Management practices for black lentil green manure for the semi-arid Canadian prairies

Previous research with lentil (Lens culinaris Medic.) green manure in the semiarid prairies of western Canada has indicated that water use by the green manure crop often reduces grain yield of the succeeding cereal crop compared to those obtained after conventional summerfallow. In this study, we evaluated several green manure management practices that have potential to trap snow and enhance overwinter soil water recharge. These practices included: using herbicides to halt the growth of the green manure crop thus eliminating the need for soil incorporation, planting mustard (Sinapis alba L.) strips after incorporation, and leaving standing strips of non-incorporated lentil. Our results showed that none of the green manure management strategies increased wheat (Triticum aestivum L.) yield or grain protein concentration compared to wheat grown on conventional summerfallow. Leaving strips of standing lentil during bud stage incorporation provided barriers for wind erosion protection, while not decreasing wheat yield or protein content. Glyphosate or 2,4-D amine applied at bud stage of the lentil, and without soil incorporation, reduced available soil N. However, 2,4-D did not halt plant growth and water use quickly enough to avoid reducing yield of the succeeding wheat crop, while glyphosate generally halted water use more rapidly. The inability of the green manure management strategies to increase wheat yields over that obtained from conventional summerfallow was because the soil rooting zone is typically filled to capacity with water by this latter practice under the prevailing soil and climatic conditions. If green manuring is practised, early incorporation with lentil leave strips is the most promising management system. However, even with improved water management practices, green manuring did not demonstrate a consistent advantage over summerfallow, which may be required to offset the added economic costs required to enact this practice.