Decreasing nitrogen leaching and increasing canola forage yield in a sandy soil by application of natural zeolite

Selection of an appropriate forage species is an important first step in successful forage production. Among forage species, canola (Brassica napus L.) can be cut for hay or silage to cover certain costs of growing the crop. Because forage production is largely controlled by the environment and management, this experiment was conducted in a semiarid region of Iran during the 2006- 2007 and 2008-2009 growing seasons to investigate whether canola forage yield and its nutritive value affected by different rates of N and natural zeolite. The experimental treatments were arranged in randomized complete blocks with three replications and comprised a factorial combination of three N levels (90, 180, and 270 kg N ha^-1) and four zeolite rates (0, 3, 6, and 9 t zeolite ha^-1). The results showed that the enhanced N application from 90 to 270 kg N ha^-1 resulted in a 49% rise in forage yield for the first year and a 39% increase for the second year. The converse effects from N and zeolite yielded a significant interaction on the forage nitrogen concentration (FNC) so that the N and zeolite application enhancement led to an increase and decrease, respectively, in the FNC. The integration of the minimum N level with the maximum zeolite application generated the highest forage calcium concentration (FCC) (1.13% in dry matter). In contrast, N₂₇₀Z₀ treatment yielded the lowest FCC (0.54% in dry matter). There was a linear response between N application rate and its leaching loss whereas in the zeolite treatments, minimum N leaching was observed aft er the Z₉ treatment. A combined application of zeolite and chemical N for canola production in a poor sandy soil is recommended to ensure an acceptable forage yield and for soil protection from excess N leaching loss.