Double–cropping with a pea–forage mixture
Double-cropping is one strategy for maximizing productivity of a field. In double cropping systems, two crops are harvested from the same field in a single season. In a typical rotation, a fall–seeded cool–season crop is harvested for biomass in late spring and directly followed by a warm–season crop. By expanding the growing season to include late fall and early spring, biomass yield increases over single–cropping systems may be as large as 25% (Heggenstaller et al. 2009). Double–cropping can also improve nutrient uptake in N– or P–saturated soils, reducing nitrate run–off as well as saving on fertilizer costs (Krueger et al. 2010).
However, harvest dates of cool–season crops can have significant impacts on grain yields. Double-cropping may delay planting date by 2–6 weeks, resulting in a shortened growing season for warm–season crops and reducing grain yield. In this context, forages are well adapted to double–cropping rotations; two harvests of forage biomass can provide higher financial returns per acre than a single grain crop.
Due to its extreme winter temperatures and short growing season, Minnesota's climate provides unique challenges for growers looking to incorporate high-value forages into their management practices. Several strategies may increase the profitability of double-cropping in Minnesota. The incorporation of legumes in a forage crop can greatly increase its feed value over sole-cropped crops such as winter rye (Strydhorst et al., 2008). Additionally, the roots and stubble of a legume-cereal mix may provide a significant source of nitrogen to subsequent warm-season crops, reducing the need for N-fertilizer costs and increasing returns per acre. However, few legumes are winter-hardy in Minnesota. Legume-cereal mixes must be planted in the spring, which may result in an even longer delay in warm-season crop planting than in typical double-cropping systems. This delay could be managed by using early maturating grain cultivars .
Current research at the University of Minnesota is investigating whether the combination of high–value spring planted forages, reduced N-fertilizer applications, and early-maturing corn varieties can increase the profitability of double-cropping in Minnesota and compete favorably with traditional full-season corn rotations.
A pea-barley forage mix, chosen for its high yield and excellent feed value was planted in March of 2014. At maturity, it was harvested for forage, and followed by one of three early-maturing summer crops: A dual purpose silage/grain corn (Pioneer 8906 AM1), a recently developed semidwarf corn (Schaefer et al. 2011) and soybean.
The corn varieties were exposed to six N rates, ranging from 40 lbs N per acre to 200 lbs N per acre. Corn was harvested for grain (semidwarf corn and full-season corn) and silage (Pioneer 8906 AM1) in October. Winter rye was planted after harvest, and will be harvested for forage again in the spring of 2015. The study will be replicated at two locations in 2015.
Forage Pea Project Objectives
- Compare grain yields and total biomass production of a spring forage – short–season grain – winter rye rotation to a full–season corn – winter rye rotation.
- Determine nitrogen use efficiency of double–cropping rotation to full–season corn.
- Assess economic viability of a double–cropping rotation for farmers based on forage quality, grain/silage yield and input costs.
Weather posed substantial challenges during this past growing season. The cool, wet spring delayed spring forage harvest until June 30; summer crops were not planted until July 1. Although the full-season corn and 62-day semi-dwarf variety reached maturity by early October, the dual–purpose variety did not mature, and was harvested for silage.
Full–season corn performed well, as it did not experience delayed planting. It yielded 178 bushels per acre, well within 2014 county averages (Table 1). Planting date had strong effects on corn silage yields. In 2014 corn silage variety trials conducted by the University of Minnesota, similar corn silage varieties yielded over 30 tons per acre; a 50 percent yield reduction can be explained by a delayed planting; planting in late June can typically result in a decline in yield of at least 40 percent. Semi–dwarf corn did not yield as expected. In previous university trials, it yielded over 150 bushels per acre (Schaefer et al. 2011). Planting date and poor stand establishment help explain the poor yield of this variety. Cool, wet spring weather can also explain relatively low forage yields.
Table 1. Summary of treatments, planting dates, harvest dates, and yield, 2014.
|Pea/barley DM yield
|Crop planting date||Crop harvest date||
|Full season corn||102||–||–||–||May 6||Oct. 8||Grain||178 bu/a|
|Dual purpose corn||89||May 5||June 30||3.5||July 2||Oct. 8||Silage||15 ton/a|
|Dwarf corn||62||May 5||June 30||3.5||July 2||Oct. 8||Grain||25 bu/a|
|Soybean||0.6||May 5||June 30||3.5||July 2||Oct. 8||Grain||–|
Heggenstaller, et al., 2009. Growth analysis of biomass production in sole–crop and double–crop corn systems. Crop Science 49:2215-2224.
Krueger, et al., 2010. Growth stage at harvest of a winter rye cover crop influences soil moisture and nitrogen. Online. Crop management doi:10.1094/CM-2010-1014-01-RS.
Schaefer, et al., 2011. Breeding potential in semi–dwarf corn for grain and forage in the northern U.S. corn belt. Crop Science 51:1637-1645.
Strydhorst, et al., 2008 Forage potential of intercropping barley with faba bean, lupin, or field pea. Agron J. 100:182-190.
As the study progresses, future results will be presented at University of Minnesota Extension Forages Website.
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