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Triticale the Nineteenth Crop of a Dryland
Rotation Without Summer Fallow
M.F. Vigil, R.A. Bowman, A.D. Halvorson
PROBLEM: Conservation tillage has increased annual soil
water storage. This enables the use of annual cropping for some soils of the
central Great Plains. Annual cropping entails greater biomass production which
increases surface crop residues impacting soil quality and soil water storage.
This study was designed to evaluate long term changes in soil C and N under
annually cropped dryland conditions under different N fertility. Short term, the
study allows for the estimation of N use efficiency and fertilizer N
requirements of various dryland crops.
APPROACH: This is the 18th year of the experiment
(started by Ardel Halvorson in 1983), where under dryland conditions, the site
is cropped continuously with no summer-fallow on a Weld silt loam. The site was
a barley-corn rotation until 1992 when oats for hay replaced barley. We have had
15 successful years and three failures in the 17 years of cropping: winter wheat
was grown in 1988 to replace a hailed out corn crop in 1987, in 1990, poor stand
and aphids limited barley yields to 21 bu/acre, and in 2000,
Round-up-ready-soybeans (category 3) made between 8 and 13 bushel. The
experiment is a 4-rep RCB where the only treatment is N fertilizer rates of 0,
20, 40, 60, 80 or 120 lbN/acre. The study is managed with no-till to conserve
water, and weed control has been through the use of contact and residual
herbicides. Phosphorous (P) nutrition has not been limiting but low rates of P
have been applied with the seed at planting or as broadcast treatments. Soil
profile water and nitrates are monitored annually to determine N balance and
water use efficiency.
RESULTS: In 2002, triticale biomass yields were less than
500 lbs/acre due to drought. In 2001 roundup ready (DK493)Corn made 87 bushel
with 80 lbs of N (table 1). Yields tended to increase with increasing N rate.
Through the years, the optimum N rate for the grain crops has been between 40
and 60 lbs N/acre for wheat and between 60 and 80 lbs for corn.
Table 1. Yields of dryland corn as affected by N rate in 2001
under no-till annual cropping.
|
N rate |
Grain Yield |
Test wt |
|
lbs /acre |
bushels/acre |
lbs/bushel |
|
0 |
68 |
55 |
|
20 |
77 |
55 |
|
40 |
81 |
55 |
|
60 |
85 |
55 |
|
80 |
86 |
54 |
|
120 |
88 |
54 |
A buildup of excess nitrate-N can be found in the soil of
plots fertilized at 80 lbs or more. These results suggest that with this soil
(under dryland conditions) annual fertilizer N rates greater than 80 lb/acre,
are excessive for the crops and management currently available. Triticale yields
in 1995 were 5.5 ton/acre at an optimal N rate of 80 lb/acre. In 1996, maximum
corn grain yields of 90 bu/acre were measured at the 120 lb N rate. At the 80 lb
N rate 75 bu/acre of grain was harvested. In 1997, on 11, July we harvested 900
to 1100 lbs of profi peas with a whole plot average of 1011 lbs/acre. The 1998
crop of winter wheat averaged 26 bushels in the fertilized plots and 22 bushels
in unfertilized plots. Corn yields in 1999 were as high as 140 bushels per acre
at the 80 and 100 lb N rates. Warm season grasses (sandbur) are becoming a
nuisance. In 2000, roundup ready soybean (maturity group 3) was used to help
eliminate the sandbur problem. The soybeans were not fertilized with N because
residual N levels were large from fertilization in prior years. A visual
response of the soybean was observed. The lowest yields were measured in the 80
and 120 lb N/acre plots (8 bushel/acre). The largest yields were measured in the
0 N-rate plot (13 bushel/acre).
FUTURE PLANS: The crops for the next few years will be dormant seeded
winter wheat or spring triticale, Round-up ready corn and dry edible beans or
millet. The experiment will continue for another 4 years to evaluate long-term
soil C and N changes under high N management and high productivity. The
author may be reached via e-mail at: M.F.
Vigil
or phone: 970-345-2259. |