Methods for Establishing Legumes on Sandy Soils

Crop establishment is a major concern for producers who grow legumes on sandy soils. This study was conducted on a Verndale sandy loam (coarse-loamy, mixed Udic Argiboroll) to evaluate the impact of five methods of establishment on the production of four legumes (alfalfa [Medicago sativa L.], birdsfoot trefoil [Lotus corniculatus L.], cicer milkvetch [Astragalus cicer L.], red clover [Trifolium pratense L.]). Methods varied from the use of a clean, prepared seedbed to no-till seeding into small grain stubble. The study was initiated in 1991 and repeated in 1992. Yields from spring seedings were measured in the year of establishment. Dry matter yields were also measured for two residual years following establishment. Stand counts were taken in the fall of 1992. Yields of all legumes measured in the year of establishment were generally higher when there was no competition from a companion crop. In general, yields of alfalfa and red clover were equal but higher than yields of birdsfoot trefoil and cicer milkvetch when all establishment methods are considered. Stand counts showed that all establishment methods produced an acceptable stand of all legumes. Measured stand, however, was not directly related to forage yield. The results of this study show that there are several methods that can be used to successfully establish legumes on sandy soils. Choices for individual forage producers will be highly dependent on erosion potential and crops grown for the total farming system. Establishment is frequently identified by producers as a major problem in developing profitable forage crop enterprises. This problem is especially challenging where legumes are to be seeded on droughty, sandy soils. Several potential methods for establishing commonly used forage legumes are possible. Using modem herbicides and tillage systems adapted to Minnesota conditions, these methods involve the seeding of legumes in either early spring or early August. The primary objective of this study was to evaluate the effect of five potential seeding methods on stand establishment and subsequent yield of four popular forage legumes. Literature SummarySeveral studies have evaluated the effect of various establishment methods on emergence of forage legumes and subsequent yields. Some used a companion crop and others used various herbicides. Most of these studies, however, have been conducted where soils were not sandy and soil moisture was not limiting. In addition, the impact of no-till establishment methods using residue of a small grain crop to preserve soil moisture had not been fully researched with sandy soils. Therefore, further evaluation of establishment methods that could be used for sandy soils was needed. Study DescriptionThis study was conducted on a Verndale sandy loam at the University of Minnesota Irrigation Center at Staples. Four forage legumes (alfalfa, birdsfoot trefoil, cicer milkvetch, red clover) were seeded in early May and early August of 1991 and 1992, using five seeding methods for legume establishment. These were; (i) solo seeded, (ii) oat seeded as a companion crop harvested for grain, (iii) an oat mulch system removing the oat crop with sethoxydim, (iv) late summer seeding with an oat companion crop, and (v) late summer no-till. Forage production resulting fiom the use of methods i, ii, and iii, which involved seeding in early spring, was measured in the seeding year. Forage production for two residual years following seeding was measured by harvesting three cuttings of alfalfa and two cuttings of all other legumes each year. Stand was evaluated by digging and counting plants fiom a 1.5 sq ft area in each plot in the fall of 1992. Applied QuestionAre there establishment methods that can be used to obtain a satisfactory stand of various forage legumes seeded in a sandy soil? Results of this study show that a variety of establishment methods can be used to achieve a satisfactory stand of four common forage legumes. These methods range from no-till to the use of a prepared seedbed combined with a herbicide application. In the establishment year, highest forage yields were produced by alfalfa and red clover. Yields were generally higher when legumes were planted without a companion crop. However, all spring seeding methods evaluated resulted in high levels of forage production from alfalfa, birdsfoot trefoil, and red clover in the seeding year (Table 1). Forage growth was not adequate for harvest when the legumes were seeded in early August. Forage production from cicer milkvetch was not adequate for harvest when the legume was established in 1991. The establishment methods used exhibited inconsistent effects on forage production measured for 2 yr after seeding. Stand counts, however, revealed that all of the methods produced a satisfactory stand for each legume studied. RecommendationsBased on the results of this study, there are a variety of establishment methods that can be used on sandy soils to obtain a satisfactory stand of four legumes. The solo-seeding technique is appropriate where water or wind erosion are not major concerns. The no-till method using stubble from a small grain crop would be appropriate where soil erosion is a major concern. This no-till method is also appropriate where residue from a small grain crop remaining on the soil surface reduces water loss by evaporation, thereby enhancing the potential for successful establishment. Table 1The effect of three establishment methods used in the spring on the yield of three legumes. Staples, MN. 1991–1992 average. LegumeEstablishment methodAlfalfaBirdsfoot trefoilRed clover----------ton dry matter/acre----------Solo2.361.482.50Oat companion crop2.080.961.60Oat removed with sethoxydim1.771.301.90