Plant Population Influence on Yield and Agronomic Traits in ‘Plainsman’ Grain Amaranth*

Grain amaranth, a pseudo-cereal with a rich history as a source of food in Meso America, is an attractive alternative crop suitable to be produced in semi-arid conditions. Grain amaranth production in the United States was 1,800 ha in 1991 (Stallknecht and Schulz-Schaeffer 1991). Most amaranth production is located in the Great Plains, especially in Western Nebraska (Williams and Brenner 1995), a semi-arid region with an average annual precipitation of less than 400 mm. Under these conditions, ‘Plainsman’ is the most widely grown grain amaranth cultivar. Grain yields range from 800 to 1100 kg/ha (Baltensperger et al. 1991; Myers 1994). Currently, there is no commercially available planting equipment for amaranth because of its unusually small seed size (two million seeds/kg). Adapting existing planters for other crops has become a practical solution for the growers. The lowest seeding rate at present is about 1 kg seed/ha. Observations in the field indicates that 2 million plants/ha may be too high. In other crops, reduced grain yield, increased lodging, and lack of plant vigor are problems associated with excessively high plant populations. Previous research conducted on grain amaranth suggests that yield is maximized at low plant populations (60,000 to 75,000 plants/ha) (Duncan and Volak 1979; Mnzava and Ntimbwa 1985; Henderson et al. 1991). However, most of these studies dealt with non-uniform landrace populations or with evaluations under wider row spacings. Identification of plant populations that maximize grain yields in improved cultivars is still an aspect that requires attention. Information obtained from these studies might be useful for the design of equipment capable of seeding more appropriate plant populations. The objective of this study was to evaluate the effect of plant population on grain yield and some agronomic components of ‘Plainsman’ grain amaranth.