Effect nitrogen rate on yield and quality of malting barley under irrigated Mediterranean conditions

Abstract

Malting barley varieties grown in irrigated Mediterranean conditions offers higher and stable profits. It provides also grains with lower protein contents, if barley is not submitted to water stress, particularly during grain filling, like as it usually happens under rainfed conditions.

The most important criterion for grain to be classified as having malting quality, and hence to achieve a price premium, is to have a protein concentration between 9,012,0% on a dry weight basis, fact that depends mainly on nitrogen (N) fertilization levels. Moving the barley production from traditional Mediterranean dry farming to irrigation takes technicals adjustments, like rate and timing of N application.

In the Beja region, of South-Portugal, and in 2003-04, a two factorial irrigated field experiment was carried out with five N rate (0, 75, 100, 125 and 150 kg N/ha) and five application times and splitting (on sowing, sowing + tillering, sowing + stem elongation, tillering + stem elongation and sowing + tillering + stem elongation) with malting barley (variety Scarlett; Hordeum vulgare L. spp. distichum).

The results show significantly higher grain yield on the 125 and 150 kg N/ha rates and with the N application divided by sowing + tillering and sowing + tillering + stem elongation. Grain protein levels in creased with the increase in N rate, and later applications (tillering + stem elongation), but still between limits recommended for the brewing industry. Slight reduction in grain size (grading > 2,5 mm) was observed with N rate increase and applications during stem elongation, sowing + stem elongation and tillering + stem elongation.

According to our results higher N rates and later applications can be used under irrigated Mediterranean conditions when growing malting barley. Relatively to the rainfed conditions, irrigation helps to increase grain yield and improve malting quality. Such fact will has the potential to raise barley farmers profits and also provides better raw materials for portuguese breweries.