Experimental studies on seed production tropical grasses in Kenya. 6. The effect of harvest date on seed yield in varieties of Setaria sphacelata, Chloris gayana and Panicum coloratum.

Setaria sphacelata cv. Nandi I and Nandi III, Chloris gayana cv. Mbarara, Masaba and Pokot, and Panicum coloratum cv. Solai were grown for seed and harvested on a range of dates beginning 3-4 weeks after initial head emergence (defined as 5-10 heads/m2). Harvesting date was not very critical, and harvesting could normally be spread over 1-2 weeks. The interval between initial heading and optimum harvest date was normally 6-7 weeks. In most crops considerable shedding of spikelets (up to 30-50% in P. coloratum, rather less in the other 2 species) could be tolerated before yield of pure germinating seed fell with delay in harvesting. It was suggested that most of the spikelets which were shed early were empty. Cultivars which headed early produced nearly twice as much seed as those which headed late. (Abstract retrieved from CAB Abstracts by CABI’s permission

Experimental studies on seed production of tropical grasses in Kenya. 5. The effect of time of nitrogen top dressing on seed crops of Setaria sphacelata cv. Nandi.

Effects of date of applying top-dressings of N to early-season and late-season seed crops of Setaria sphacelata cv. Nandi were studied in 4 trials in 1967-71. Highest seed yields were obtained when N was applied as soon as possible after the onset of the rainy season; a delay of 4 weeks reduced yields of pure germinating seed by >60%. Total yields of herbage DM and number of heads were also reduced, but to a lesser extent; the main adverse effect was on seed set/head. In late-season crops, applying N 2 weeks after the earliest possible date proved beneficial in 2 out of 3 years. (Abstract retrieved from CAB Abstracts by CABI’s permission

Experimental studies on seed production of tropical grasses in Kenya. 4. The effect of fertilizer and planting density on Chloris gayana cv. Mbarara.

Rhodes grass sown broadcast or in rows 25-100 cm apart at 0.2-1.8 kg pure germinable seed/ha was given 0-80 kg seedbed P2O5 and 0-200 kg N/ha for each seed crop. Yields of DM in the establishment year were significantly higher at high seed rates and close spacing, whereas yields of clean seed were decreased from 145 kg/ha (50-cm rows) at the lowest seed rate to 110 kg/ha at the highest. Seed yields were highest, 160 kg/ha, from broadcast sowings at 1 kg/ha. Yields of pure germinable seed were not significantly affected by treatment. In 6 seed crops taken after establishment, the only factor of importance for seed yield was N; yields of pure germinable seed increased from 6.2 kg/ha without N to 36.7-41.0 kg/ha at 100 kg N/ha and 41.2-43.2 kg/ha at 150 kg N/ha. DM yields from these 6 crops were higher at the wider row spacings. Increased N and wider spacing accelerated the onset of heading. (Abstract retrieved from CAB Abstracts by CABI’s permission

Experimental studies on seed production of tropical grasses in Kenya. 1. General introduction and analysis of problems.

Problems in seed production of Setaria sphacelata (2 cv.), Chloris gayana (3 cv.), Panicum coloration, P. maximum, Brachiaria ruziziensis and Melinis minutiflora are discussed. Low yields and quality were due to varying combinations of prolonged heading season per plant and per cultivar, prolonged flowering within a given head, low seed set, low number of fertile tillers, low seed retention, disease and bird damage. Actual yields were only about 5% of potential yields.-R.B. (Abstract retrieved from CAB Abstracts by CABI’s permission

Herbage quality in Rhodes grass (Chloris gayana Kunth). 2. Intra-variety variation in yield and digestibility of plants of similar heading date.

20 clones of similar heading date and selected from within Rhodes grass cv. Masaba were assessed at 3, 6 and 9 wk of regrowth. Lengthening the period of regrowth increased yield of DM and yield of DOM, but decreased digestibility in vitro of leaf, stem and whole-sward samples and leaf:stem ratios. Clonal effects were also significant for these characters except for leaf digestibility and leaf:stem ratio. No significant clone X regrowth period interactions were observed. Stem and leaf digestibility fell by 0.20 and 0.17 units daily, resp., while leaf:stem ratio dropped to 1.1 at 9 wk regrowth which coincided with initial heading. At this stage whole sward digestibility had fallen to 53, at a rate of 0.22/day. Leaf digestibility was always higher than that of stem. Clones differed significantly in digestibility showing a 5-unit range which had no relation to leaf:stem ratios. The 7 clones best in digestibility were among the 9 lowest in herbage yield. The ranking for yield of DOM did not differ from that for yield of DM, which showed a range of 1.38-2.45 t/ha. It is concluded that potential genetic gain in digestibility and leaf:stem ratio is offset by a corresponding decline in herbage yield. (Abstract retrieved from CAB Abstracts by CABI’s permission

Experimental studies on seed production of tropical grasses in Kenya 7. The breeding for improved seed and herbage productivity.

The history and characteristics of the Kitale varieties of Setaria, Chloris, Panicum and Brachiaria are described, as are seed multiplication practices and current breeding work. (Abstract retrieved from CAB Abstracts by CABI’s permission

On the seed production of tropical grasses in Kenya

The small amount of viable seed that can be harvested from tropical ley grasses such as Chloris gayana, Setaria sphacelata and Panicum spp. is largely due to the wide range in maturity between different heads and in maturity between seeds in any head. Ripe seed is also liable to shed. Adequate and timely top dressing with nitrogen, close row width and careful choice of harvest date increased seed yield either directly or by synchronizing ripening. There was considerable variation within and between varieties in seed yield characteristics: heading date, head number and seed setting, which all displayed high heritability. Heading date and head number were closely correlated with vigour of regrowth. Varieties could well be improved simultaneously for seed and herbage productivity

Nitrogênio e época de colheita nos componentes da produtividade de forragem e sementes de capim-mombaça

O objetivo deste trabalho foi avaliar o efeito de doses de nitrogênio e de épocas de colheita de sementes sobre componentes de produtividade de forragem e sementes de capim-mombaça (Panicum maximum cultivar Mombaça). Os tratamentos foram constituídos das doses 0, 75, 150, 225 e 300 kg ha-1 de N e da colheita das sementes aos 8 e 14 dias após a antese. Utilizou-se o delineamento em blocos ao acaso em parcelas subdivididas, com quatro repetições. A produtividade de forragem e de lâmina foliar foi afetada positiva e linearmente pelas doses de N. Os caracteres densidade de perfilhos com panículas, número de sementes aparentes e de sementes puras por panícula, e produtividade de sementes aparentes e puras foram afetados pela interação entre doses de N e época de colheita. Observou-se correlação positiva do número de sementes por panícula e do peso de mil sementes com as produtividades de sementes aparentes e puras. As maiores produtividades de sementes aparentes e puras - 89,1 e 28,2 kg ha-1, respectivamente - foram obtidas com as doses de 241,2 e 250,0 kg ha-1 de N, aos oito dias após a antese