Establishment and First Year Yield of Interseeded Alfalfa as Influenced by Corn Plant Density and Treatment with Prohexadione, Fungicide and Insecticide

John H. Grabber,William R. Osterholz,Mark J. Renz,Damon L. Smith

doi:10.3390/agronomy11112343

Abstract

Interseeding alfalfa (Medicago sativa L.) into a silage corn (Zea mays L.) companion crop can increase the yield and profitability of forage production and reduce the risk of nutrient and soil loss from cropland, but unreliable establishment of alfalfa hampers the adoption of this practice on dairy farms. This study evaluated plant survival, foliar health, and dry matter yields of two alfalfa varieties when established in corn sown at populations ranging from about 47,500 to 100,000 plants per ha−1 and when treated with prohexadione (PHD), PHD followed by fungicide and insecticide (PHD-FI), or not treated with agrichemicals. The plant density of alfalfa during establishment was adversely impacted by above average precipitation and high corn populations, but substantially improved by PHD-FI treatment, which limited alfalfa etiolation, disease, and defoliation. First-cut dry-matter yields of interseeded alfalfa after corn were maximized at a stand density of approximately 200 plants m−2 or 850 stems m−2 and total first year yield exceeded conventionally spring-seeded alfalfa by 59 to 75%. Overall, our results indicated that PHD-FI treatment promoted good establishment and subsequent forage production of interseeded alfalfa. Applications of PHD-FI must, however, be fine-tuned, and additional management practices must be developed to ensure both good yields of corn silage and reliable establishment of interseeded alfalfa, especially during wet growing conditions.

Highlights

Growing corn silage in rotation with alfalfa provides a blend of forage that enhances milk production while providing other benefits, including lower inputs for fertilizer nitrogen and pest control as well as improved soil quality and soil conservation
The primary period of first-year alfalfa forage production from May through August occurred under temperatures that were 8% above normal in 2018 and near normal in 2019, while precipitation during this period was 40 and
Dry matter yields of corn silage in September were affected by a year X corn population interaction; yields averaged 19.21 Mg ha−1 in 2017 and were not influenced by corn population, but, in 2018, yields increased quadratically from 17.5 to 23.0 Mg ha−1 as corn population increased (Figure 1)

Summary

Introduction

Growing corn silage in rotation with alfalfa provides a blend of forage that enhances milk production while providing other benefits, including lower inputs for fertilizer nitrogen and pest control as well as improved soil quality and soil conservation. Seeding small grains or other commonly used companion crops with alfalfa can modestly improve forage production during the establishment year, but forage quality is often reduced [5,6,7]. One way to circumvent the low establishment year yields of alfalfa would be to use corn silage as a relatively high-yielding and high-quality companion crop. In this system, alfalfa is interseeded to serve as a highly effective cover crop for corn, and it is brought into full forage production the following year. The successful interseeding of alfalfa reduces the risk of soil and nutrient loss from cropland, suppresses weeds, and increases the overall forage yields and profitability of corn silage–alfalfa rotations [8,9,10,11,12,13,14,15]

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