Indianhead black lentil as green manure for wheat rotations in the Brown soil zone

Abstract

Frequent use of summerfallow (F) to reduce the water deficit associated with cereal cropping in the Canadian prairies has resulted in severe erosion and a reduction in N-supplying power of the soils. It has been suggested that it may be feasible to use annual legumes as green manure (GM) to supply the N requirements and snow trapping to enhance soil water recharge for a subsequent cereal crop. Our objective was to test the feasibility of employing this management strategy for the Brown soil zone of southwestern Saskatchewan, by comparing yields and N uptake of hard red spring wheat (W) (Triticum aestivum L.) grown in a 3-yr rotation with Indianhead black lentil (Lens culinaris Medikus) (i.e., GM-W-W) with that obtained in a monoculture wheat system (i.e., F-W-W). Both cropping systems were operated for 6 yr, from 1988 to 1993, with all phases of the rotations present each year. The results showed that grain yields of wheat after GM were generally significantly (P < 0.05) lower than those after F, primarily because the GM reduced the reserves of available spring soil water. These results occurred despite the fact that five of the six growing seasons had above average precipitation. Yields of wheat grown on stubble were unaffected by rotation. Grain N concentration was greater for wheat grown on GM partial-fallow than for wheat grown on conventional-F in the final 3 yr of the study which was due mainly to the lower wheat yields in the GM system (i.e., yield dilution). Our results suggest that, for annual legume GM to be used successfully in the Brown soil zone, producers should seed it as early as possible (late April to early May) and terminate the growth of the legume by the first week of July, even if this means foregoing some N2 fixation.