August 21, 2013

Nutrient Management Discussed At Seminar

By Patrick Cavanaugh, Editor

Terry Stark

At a CAPCA Ed Seminar in Exeter, California, with more than 75 Pest Control Advisors (PCAs)/Certified Crop Advisors (CCAs), the audience heard the latest on the efficient use of nitrogen, phosphorus and potassium fertilizers.

Terry Stark, CAPCA CEO/President, noted that CAPCA runs the CCA programs and about 95 percent of all CCAs are also California PCAs. CCAs will be important in the new mandates of managing nitrogen in farming.

Cory Schurman, with Agro-Culture Liquid Fertilizer, spoke about nitrogen efficiency. It all starts with the 4 R’s:

Attendees at CAPCA eds Exeter Nutrient Management Seminar

·      Right Source

·      Right Rate

·      Right Timing, and

·      Right Placement

“When N containing materials are applied to soils, certain generalized reactions take place that influence the relative availability of the N for crop uptake,” said Schurman.

Cory Schurman

Mineralizationis the process of transforming N from organic forms to inorganic N in soil. This occurs in a number of steps. Organic matter decomposes by breaking down complex organic molecules to smaller and more soluble inorganic ones such as ammonium and nitrate. Schurman noted that most soil microbes carry out mineralization. “The ideal conditions are soils with oxygen content greater than five percent, temperatures between 85 and 100 F, soil pH near 7.0, and moisture content near the soil’s holding capacity,” said Schurman.

Nitrificationis the reaction that creates nitrate from ammonium. Microorganisms carry out these reactions by meeting their energy needs, thereby oxidizing ammonium. The ideal conditions for rapid nitrification are temperatures at 75-85 F, well-aerated soils, pH between 6-8, soils with good water and nutrient levels and soils containing organic matter with good fertility.

Immobilizationoccurs when soil microbes assimilate plant-available N into their bodies or cells. “This most typically happens when a large amount of crop residue with a high C: N ratio is mixed with the soil. Soil N that is immobilized is not lost from the soil; rather, it is retained by the bacterial and humus until it slowly reverts to plant-available N through mineralization,” Schurman said.

Schurman emphasized it is critical that growers meet a crop’s nutrient demand curve.

·      Match the timing of the treatment with the crop’s ability to utilize the applied nutrient

·      Match the amount that is applied with the crop’s ability to make use of the treatment

·      Choose the balance and nutrient that offer the greatest opportunity for uptake.

·      Consider foliar feeding to meet a crop’s heavy nutrient needs.

To maximize yield potential, Schurman noted four additional points:

·      Complete soil/tissue analysis.

·      Consider crop potential.

·      Research limiting factors, with soil characteristics and nutrient availability in mind.

·      Design nutrient program.

Mark Davis, with Great Salt Lake Minerals, spoke about the role of Potash (K) in nutrient management.

Mark Davis

Davis focused on many crops regarding their potassium need. In vegetables, adequate K is required for both yield and quality. “Where K is limited, tomatoes, potatoes and cabbage often show discoloration of the internal tissue,” Davis said. “Both tomatoes and potatoes respond well to applied K in terms of total yield and percent of that yield meeting strict market standards.”

Adequate nitrogen is needed as N and K interact to help achieve maximum economic yield.

In tree crops, low K saw a 27 percent increase in spur mortality. This was attributed to a return bloom of 30 percent lower in low K trees, which led to a reduced yield. K removal from the soil is high in most permanent crops.

“Factors that affect K’s utilization include poor soil aeration, soil moisture that is too dry or too wet, soil temps that are too low and soil texture such as high clay content that holds onto K,” Davis said.

Davis noted that the K application must precede the uptake. “Understanding the major demands of K during the growth stage of the plant is important,” Davis said. “And make sure that K is available during this uptake.”

In determining the right rate of K, Davis noted that growers should start with a yield goal. “They should then determine crop need and potential removal of K. Growers should utilize soil and tissue sampling to determine soil K supply and mineralogy/moisture issues that may affect K availability.

Dan Munk

Dan Munk, UC Cooperative Extension Farm Advisor Fresno County, also spoke at the half-day event. Munk said that he has been the cotton farm advisor during his work in Fresno, but since cotton acreage is down, he has picked up the responsibility of irrigation and water management.

Munk spoke about many different nutrients along with important nutrient issues.

“You have start with the economics of crop productivity in that fertilizers/amendments have a cost,” Munk said. “There are also application costs and excessive vigor on permanent crops which increases cost of pruning. Excessive vigor can also impact insect and disease management.”

“And very importantly, growers need to understand the balance of fertilizer needs, according to each crop,” Munk said.

“Growers should also keep in mind environmental degradation in areas leading to water quality problems and greenhouse gas emissions,” Munk added.

Munk outlined effective fertilization practices in orchards, which include:

·      Fertigation.

·      Split Applications.

·      Accounting for nitrates in the irrigation water.

·      Planting legume cover crops.

·      Quickly incorporating or irrigating after a broadcast application.

·      Avoiding applications during the late fall and winter when uptake is minimal.

He also noted that foliar sprays of urea in the fall to help drop leaves could contribute to the total nitrogen needs of some orchard crops. Furthermore, in selecting a fertilizer material, consider the potential effects of other nutrients in the blend and the effect on soil pH.

Munk also noted situations where limited fertilizer applications may be warranted.

·      High rates of manure or compost were recently applied.

·      Legume cover crops were used.

·      Previous crop was not harvested.

·      Irrigation water is high in nitrates.

·      Crop has very low nutrient requirements, such as in young trees.

·      Some areas of the field may have low productivity zones.

Dr. Rob Mikkelsen, Western North America Director, International Plant Nutrition Institute (IPNI) spoke about soil, water and tissue testing for nutrient management.

IPNI is a global not-for-profit scientific and research education group on fertilizers.

Dr. Rob Mikkelsen

“You have all heard about nutrient management plans that will affect many growers throughout the San Joaquin Valley Water Quality Coalition. Water quality is what is driving all of this,” Mikkelsen said. The East San Joaquin area of Modesto, Turlock, Merced, and Madera, have those regulations in place and will begin January 2014. Growers in the coalition area must manage their nitrogen, with budgets. The regional water board is targeting the southern San Joaquin Valley next.

“The bottom line is if growers in the East San Joaquin Water Quality Coalition are in a zone that is vulnerable to nitrate leaching, they will each need a Certified Crop Advisor (CCA) to sign on his/her farm’s nitrogen management plans. The grower then submits it to the coalition.

“If every pound of nitrogen that we apply ended up in a plant, it would be easy; but, we would be lucky if we were to get half that N in the plant,” Mikkelsen remarked.

“In reality we are trying to balance all these inputs, the water, nitrogen fixation, organic matter, extra fertilizer, and manures, with what the plant needs. But some of nitrogen is harvested off, some goes back into the organic matter, some is lost as a gas, and some gets leached. So we are trying to predict these things while guessing what the weather will be like, and it’s very difficult,” Mikkelsen said. “And if you mess up on one or two of these things, the whole process is out of balance.”

“So what we are being asked to do is a real challenge. But I think all of us can make some adjustments to do a better job,” he said. “The 4 R’s are a good way to approach the N applications, and have that discussion with regulators. If you can describe the source, rate, time and place, you are doing something right and showing some accountability of the decisions that you are making.”

“We will all need to show why we are doing what we are doing and how we are minimizing those losses into the water. If we cut back on N use but put it on at the wrong time, then we are not doing the right thing. We all need to be mindful of the right amount at the right time,” Mikkelsen said. “We need to do this because we have nitrates in the ground water in many parts of the state. And some are saying that we are paying for the sins of our grandfathers and that may be true, but we are the ones that need to change things to make some improvements and clean it up.”

According to UC Davis studies, high economic yields are compatible with a minimal amount of leaching. The research never showed leaching at zero, but it worsens as growers push yields. “More is not always good,” Mikkelsen said.

Also speaking at the seminar was Dennis Keller, Sub-Watershed Coordinator, Kaweah Sub-Watershed  Kings County Conservation District. His topic was the Irrigated Lands Regulatory Program and Nitrogen.

Following lunch,  Dr. Eric Ellison, with Agrium spoke about: “It Takes More than NPK”; Dr. Steve Petrie, Yara North American spoke about calcium’s role in nutrient management; and Bill Green, Center for Irrigation Technology, California State University Fresno spoke about fertigation and nutrient management. We will cover what these speakers said at a later time on this blog.