Effect of rate and timing of nitrogen fertilizer application on the proportion of ear, the digestibility of straw constituent and the quality of whole crop barley at different stages of maturity

Abstract

In each of two successive years, spring barley ( Hordeum vulgare L.) was fertilized with 90, 130 and 170 kg nitrogen (N) ha −1. For the higher application rates, N was either given entirely in the seedbed (i.e. single application), or the application was split, with most being given at sowing and 40 kg N ha −1 added when the crop reached the initial ear emergence stage of development (i.e. split application). Assessments were made of the proportion of ear and the quality of the whole crop and its straw fraction with advancing maturity. Raising the quantity of fertilizer N led to greater lignification and a reduction in the in vitro digestibility of organic matter (IVOMD) in the straw fraction. Responses were comparable at all stages of maturity, but differed between the two experiments, probably because of interactions with climatic factors. Compared with the single application, the split application approach reduced lignification and improved IVOMD. The proportion of ear in the barley crop was slightly reduced by higher N applications. In contrast, split applications had a small, positive, though non-significant, effect on this parameter. Increased lignification as well as a reduced proportion of ear may combine to depress the IVOMD of the whole crop barley in response to heavier N fertilization. By delaying the application of part of the N until the initial ear emergence stage the effects were partly alleviated.