Alternatives to summerfallow and subsequent wheat and barley yield on a dark brown soil

A number of alternative options to summerfallow are feasible on the Dark Brown soils of the Canadian prairies. These include recropping to cereal or pulse crops, as well as use of summerfallow substitute crops, such as legume green manures. The objective of this study was to evaluate these options for their impact on the productivity of subsequent crops. Green-manure lentil (Lens culinaris Medic.), incorporated at either the bud or full-bloom stage of growth, field pea (Pisum sativum L.), grain lentil, and wheat (Triticum aestivum L.) grown as grain were compared with conventional summerfallow for their impact on yield of a succeeding wheat crop and of barley (Hordeum vulgare L.) grown the year after wheat on a Dark Brown Chernozemic soil at Scott, Saskatchewan. During the 5-yr period, 1984-1988, above-ground dry-matter production of green-manure lentil averaged 1500 kg hal at the bud stage of growth but more than doubled to 3170 kg ha(-1), by full bloom. Grain yield of field pea averaged 1470 kg ha(-1), while that of grain lentil, unfertilized wheat, and N-fertilized wheat averaged 1220, 1290 and 1490 kg ha(-1), respectively. Considerable year-to-year yield variation occurred with all crops, variability being greatest for lentil. Yield of wheat grown after lentil green manure was similar to yield of wheat on summerfallow (2340 kg ha(-1)) during each of the 5 yr for both early (2360 kg ha(-1)) and late (2250 kg ha(-1)) incorporation. Wheat yield after pea (2210 kg ha(-1)) or grain lentil (2080 kg ha(-1)) was reduced in 1987, but it was equal to wheat yield after summerfallow during the remaining 4 yr. Yield of wheat on wheat stubble, whether fertilized with N (1830 kg ha(-1)) or not (1610 kg ha(-1)), was generally lower than on summerfallow. Yield of barley grown the following year was generally unaffected by summerfallow or summerfallow substitute treatments. The higher value and similar productivity of pea and grain lentil, compared with wheat, combined with their favourable impact on subsequent wheat yield, should make these crops attractive alternatives to summerfallow. On fields unsuited to pea or grain lentil production, lentil green manures may be a suitable alternative to summerfallow because they should reduce soil degradation, although lentil green manures leave little residue to protect against soil erosion where thorough incorporation is practised. Summerfallow or green manure incorporated early or late generally resulted in greater available soil water and N for a succeeding crop than did grain lentil, pea or wheat.