A Comparison of Pigeonpea and Cowpea Forage Yield and Nutritive Value in the Southern High Plains of the USA Bulletin 802 Leonard M. Lauriault, Sangu V. Angadi, Mark A. Marsalis, Dawn M. VanLeeuwen1 Agricultural Experiment Station • College of Agricultural, Consumer and Environmental Sciences High Plains of the USA and similar higher elevation, Department of semiarid, subtropical environments. Plant and Environmental Sciences AbStrACt INtroDUCtIoN Few options of warm-season annual legumes are Forage sorghum [Sorghum bicolor (L.) Moench] available for the higher elevations of semiarid, sub- and sorghum x sudangrass (S. bicolor var. Sudanese) tropical regions such as the Southern High Plains are important warm-season annual forage grasses of the USA; therefore, candidate species must be in the higher elevations of the semiarid, subtropi- explored for these environments. Pigeonpea [Cajanus cal Southern High Plains of the USA (eastern New cajan (L.) Millspaugh] has not been evaluated for Mexico and Texas Panhandle) because they are rela- forage in this environment, and pigeonpea forage tively drought-tolerant and productive. However, yield and nutritive value have not been compared there are limitations regarding crude protein (CP) with those of cowpea [Vigna unguiculata (L.) Walp- concentration and other nutritive value compo- ers], which is currently the most commonly used nents, such as fiber and digestibility, and livestock warm-season annual legume in the region. Pigeonpea may require supplementation if these components (GA-2) and cowpea (Iron and Clay) were compared are too low (Mislevy et al., 2005; Contreras-Govea in separately analyzed randomized complete block et al., 2009). Some of these deficiencies in nutri- studies conducted in 2006 and 2007 at New Mexico tive value can be alleviated by including legumes State University’s Agricultural Science Center at in the forage system (Muir, 2002; Lauriault and Tucumcari using different fields and irrigation tech- Kirksey, 2004; Contreras-Govea et al., 2009). Few niques each year. Cowpea was superior to pigeonpea warm-season annual legumes are adapted to humid, for forage yield in 2006 and had numerically higher subtropical regions (Mislevy et al., 2005). There yield in 2007 [6.39 vs. 3.59 Mg ha-1 for cowpea and are even fewer options for semiarid, subtropical re- pigeonpea, respectively, in 2006 (P <0.01) and gions, and additional potential forage legumes must 5.07 vs. 4.06 Mg ha-1 in 2007 (P <0.30)]. Forage be explored (Muir, 2002; Lauriault and Kirksey, nutritive value of cowpea was greater than pigeonpea 2004; Contreras-Govea et al., 2009). in both years as estimated by crude protein [189 vs. Soybean (Glycine max L.) is widely adapted; 156 g kg-1 in 2006 (P <0.05) and 130 vs. 88 g kg-1 in however, drought limits its forage yields (Ishibashi 2007 (P <0.01)] and neutral detergent fiber [323 vs. et al., 2003; Mislevy et al., 2005), and the combi- 467 g kg-1 in 2006 (P <0.05) and 440 vs. 505 g kg-1 nation of high temperature and low humidity in in 2007 (P <0.05)]. Based on these results, cowpea the Southern High Plains increases the irrigation remains the better option than pigeonpea for forage requirement for soybean and reduces grain yield production systems under irrigation in the Southern (C. Trostle, personal communication, 2009). 1Respectively, Forage Agronomist, Agricultural Science Center at Tucumcari (corresponding author; [email protected]); Crop Stress Physiologist, Agricultural Science Center at Clovis; Extension Agronomist, Agricultural Science Center at Clovis; and Agricultural Biometrician, Agricultural Biometrics Service, Agricultural Experiment Station, all of New Mexico State University. To find more resources for your business, home, or family, visit the College of Agricultural, Consumer and Environmental Sciences on the World Wide Web at aces.nmsu.edu Cowpea [Vigna unguiculata (L.) Walpers] is well of Georgia, Athens, GA) to that of ‘Iron & Clay’ adapted to low soil moisture situations (Muir, cowpea (Turner Seed, Breckinridge, TX). Different 2002), but not wet soils (Mislevy et al., 2005). fields with different soil types and irrigation tech- Lauriault and Kirksey (2007) found that black- niques were used each year. The change in fields eyed cowpea grown for edible dry beans was well was warranted to avoid volunteerism by the crops adapted to the Southern High Plains, with no from the previous year and a change in available grain yield reduction if planted before mid-June irrigation techniques. Seeding rates were calculated or if furrow irrigation or precipitation were timely, to establish 150,000 and 111,000 plants ha-1 for albeit limited. Data published by Contreras-Govea cowpea (Mislevy et al., 2005) and pigeonpea (Bid- et al. (2009) indicate that forage cowpea has the lack et al., 2006), respectively. Uninoculated seed potential to significantly improve nutritive value of was used for both studies because it was speculated monoculture sorghum forages. that nodulation by either species could be poor Pigeonpea [Cajanus cajan (L.) Millspaugh] is locally due to soil factors. The average annual also a widely adapted legume, but it prefers cli- temperature and precipitation for this location are mates with an annual average temperature of 19°C 14.4°C and 404.1 mm, respectively (Kirksey et and soils with 240 mm available water holding al., 2003). The precipitation pattern in the area is capacity at higher elevations (Mligo and Craufurd, continental, with approximately 80% (302.1 mm 2005), which are prevalent in the Southern High on average) falling from April through September Plains. Rao et al. (2003) and Mligo and Craufurd (Kirksey et al., 2003). Weather data were collected (2005) found that pigeonpea was least adapted to from a National Weather Service station located wet soil conditions, similar to cowpea (Mislevy et within 1 km of the study areas (Figure 1). al., 2005). Consequently, pigeonpea has recently In 2006, the soil was Canez fine sandy loam been promoted for grain and forage in the south- (fine-loamy, mixed, thermic Ustollic Haplargid), ern Great Plains (Rao et al., 2003; Bidlack et al., and the previous crop was sorghum x sudangrass 2006; Rao and Dao, 2008). But that region has that had followed a 7-year-old alfalfa (Medicago lower elevations than the Southern High Plains sativa L.) -grass mixture. Soil testing indicated a [approximately 400 m (Muir, 2002; Rao et al., pH of 8.4 and N, P, and K levels of 10, 19, and 2003; Bidlack et al., 2006) vs. approximately 210 ppm, respectively, in the surface 30 cm. The 1,300 m (Lauriault and Kirksey, 2004; Contreras- seedbed was conventionally tilled and formed Govea et al., 2009) for the southern Great Plains into beds on 0.91-m centers for furrow irrigation. -1 and the Southern High Plains, respectively] and Fertilizer (116-58-0 kg N-P2O5 -K 2O ha ) was ap- higher precipitation [May through September, 500 plied preplant and incorporated, and was based on mm in the southern Great Plains (Rao et al., 2003) soil test recommendations for sorghum forage and vs. 280 mm in the Southern High Plains (Kirksey because the legume seed was not inoculated. There et al., 2003)]. were four randomized complete blocks in which No data are available about pigeonpea perfor- individual plots were 15.24 x 3.66 m, with a single mance in the Southern High Plains of the USA. row planted down the center of each of the 4 beds. Consequently, the objective of this study was to Planting took place 25 May using a 4-row John compare forage yield and nutritive value of Deere flex-planter with a seed-metering cone on pigeonpea and cowpea in the Southern High each planting unit. Furrow irrigations were applied Plains environment. every other week from planting until mid-August to achieve field capacity with each application for a to- tal estimated application of approximately 457 mm. MAtErIALS AND MEtHoDS Micronutrient deficiency was apparent early in the Studies were conducted in 2006 and 2007 at the growing season, and was most pronounced on cow- New Mexico State University Agricultural Science pea. Consequently, a commercially available micro- Center at Tucumcari, NM (35.20° N, 103.68° W; nutrient solution (HiYield Liquid Iron and Other elev. 1,247 m), to compare forage production and Micronutrients, Voluntary Purchasing Groups, nutritive value of ‘GA-2’ pigeonpea (University Bonham, TX) containing Cu, Fe, Mn, S, and Zn bulletin 802 • Page 2 Figure 1. Mean monthly air temperatures and total monthly precipitation during 2006 and 2007 and the long-term (1905–2005) averages at Tucumcari, NM, in the semiarid, subtropical Southern High Plains of the USA. was applied foliarly to all plots at the labeled rate for the growing season. Micronutrient deficiency after two of the irrigations. was not observed. In 2007, the soil type was Redona fine sandy loam A section (3.05 m in 2006 and 2.0 m in 2007) of (fine-loamy, mixed, superactive, thermic Ustic Cal- a center row of each plot was harvested with hand ciargid) in a field that had been in native short prairie pruners, leaving a 5-cm stubble on 25 September grasses for several decades. The pH of this soil was 2006 and on 14 or 19 September 2007 for pigeon- 7.2 and N, P, and K levels were 1, 2, and 19 ppm, pea and cowpea, respectively, when the pods from respectively. There were three randomized complete the first flush of blooms began turning brown, which blocks. Individual plots were 7.62 x 3.05 m with 4 was slightly later than the harvest timing described rows spaced 0.76 m apart. Cowpea and pigeonpea by Mislevy et al. (2005), but within the range of were planted into a conventionally tilled flat seedbed harvest dates used by Rao et al.