ISSUE 6 JUNE 10, 1999
In areas of North Dakota where rainfall has been near normal, crops
look fine and fields are
relatively even in greenness. However, in areas which have received over 8 inches of rain in the
past month, there are areas which are yellow, or in some cases whole fields are yellow. As a case
in point, we have studied several fields in the St. Thomas area for several years. Last year and this
year we killed out wheat in small areas throughout a field and sampled every two weeks beginning
the middle of May and continuing until heading to study the release of N from beet tops and the
movement of N through the season within the field. Last year, the May 15 sampling showed that
90% of the 130 lb/acre of N we found in the top foot was in the 0-6 inch surface zone. This year
our May 18 sampling showed only about 10% of the N was in the 0-6 inch depth, about 30% was
in the 6-12 inch depth and the rest of the N was deeper than 12 inches. This is in a fine sandy loam
soil with only about 3 inches of rain during the past month. Any guesses how deep the N is in loamy
soils and coarser in areas with over 6 inches of rain lately? My guess is its deep, and there is concern
about N availability to especially small grains.
In years when rainfall is limiting (not enough moisture), N is
usually in excess because of our
recommendations for optimistic yield goals in most years. In these years, wheat/durum protein levels
are high, because N levels are in excess of the amount necessary for the yield achieved. But in years
in which yields are limited by N and are not limited by too little water, the wheat uses the N to make
what yield is possible at a base-line protein level. When N is limiting, both yield and protein quality
suffer. That is the situation that much of the area is in this year. Producers largely cut back on rates to
begin with, then the rains have resulted in significant denitrification/leaching in the east, and leaching in
the west. Even the tradition higher protein areas of the southwest and northwest parts of the state
have been hit by exceptionally high levels of rainfall since the beginning of May.
It is unclear how the grain trade may react to lower protein coming
from the state this year.
Protein premiums should be watched however to determine whether it might be worthwhile to
supplement fields for additional N immediately after heading to try to achieve another ½ to 1% more
protein. In studies in Carrington and Minot particularly over the past few years, 15 lb N foliar applied
translated into roughly ½ % more protein. Greater than 1% increase in protein with over 30 lb N/a was
not likely. The material was applied ½ and ½ by volume with water. The cut application was relatively
safe in cool weather, but considerable burning was seen on hot days.
Other implications of lower field N levels-
Fields of row crops, particularly corn and sunflower will also
feel the effects of N loss from fields.
Corn can be sidedressed, and Minnesota is encouraging its producers to apply another 50 lb N/acre
generally to compensate for losses from this springs rains. One complication factor is that much of our
corn has been planted past the optimal dates, and so the N rates needed should probably be modified
to be more realistic in yield goal. It is also unwise to over-fertilize corn in this area and north because
of the maturity delays that may result. Sunflower can reach down at least to 4-feet to tap leached N
reserves. However, like any crop, it cannot root into saturated soil zones easily. In coarse textured soils,
it is likely that it could reach deeper N. In heavier soils in the east, the N has probably been lost to
denitrification rather than leaching, the subsoil is probably still saturated and deep rooting is less likely
and deep N may not exist.
Annual forages seeded into these wet fields now and later in the
season as replacements for the planned
but now impractical cash crops should be fertilized with about 15 lb N/acre so that they will be healthy
enough early to hopefully rapidly root down and tap deeper N. If supplemental N is not added, the annual
forage will be lethargic, yellow and basically less nutritional than if N is added.
MICROMIXES AFTER HAIL
A common cottage cure for hail in dry beans and other crops has been
the application immediately
afterwards of micronutrient mixes. Studies in sugarbeet and drybeans at NDSU has not shown any
significant responses to these products after hail-like injury. However, some producers still insist on their
application. The practice seems to be more emotionally therapeutic than scientifically based and should
not be recommended out of hand by trained and knowledgeable consultants and professionals.
We are fast approaching the season for scheduling fertigation with N
on potatoes and corn. These
applications should be based on knowledge of N levels within the crops. Leaf samples and petiole
samples should be taken throughout the field for composite sampling. These samples should not be
taken from the end rows in a bunch. They need to be as representative as possible. It appears as if the
use of timely aerial photography or satellite imagery may help to determine the appropriate locations for
taking these samples and the method is being explored by some crop consultants to reduce the time spent
wandering across the fields. Fertigation should be conducted using amounts of N from 10-30 lb/acre at
each watering, from one to several times during the season.
Dr. Dave Franzen
NDSU Extension Soil Specialist