EFFECT OF PHOSPHORUS LEVEL AND DEFOLIATION DATE ON SEED PRODUCTION OF STYLO (STYLOSANTHES GUIANENSIS CV. SCHOFIELD) IN THE SOUTHERN GUINEA SAVANNA ZONE OF NIGERIA

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EFFECT OF PHOSPHORUS LEVEL AND DEFOLIATION DATE ON SEED PRODUCTION OF STYLO (STYLOSANTHES GUIANENSIS CV. SCHOFIELD) IN THE SOUTHERN GUINEA SAVANNA ZONE OF NIGERIA

Abstract:

During 1979-1981, three experiments were conducted to i n v e s t i g a t e the effect of phosphorus and d e f o l i a t i o n on the growth, seed production and percentage seed germination of S. guianensis cv. Schofield, using a s p l i t plot design. 1. Experiment I considered the effect of five phosphorus levels (0, 30, 60, 90 and 120 kg P/ha) on seedling emergence, dry matter (DM) yield, herbage chemical composition and seed yield of S. guianensis. Counting and cutting dates constituted the sub-plots for seedling emergence and DM yield while seed harvesting date formed the sub-plot for chemical composition and seed yield. 2. In experiment II the effect of five defoliation treatments (no defoliation compared with defoliation on 25/7, 25/8, 25/9 and 25/10/79 = Main plot) on seed yield of S. guianensis regrowth was sought. The sub-plot treatment was different seed harvesting dates. 3. Experiment III examined the effect of five level of phosphorus on percent germination of S. guianensis seed harvested on different dates from 3/l/81 to 14/3/81. The number of seedlings emerging increased progressively with increasing level of P. By the 14th day of sowing, approximately 75 percent of the t o t a l seedlings counted on day 21 had emerged. DM yield increased from I3.5t/ha without P to 15t/ha with 120kg P/ha in the year of establishment. The corresponding DM yield values two years after (1981) in response to residual P were 14t and 19.2t/ha respectively. Percentage crude protein in tops rose with additional P and declined with delay in harvesting as hay. Crude fibre, ether extract, ash and nitrogen free extract percentage were not consistent in respect of either P or date of cutting. Seed yield in the first year (1979/80) maximised at 60 kg p/ha and tended to decline at higher P doses. In 1980/81 however, seed yield response to residual P reflected the level of P applied in the 1979 growing season. Late January/mid February appeared the most suitable for harvesting S. guianensis cv. Schofield for seed. On this basis, and using modest P (30 to 60 kg P/ha), standing seed yield varied from 325 to 434 kg/ha for the 1979/80 crop. The corresponding total seed yield values were 387 to 507 kg/ha and 346 to 445 kg/ha, respectively. Seed yield declined considerably after mid-Ibbruary due to severe pod shedding (standing seed) and intensified seed gathering by harvester ants (fallen seed). Defoliation between late July and late September resulted in the highest seed yield when seed harvesting occurred in mid- February. The data suggested that S. guianensis cv. Schofield regrowth could be for conservation up to late September without necessarily causing any observable reduction in subsequent total seed yield. P had no effect on seed germination. The number of fallen seed germinating significantly exceeded that of standing seed.

EFFECT OF PHOSPHORUS LEVEL AND DEFOLIATION DATE ON SEED PRODUCTION OF STYLO (STYLOSANTHES GUIANENSIS CV. SCHOFIELD) IN THE SOUTHERN GUINEA SAVANNA ZONE OF NIGERIA

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