Monday, November 13, 2006
105-1
Radiation Use Efficiency in Dual Winter Small Grain - Forage Production Systems.
Jeremy W. Singer1, Tom J. Sauer1, Brock C. Blaser2, and David W. Meek1. (1) USDA-ARS National Soil Tilth Lab, 2150 Pammel Dr, Ames, IA 50011, (2) Iowa State Univ, 4130 Lincoln Swing #34, Ames, IA 50014
Small grain production systems in the northern USA are inefficient in respect to annual photosynthetically active radiation (PAR) capture. Our objectives were to determine radiation use efficiency (RUE) in winter wheat (Triticum aestivum L.) and triticale (x Triticosecale Wittmack) at different plant densities and RUE of interseeded red clover (Trifolium pratense L.) during two growth periods after small grain harvest. During the linear phase of small grain growth (Zadoks stages GS 30 to 80) RUE averaged 3.50 g MJ-1 for wheat and 3.21 for triticale in 2004 and 6.37 and 5.82 for wheat and triticale in 2006. Small grain density treatments inversely affected red clover RUE during the first growth period in 2004, when the 99, 198 and 395 seeds m-2 rates in wheat were described by y = 2.34PAR, y = 96.3 + 1.59PAR, and y = 1.59PAR. For triticale, the equations were y = 1.46PAR, y = 1.89PAR, and y = 1.46PAR for the 99, 198, and 395 seeding rates. During the second clover growth period in 2004, no density dependence was detected following wheat (y = 5.83 + 0.55PAR). Following triticale, RUE was 0.45 g MJ-1 for all seeding rates, but the 99 seeding rate had a positive intercept. Following small grain harvest until day of year 277 in 2004, red clover intercepted from 42 to 67% of the 719 MJ m-2 available energy. Interseeding red clover into winter small grains increases seasonal radiation capture and provides multiple benefits to the agroecosystem.