Effect of Establishment Method, Variety , and Seeding Rate on the Production and Quality of Alfalfa Under Dryland and Irrigation1

Abstract

AbstractEstablishment of alfalfa (Medicago sativa L.) with small grain companion crop is not always satisfactory. This study was designed to compare alternative establishment methods and determine the influence of alfalfa varieties and seeding rates on dry matter and crude protein production and herbage quality. The relationship between alfalfa plant density and root+crown weight and their effect on forage yield were evaluated.Pure stands of alfalfa were established by four methods: 1) no herbicide or companion crop (check); 2) a plant herbicide, S‐ethyl dipropylthiocarbamate (EPTC); 3) a companion crop of oats (Arena sativa L.) harvested for forage; and 4) a companion crop of oats harvested for grain. Three alfalfa varieties were evaluated: T3X‐8 hybrid, ‘Saranac,’ and ‘Vernal.’ Four alfalfa seeding rates were compared: 4.5, 9.0, 13.5, and 17.9 kg/ha of purelive‐seed (PLS). Studies were conducted at three locations in South Dakota. Experiments at Gayville and Norbeck were under dryland conditions and at Brookings under irrigation.Alfalfa established with oats harvested for forage yielded the most weed‐free forage dry matter during the seeding year. This was followed in descending order by the yields of alfalfa established with EPTC, the check, and oats harvested for grain. Herbage crude protein yields were similar during the seeding year regardless of establishment method, except for the oat grain treatment which was lower. Second‐year alfalfa dry matter and protein production were not affected by establishment method.Dry matter yields were higher for Saranac and T3X‐8 hybrid alfalfa than for Vernal when moisture was optimum and winter injury did not occur. Under dryland, there were no differences in yield among the three varieties. T3X‐8 was generally lowest in crude protein content; Vernal was highest in protein late in the season.With irrigation, higher dry matter and crude protein yields were obtained during the seeding year at each increase in seeding rate. Under dryland, no differences in yield were noted above the 13.5 kg/ha rate during the seeding year. Second‐year alfalfa yield~ increased at seeding rates up to 9.0 kg/ha of PLS at Gayville and Brookings, and up to 13.5 kg/ha at Norbeck. Generally, herbage crude protein content was not affected by seeding rate. Root+crown weights of alfalfa decreased as seeding rates increased up to 13.5 kg/ha.