FIRST 18 YEARS OF A LONG-TERM CROP ROTATION STUDY IN SOUTHWESTERN SASKATCHEWAN – YIELDS, GRAIN PROTEIN, AND ECONOMIC PERFORMANCE

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Abstract
The effects of rotation length, crop sequence, and N and P fertilizers on yield, grain quality, and economic performance of 10 crop rotations in an ongoing experiment conducted on a Brown Chernozemic silty loam soil at Swift Current, Saskatchewan are discussed after the first 18 yr. When N and P fertilizers were applied based on soil tests, yields of wheat grown on fallow were similar for the 2-yr and 3-yr wheat rotations (1905 kg ha−1). Yields of wheat grown on N- and P-fertilized stubble were also similar whether grown in 3-yr or continuous rotations (1379 kg ha−1). Stubble wheat yields were unaffected by the preceding crop, except when following flax in a continuous-type rotation where it was suppressed due to moisture competition from weeds. Fertilizer N had no affect on yields of wheat grown on fallow because little N was required or applied; but yields of wheat grown on stubble were increased 7% when grown in a 3-yr rotation and 17% when grown continuously. Application of P fertilizer increased fallow and stubble wheat yields by 11–12%. In contrast to seeded area yields, total wheat production was lowest for the fallow-wheat rotation (949 kg ha−1 yr−1), intermediate for fallow-wheat-wheat (1105 kg ha−1 yr−1), and highest for wheat grown continuously (1354 kg ha−1 yr−1). Protein concentrations in wheat grown on fallow were similar in the 2-yr and 3-yr wheat rotations and were generally higher than that found in wheat grown on stubble, except when wheat was grown on flax stubble. Fallow-wheat was the most profitable rotation when wheat prices were below $130.00 t−1. At wheat prices between $130.00 and $160.00 t−1, the fallow-wheat and fallow-wheat-wheat rotations provided the highest and about equal net return; between wheat prices of $160.00 and $275.00 t−1, fallow-wheat-wheat provided the highest net return while continuous wheat provided the highest net return for wheat prices above $275.00 t−1. The cost of producing wheat was lowest for fallow-wheat ($88.00 t−1), intermediate for fallow-wheat-wheat ($94.00 t−1), and highest for continuous wheat ($138.00 t−1). Income variability and risk of financial loss decreased as the proportion of fallow in the rotation increased.Key words: Crop rotations, protein, fertilizer effects, net returns, costs, income variability