Effects of irrigating forage turnips, Brassica rapa var. rapa, during different periods of vegetative growth. 1. Turnip yields, yield components and growth rates

Abstract

The effects of applying irrigation to spring sown forage turnips, Brassica rapa var. rapa cv. Barkant, during four stages of vegetative growth on yields, yield components and growth rates, were investigated in two field experiments in north-west Tasmania during the 1999–2000 and 2000–01 spring–summer seasons as a basis for developing irrigation strategies for turnip that could improve their efficiency of water use. Increases in dry matter yield in response to irrigating during the four consecutive periods of vegetative growth were additive for all treatment periods and harvest times: the yield increases to irrigation during any period were independent of prior or subsequent levels of irrigation. Consequently, yield increases that are foregone because of the onset of moisture deficits during an earlier period cannot be recovered in a later period: there is no compensatory growth. The results also show that moisture deficits that restrict yields in a previous treatment period do not restrict yield response to irrigation in later periods: the turnip crop appears to respond immediately to the removal of a water stress.