HARVESTING LOSSES OF SPRING WHEAT IN WINDROWER COMBINE AND DIRECT COMBINE HARVESTING SYSTEMS

Harvest loss of cereal crops has been reported to be reduced by windrow-drying prior to combing compared to direct combining, but few comparisons of the 2 systems have been made. Field studies [Saskatchewan, Canada] were conducted [T. aestivum and T. turgidum var. turgidum] cultivars of varying shattering resistance in direct combine and windrower/combine harvesting systems on a Swinton loam soil (Aridic Haploboroll). Cutting treatments were initiated when kernel water concentration was about 670 g water per kg kernel dry weight and continued for at least 2 wk after kernel water concentration reached 170 g kg-1. Natural shattering losses and cutting losses were measured at each cut; combine pick-up losses were measured when the windrows were combined. Cutting and pickup losses did not change with cutting time and there was no consistent variation among cultivars. Cutting losses ranged from 0.75 to 3.03 g m-2, pick-up losses ranged from -0.10 to 0.98 g m-2. Natural shattering losses varied with cultivar and year; cumulative loss ranged from a low of 4 to a high of 27 g m-2 over a period to some 2 wk after kernel water concentration reached 170 g kg-1. Harvesting losses were similar for the two harvesting systems for cultivars resistant to shattering, but greater for the direct combine than for the windrower/combine system for cultivars susceptible to shattering. An earlier start to direct combining (at kernel water concentrations of 170 to 250 g kg-1) narrowed the difference between the systems for cultivars susceptible to shattering as did delayed windrowing.