Comparisons of Forage Yield and Quality of Legume-Interseeded and Nitrogen-Fertilized Rye.

<>Interseeding legumes with pasture grasses may increase forage yield and provide fixed nitrogen (N) for use by the pasture grass component. The objective of this study was to compare forage yield and quality of rye (Secale cereal L.) pasture interseeded with legumes with pasture grass receiving inorganic N fertilizer. Replicated field-plot experiments were established in September 2007 and 2008 and evaluated for fall and spring forage production on loam and sandy soils in southern Oklahoma. Treatments included (1) rye interseeded with hairy vetch (Vicia villosa Roth), (2) rye interseeded with hairy vetch and cowpea [Vigna unguiculata (L.) Walp.], (3) rye interseeded with arrowleaf clover (Trifolium vesiculosum Savi), (4) rye interseeded with arrowleaf clover and cowpea, and (5, 6, 7, and 8) represents rye fertilized with 0, 56, 112, and 168 kg N/ha.  Each plot in each year of the study were harvested multiple times between October and April. 

Rye receiving 112 or 168 kg N/ha produced the highest total annual forage (> 8000 kg/ha). Rye receiving 56 kg/ha produced 7400 kg/ha, yields comparable to that from rye interseeded with vetch. All pastures with interseeded clover or a cowpea component produced yields similar to that of the non-fertilized control. There was a trend for increased yields with N fertilizer during all harvest periods, with the greatest yields realized in February. Also, yield from the rye intersteeded with vetch were greatest in February, and were about 1000 kg/ha greater than yields obtained with a cowpea component.

Nitrogen fertilizer at ≥ 112 kg N/ha increased crude protein (CP), total digestible nutrient (TDN) and in vitro dry matter digestibility (IVDMD), and decreased Acid detergent fiber (ADF) and neutral detergent fiber (NDF).  Interseeded rye-vetch mixtures had CP, ADF, NDF, TDN, IVDMD content, similar to that of forage fertilized with 56 kg N/ha, but higher than that of forage with a cowpea component. Nitrogen fertilizer application significantly increased CP content in February and March compared to other harvest periods. Crude protein content  was highest in October and lowest in April with no significant difference among treatments. Forage quality—via 1.5 to 2-fold increases in ADF and NDF—declined substantially from October through April.  Forage interseeded vetch had concentrations of NDF and ADF similar to that of rye receiving ≥ 112 kg N/ha.  Forage P, Ca, and Mg increased with N fertilization rates and rye interseeded vetch had a relatively high Ca and Mg than that interseeded clovers.

In general, N fertilized rye produced more forage of high quality than rye interseeded legumes.