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The effects on bread-making quality of crop rotation, fertilizers and manure treatments were evaluated in a long term experiment in which the combinations of organic manure, mineral nitrogen, phosphorus and potassium fertilizers were applied to three crop rotations for a total of 33 different treatments. Protein concentration evaluated for 12 years varied from 10.0 per cent to 12.8 per cent with years and from 10.70 per cent to 13.21 per cent among treatments. The highest grain yields were obtained in the two-year (wheat-maize) or nine-year (wheat-maizelucerne) rotations, coupled with a great variability for quality, as evaluated with the Chopin alveograph. Potassium fertilizer did not affect yield or quality, while positive effects of phosphorus were evident only after continuous cropping with wheat. When wheat was grown continuously, the application of nitrogen fertilizer gave grain of optimum quality but, even in combination with the highest rate of manure, did not raise the yield to the levels achieved by the 2 or 9 year rotations. In the wheat-maize rotation, maximum yield and quality was achieved with the highest rate of fertilizers even in the absence of manure. In the rotation that included lucerne, maximum yield was obtained with the lowest rate of fertilizers but, to optimize the quality, it appeared necessary to apply the highest rate of nitrogen (200 kg N ha−1). |
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