Revisiting alfalfa planting dates for the semiarid U.S. Southwest

Abstract

Alfalfa (Medicago sativa) growers in the southwestern United States desire to match irrigation allocations better and to recover at least some of the establishment costs in the seeding year by spring planting. Randomized complete block studies at Tucumcari and Los Lunas, NM compared planting date effects on seeding year and subsequent production year yields and seeding year economics. Seeding year yields in each test were statistically separated by the number of harvests taken. The earliest planting at Los Lunas produced 11.3 Mg ha −1 over three harvests in the seeding year to fully recover establishment and harvesting costs, and two harvests (4.3 Mg ha −1 ) from the earliest planting at Tucumcari recovered approximately half the costs. Production year yields from spring and late-summer to early autumn seedings at Los Lunas were generally not different, but greater than 25 June and 21 July plantings (2-yr mean yields for planting dates were 22.8, 22.1, 20.5, 21.2, 23.3, 21.8, and 22.5 Mg ha −1 , respectively; P < .0001, SEM = 0.4). Four-year average production year yields at Tucumcari were statistically separated into spring, early to mid-summer, and late summer plantings planting dates, respectively; P < .0001, SEM = 0.8). Spring planting can potentially increase seeding year yields as well as throughout the stand life.Abbreviations: DAP, days after planting; DM, dry matter; FD, fall dormancy; TNC, total nonstructural carbohydrates; VSP, vegetative storage proteins.

Alfalfa Rotation Strategy and Soil Type Influence Soil Characteristics and Replanted Alfalfa Yield in the Irrigated Semiarid, Subtropical Southwestern USA

“…The results of statistical analysis for total annual DM yield data are presented in Table 4, which shows significant effects for Rotation and the Test x Rotation interaction. Annual alfalfa DM yields in these Tests were slightly less than those measured in other studies at this location for alfalfa planted in mid-September [25]. Differences are likely due to alfalfa variety, irrigation technique and amount, soil test, and other environmental influences.…”

“…Seguin et al [7] reported that a 2-week delay in planting after plowing led to reduced yields compared to planting immediately. Lauriault et al [25] reported long-term reduced yield associated with a delayed planting date on 3-week intervals from spring into autumn on land not previously in alfalfa at one location, as did Seguin et al [7], due to initial stand density for mid-summer plantings at another location. They [7] also reported that yields in the year after the seeding of alfalfa immediately following alfalfa were less than yields of alfalfa following a control crop, suggesting that the effects of autotoxicity may be delayed and become expressed later through autoconditioning [5,7].…”