Fertilizer Nitrogen Use Efficiency Using
Alternative Legume Interseeding in Continuous Corn
Thomason, D.A. Keahey, K.J. Wynn,
alternative management systems have been evaluated for corn (Zea
mays L.), soybeans (Glycine
max L.), and wheat (Triticum
aestivum L.) production, however, most have involved rotations
from one year to the next. Legume
interseeding systems which employ canopy reduction techniques in corn
have not been thoroughly evaluated.
One study was initiated in 1994 at the Panhandle Research
Station near Goodwell, OK, on a Richfield clay loam soil, to evaluate
five legume species: yellow sweet clover (Melilotus officinalis L.), subterranean clover (Trifolium
subterraneum L.), alfalfa (Medicago
sativa L.), arrowleaf clover (T.
vesiculosum L.) and crimson clover (T.
incarnatum L.) interseeded into established corn.
In addition, the effect of removing the corn canopy above the
ear (canopy reduction) at physiological maturity was evaluated.
Canopy reduction increased light interception beneath the corn
thus enhancing legume growth in late summer, early fall, and early
spring the following year prior to planting.
Legumes incorporated prior to planting were expected to lower
the amount of inorganic nitrogen fertilizer needed for corn
clover appeared to be more shade tolerant than the other species, and
intereseeding this species resulted in the highest corn grain yields
when no N was applied. In the last two years, interseeding crimson clover at
physiological maturity, followed by canopy reduction resulted in a 21
bu/ac increase in yield compared to conventionally grown corn with no
reduction has been used in third world countries as a means of
increasing light interception for a relay crop.
Canopy reduction is imposed when the corn reaches physiological
maturity when nutrient and water uptake has ceased).
Over the past 20 years, various researchers have evaluated
intercropped legumes for increased N supply in corn (Zea
mays L.) production. As
sources of inorganic nitrogen fertilizer become less dependable and
prices increase, organic forms, particularly legumes, are being
considered as alternative sources for non-legume crops.
Searle et al. (1981) stated that corn grain yield was not
affected by legume intercrop, indicating neither competitive
depression nor nitrogen transfer from the legume.
Nair et al. (1979) showed that intercropping corn with soybeans
increased yield 19.5% when compared to monoculture corn.
Scott et al. (1987) noted yields following medium red clover (T.
pratense L.) were equivalent to the addition of 17 kg ha-1
though intercropping usually includes a legume, applied nitrogen may
still confer some benefits to the system as the cereal component
depends heavily on nitrogen for maximum yield (Ofori and Stern, 1986). Chowdhury and Rosario, (1993) found that intercropping corn
with mungbeans (Vigna radiata
L.) increased yields 71% when the N application rate was increased
from 0 to 90 kg/ha. Ebelhar
et al. (1984) reported with no fertilizer N applied, there was an
increase in corn grain yield from 2.5 to 6.2 Mg ha-1 with
hairy vetch (Vicia villosa L.) treatment compared with corn residue.
Corn yields increased 62% with applied N (0 versus 120 kg N ha-1).
reduction is defined as the removal of the corn canopy just above the
ear at physiological maturity, where the cut portion is allowed to
drop to the soil surface. Some
of the basis of canopy reduction come from regions where a relay crop
like common beans is produced following corn.
In order to increase light interception beneath the corn canopy
for the bean plant, the tops of the corn can be removed once
physiological maturity is reached.
This in turn does not sacrifice the corn yield while increasing
the chances of producing a bean crop that would not have been possible
if planting took place following corn harvest.
The objective of this work was to
evaluate the effect of interseeded legume species and nitrogen rates
combined with canopy reduction on corn grain yield and grain protein.
experiment was established in the spring of 1994 at the Oklahoma
Panhandle Research and Extension Center near Goodwell, OK on a
Richfield clay loam (fine, montmorillonitic, mesic Aridic Argiustoll).
Initial soil test characteristics and soil classification are
reported in Table 1. A
randomized complete block experimental design with three replications
was used. Plot size consisted of four rows (30 inch) x 25 ft.
All treatments received 90 lb N/ac of urea (45-0-0) in the fall
of 1995. In 1996 and for
the remaining years of this experiment, treatments 1-5, 7 and 12
received no N to assess legume N fixation compared to identical
treatments with 45 lb N/ac. Each
year, corn was planted at a seeding rate of 30,000 seeds ac between
late April and early May.
reduction was imposed by removing the tops of the corn plants just
above the ear using a machete. This
allowed sunlight to reach the legume seedbed.
In August, when the corn had reached physiological maturity,
five legume species were interseeded by hand at the following seeding
rates: yellow sweet clover (Melilotis
officinalis L.) 40 lb/ac, subterranean clover (Trifolium
subterraneum L.) 40 lb/ac, alfalfa (Medicago
sativa L.) 30 lb/ac, arrowleaf clover (T.
vesiculosum L.) 20 lb/ac and crimson clover (T.
incarnatum L.) 40 lb/ac. Physiological
maturity was determined by periodic monitoring grain black layer
interseeding and canopy reduction, 5 cm of irrigation water was
applied for legume establishment and to prevent reduction in growth
caused by moisture stress. The
legume seeds were inoculated prior to planting with a mixture of Rhizobium
meliloti and R. trifolii
bacteria. Harvest area
consisted of two rows (30 inches) x 25 ft.
Harvesting and shelling were performed by hand.
Plot weights were recorded and sub-sampled for moisture and
chemical analysis. Subsamples
were dried in a forced-air oven at 150°F and ground to pass a 140
mesh screen. Total
nitrogen concentration was determined on all grain samples using dry
combustion (Schepers et al. 1989).
Protein N in corn grain can be determined by multiplying %N by
legumes remained in the field until the following spring when they
were incorporated prior to corn planting using a shallow (4 inches)
disk. Legumes were only
used for ground cover and potential nitrogen fixation and as such were
not harvested for seed or forage.
imposing the alternative management practice of canopy reduction, we
visually observed an increase in light interception beneath the corn
canopy, thus enhancing legume growth in late summer, early fall before
corn harvest, and early spring the following year prior to planting.
Crimson clover had superior spring growth compared to the other
species evaluated as visual biomass production was greater when
incorporated in early April prior to planting.
No grain yield response to applied N was observed in 1996, or
1997, but by 1998, yields increased 21 bushels as a result of applying
N (12 vs 13, Table 2). The
lack of fertilizer N response at this site restricted the early
evaluation of legume N contribution and species comparison.
was no significant difference between grain yields when tops were cut
at physiological maturity compared to the normal practice (5 vs 7,
crimson clover with and without canopy reduction, with no N applied)
in 1996, 1997 or 1998. However,
by 1999, interseeding crimson clover and using canopy reduction
resulted in increased yields when compared to that observed where no
canopy reduction was employed. It was important to find no differences between canopy
reduction and conventional management early on, because it
demonstrated the applicability of interseeding in late summer.
In the last two years, interseeding
crimson clover at physiological maturity, followed by canopy reduction
resulted in a 21 bu/ac increase in yield when compared to
conventionally grown corn with no N applied (5 versus 12).
This N fertilizer savings of approximately 24 lb N/ac would
have an economic value of $4.80.
Legume interseeding and canopy reduction costs would likely be
greater than $4.80, thus restricting what can be promoted at this
point in time.
not evaluated in this study, mechanized canopy reduction could
decrease the time required for grain to lose moisture since more
sunlight would directly come in contact with the corn ears when the
tops were removed. When
grain moisture is high it can delay harvest and/or significantly
increase drying costs. Legume seeding rates, alternative species, method of
interseeding and interseeding date will all need to be thoroughly
evaluated prior to the mechanization and implementation of this
nitrate leaching and soil erosion are becoming major concerns in
production agriculture today, this experiment may lead to practices
that can decrease both, via lowering the amount of inorganic
fertilizer N needed for corn production and reducing the amount of
bare soil susceptible to wind and water erosion.
M.K. and E.L. Rosario. 1994. Comparison
of nitrogen, phosphorus and potassium utilization efficiency in maize/mungbean
intercropping. J. of
Agric. Sci., Cambridge. 122:193-199.
S.A., W.W. Frye and R.L. Blevins.
from legume cover crops for no-tillage corn.
Agron. J. 76:51-55.
K.P., U.K. Patel, R.P. Singh and M.K. Kaushik.
of legume intercropping in conservation of fertilizer nitrogen in
maize culture. J. Agric.
Sci. Camb. 93:189-194.
Francis and W.R. Stern. 1986. Maize/cowpea
intercrop system: effect of nitrogen fertilizer on productivity and
efficiency. Field Crops
J.S., D.D. Francis and M.T. Thompson.
determination of total C, total N and 15N on soil and plant material.
Commun. Soil Sci. Plant Anal.
T.W., J. Mt. Pleasant, R.F. Burt and D.J. Otis.
of ground cover, dry matter, and nitrogen from intercrops and cover
crops in a corn polyculture system.
Agron. J. 79:792-798
P.G.E., Yuthapong Comudom, D.C. Shedden and R.A. Nance.
1981. Effect of maize + legume intercropping systems and fertilizer
nitrogen on crop yields and residual nitrogen.
Field Crops Res. 4:133-145.
1. Initial surface (0-15
cm) soil test characteristics and soil classification at Goodwell, OK.
Richfield clay loam (fine, montmorillonitic, mesic Aridic