Chickpea response to tillage and soil residual nitrogen in a continuous rotation with wheat -: II.: Soil nitrate, N uptake and influence on wheat yield

A field study was conducted in Cordoba (Spain) on a Vertisol between 1996 and 2001 to determine the effects of tillage system and residual N on spring chickpea N uptake, soil nitrate content and wheat yield in a wheat-chickpea rotation under rainfed Mediterranean conditions. Tillage treatments were no-tillage and conventional tillage. Nitrogen fertilizer rates were 0, 50, 100 and 150 kg ha(-1) applied only to wheat. The weather had a marked influence on chickpea N uptake. Total N uptake ranged from 60 to 90 kg ha(-1) of which between 42 and 82% was removed by the seed. Total N uptake and seed N uptake were correlated with rainfall during the preceding fallow period and during the flowering and seed-filling period. Straw N uptake decreased with the increase of seed yield. The chickpea crop leaves poor above-ground N residues due to a high N harvest index. Seed N concentration ranged from 3.6 to 4.1%, while straw N levels ranged from 0.8 to 1.4%. The mean N utilization efficiency (NU,E) was 28.4 kg kg(-1) (ranging from 11.4 to 22.8) and N harvest index (NHI) was 68% (ranging from 45 to 82%). Chickpea N uptake was directly related to soil nitrate content; it was greater under conventional tillage than under no-tillage, and increased when higher N fertilizer rates were applied to the preceding wheat crop. Overall, the chickpea crop seems incapable of meeting N demands by fixation and does not even supply an equivalent quantity of 50 kg ha(-1) of N fertilizer to the following wheat crop. (C) 2004 Elsevier B.V. All rights reserved.