6 31 PCentra' e ,ce P Library 7/-o0 NOV 13 1991 Agronomy Research Report AY-91-06 Growth and Nitrogen Content of Tift Blue lie of Florida Raymond N. Gallaher Professor of Agronomy, Agronomy Department, Inst. Food and Agr. Sci., University of Florida, Gainesville, FL 32611 ABSTRACT The use of lupine (Lupinus ancustifolius L.) as a cover crop, in succession double cropping, may be one solution in the quest for sustainable agricultural production systems. The objective was to determine distribution of dry matter and N in the life cycle of 'Tift Blue' lupine at 25, 50 and 100 plants m-2. Lupine planted 9 November 1990 at 25, 50 and 100 plants m-2 were grown on an Arredondo sand (Grossarenic Paleudult). Plants including roots to 0.45 m soil depth were collected eight times from 1 m2 plots from 27 to 171 days after planting (DAP). After washing, the samples were separated into plant parts, dried, weighed, ground and analyzed for N. Dry matter and N accumulation patterns were similar for the 50 and 100 plants m2, and both accumulated about twice as much dry matter and N as the 25 plants m'2. Highest dry matter and N content for the 100 plants m'2 were 2134 and 35.96 g m"2, respectively at 147 DAP. INTRODUCTION Winter legumes are used for cover crops, protein sources, mulches for succeeding no-tillage crops, rotations for pest management and for improving soil fertility. When grown as a cover crop, lupine (Lupinus anqustifolius L.) can be sacrificed for the N and conservation benefits of the succeeding double crops such as corn (Zea mays L.) or grain sorghum (Sorghum bicolor L. Moench) (Gallaher and Eylands, 1985). Such a cover crop can serve as a mulch to conserve soil moisture if the soil has moisture to conserve (Gallaher, 1977). A mulch will aid in reducing erosion, moderate soil temperature, aid in competition against weed growth and conserve soil moisture from natural rainfall or irrigation. It may also furnish N and other recycled nutrients (Gallaher, 1986) and in some rotations may also be useful in controlling pests, such as breaking the cycle of nematodes, etc. Cover crops can be killed before or after the succeeding multiple crop is planted using no- tillage management (Gallaher, 1980). The objective was to determine distribution of dry matter and N in the life cycle of 'Tift Blue' lupine at 25, 50 and 100 plants m2.