Effects of long-term tillage, crop rotation and nitrogen fertilization on bread-making quality of hard red spring wheat

The effect of tillage system, crop rotation and nitrogen (N) fertilization rates on the quality of hard red spring wheat (Triticum aestivum L.) was studied over a 6-year period under rainfed Mediterranean conditions. Grain yield, test weight, protein content and alveogram parameters (W: alveogram index; P: dough tenacity; L: dough extensibility; P/L: tenacity-extensibility ratio; G: swelling index) were analyzed. Tillage treatments included no tillage (NT) and conventional tillage (CT). Crop rotations were wheat-sunflower (Helianthus annuus L.) (WS), wheat-chickpea (Cicer arietinum L.) (WCP), wheat-faba bean (Vicia faba L.) (WFB), wheat-fallow (WF) and continuous wheat (CW). Nitrogen fertilizer rates were 50, 100 and 150 kg N ha(-1) on a Vertisol (Typic Haploxerert). A split-split plot design with four replications was used. Weather conditions over the study years strongly influenced wheat yield and quality. Test weights rose considerably with yield and increased rainfall during the filling period, and fell slightly as N rates increased. Grain protein content increased with rainfall in the month of May (when grain protein accumulation occurs) up to a maximum of 80 mm. Grain protein content peaked at average mean temperatures of around 26-27 degreesC. Protein content and alveogram parameter also improved under CT, following a prior legume crop and with rising N fertilizer rates. Alveogram parameters rose with protein content, although the P/L ratio showed greater imbalance. N fertilizer proved to be a key factor in determining bread-making quality, and the best strategy available to the farmer for optimizing wheat quality. However, the influence of weather conditions and soil residual N should be borne in mind when deciding on the additional fertilizer N to be used as a top dressing with a view to increasing yield and, particularly, enhancing wheat protein content and bread-making quality. (C) 2001 Elsevier Science B.V. All rights reserved.