Wheat morphological defoliation regimes and regrowth potential

Dual-purpose wheat forage yield potential is linked with plant stature and growth habit. An experiment was established at Launceston, Tasmania, to study the relationship between plant structure, forage yield and crop recovery. Four wheat varieties (Tennant, Revenue, Chara and Bolac) were planted in a greenhouse. Five cutting treatments were applied at Zadoks Growth Stage (GS25) or the five-tiller stage to estimate forage yield. These included ‘Clipping’ at 50% and 75% of leaf length (LL50% and LL75%), and ‘Crash’ treatments, which were cut at the end or half way along the leaf sheath (LL100% and LS50%), and were compared to an uncut control (C0). Total dry matter was estimated by cutting all treatments to ground level at terminal spikelet (GS31). Plant height was monitored at GS25, fortnightly after GS25 and at GS31. Clipping treatments had positive effects on the plant height and biomass. Compared to the Crash and control treatments, Clipping treatments increased the height of Tennant (25% at LL50% and 17% at LL75%) and Revenue (1.8% at LL50%, 4.4% at LL75%) at GS31. Moreover, Clipping had positive effects on regrowth and increased crop height by 15% when compared to Control treatments. Forage production at GS25 and total biomass yield at GS31 were not significantly influenced by cutting treatment or variety. This study has shown that Crash treatments produced greater forage yield than Clipping, but the former generally reduces final recovery and biomass. We found that irrespective of growth habit, wheat plants defoliated at mid tillering can potentially produce more forage than unclipped plants followed by a rapid increase in plant height, provided plants are clipped above the leaf sheath.