Nutrient Management Discussed
By Patrick Cavanaugh, Editor
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.
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.
with Agro-Culture Liquid Fertilizer, spoke about nitrogen efficiency. It all
starts with the 4 R’s:
· Right Source
|Attendees at CAPCA eds Exeter Nutrient Management Seminar|
“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.
is 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.
is 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.
occurs 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
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.
with Great Salt Lake Minerals, spoke about the role of Potash (K) in nutrient
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, 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:
· Accounting for nitrates in the irrigation water.
· Planting legume cover crops.
· Quickly incorporating or irrigating after a broadcast
· 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
· Some areas of the field may have low productivity
Dr. Rob Mikkelsen, Western North America Director, International Plant Nutrition
Institute (IPNI) spoke about soil, water and tissue testing for nutrient
IPNI is a global
not-for-profit scientific and research education group on fertilizers.
“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.
|Dr. Rob Mikkelsen|
“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
“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.
Labels: Bill Green, cal Ag today, CAPCA ED Seminar, Cory Schurman, Dan Munk, Dennis Keller, Eric Ellison. Steve Petrie, Mike Davis, Nitrogen, Nitrogen budgets, Rob Mikkelsen, Terry Stark