “proactive” in improving yield and quality while managing the environment above and below the ground, he concluded.