Litterfall and seasonal pattern of nutrient accretions of Dactyladenia barteria, a bush fallow species, were studied at Ozala, Nigeria for 52 weeks (26 May 1985 to 24 May 1986). Total litterfall was continuous throughout the year, with a peak from December to May, corresponding to the dry and early rainy season. The dry season (November–March) had 65.5% of the total leaf litterfall. The mean total litterfall of the leaf, flower/fruit and twig litter component was 977.2±6.7 g m−2. Litterfall correlated positively with maximum air temperature but negatively with rainfall. Except for K, there were no significant seasonal variations in the mean concentrations of N, P, Na, Ca, Mg, organic C and C:N ratios in the D. barteria leaf litter. The contributions of each litter part to the total nutrient input at Ozala in order of magnitude were as follows: leaf, flower/fruit, twig litter. The study stresses the great potentials of this species for alley cropping/farming.

Decomposition of the leaf litter of Acioa barteri, Centrosema pubescens and Chromolaena odorata (Syn. Eupatorium odorata) was studied in the laboratory using the litterbag technique. The same litterbag technique was used for the leaf litter decomposition of A. barteri and Centrosema pubescens at Ozala and Nsukka, respectively. Carbon dioxide evolution for the three species was studied in the laboratory for 52 weeks. Acioa barteri and Centrosema pubescens had turnover coefficients (kl) of 1.4 and 1.5 and also litter half-lives of 25.1 and 23.4 weeks, respectively. In the laboratory, Chromolaena odorata and Centrosema pubescens attained 100% decomposition at Weeks 8 and 16 respectively, while A. barteri had 85.3% at Week 48. However, under field conditions at Week 48, Centrosema pubescens attained 85% weight loss while A. barteri had 86.7%, a trend similar to its leaf litter decomposition value under field conditions. Carbon dioxide evolution for all three species was significantly greater during the first 4 weeks and thereafter declined steadily. The control (top soil only), however, had the least mean periodic CO2 evolution followed by soil + A. barteri.

Nutrient accretion to the soil is primarily through litterfall, litter decomposition and precipitation (rainfall, throughfall and stemflow). Although N, P and Ca accrue to the soil mainly through litterfall with some net - throughfall and rainfall contributions, net - throughfall, however, accounts for most of K and Mg inputs to the soil [Parker, 1983]. Nutrients in litterfall are more slowly released into the soil from organic matter than those from throughfall which are either easily absorbed by plant or quickly leached away in the soil [Gosz et al., 1976; Parker, 1983]. Rapid decomposition of plant litter at the onset of the rainy season, however, usually enhances major increases in nutrient accumulation over a relatively short period [Swift et al., 1981].In view of the importance of nutrient dynamics in the tropics, studies were undertaken to quantify the turn over from litterfall and throughfall under Acioa barteri stands in a bush fallow at Ozala, Nigeria. The results of such studies would, therefore, stress the need for the present resurgent interest in the biologically enriched bushfallow system of agroforestry and its variant, alley cropping, largely because of the scarcity and high cost of inorganic fertilizers in Nigeria and also because of the stability of these systems against soil erosion. This paper, therefore, summarizes the results of the nutrient inputs within this agroecosystem.

The nutrient requirements of filegrass ( Anthephora ampulacea , Stapf and Hubb), a potential pasture species, is hardly known. A greenhouse experiment was conducted to study the effects of applied N, P, and K fertilizers on its herbage yield and quality. Four rates of N (0, 100, 200 and 300 kg N/ha −1 as ammonium sulfate); three rates of P (0, 33, and 66 kg P ha −1 as single superphosphate); and three rates of K (0, 62, and 124 kg K ha −1 as muriate of potash) were applied in solution in all possible treatment combinations (36 treatments). Plants were first harvested when 50% of the primary tillers were at early anthesis, A second harvest was made after 4 weeks of regrowth. Fertilizer application at 100 kg N/ha −1 rate at least doubled filegrass yield (7.4 vs. 14.8 g pot −1 for 0 vs. 100 kg N ha −1 rates). Higher rates of N application gave further significant yield increases (19.4 and 19.9 g pot −1 for 200 and 300 kg N ha −1 , respectively). For the regrowth harvest, yields differed significantly such that 0 < 100 < 200 < 300 kg N ha −1 . Filegrass response to applied N is represented by the following regression equations Y = 9.2 + 0.05 × (for first harvest) and Y = 1.39 + 0.018 × (for second harvest). Applied P and K fertilizers did not significantly affect the dry matter yields and concentration of other nutrients in both the leaf and stem fractions. Applied N at 100 kg ha −1 rate increased N concentration of the leaf fraction but decreased P, Ca, and Mg of the leaf. Higher N rates, however, increased these nutrients in the leaf blade. Nitrogen application, at all rates, increased the stem concentrations of N from 0.49 to 1.20; P from 0.16 to 0.26; K from 0.87 to 1.12; Ca from 0.11 to 0.56 and Mg from 0.06 to 0.19% on dry matter basis. The dry matter digestibility (DMD) values for both leaf and stem fractions were relatively close (62.8 and 53.4%, respectively). The DMD of each fraction was increased by N application from 45.6 to 65.7 in the leaf and stem when the rate was increased from 0 to 300 kg N ha −1 . These results were discussed in terms of herbage production and livestock requirements.

AbstractA method for disposing of rice‐mill wastes is needed to avoid their pollution and fire‐hazard potential. Two greenhouse experiments were conducted to determine the effects of rice shavings and rice husks on forage‐corn (Zea mays L.) production in two soils.In Experiment I, rice (Oryza sativa L.) shavings were applied at rates of 0, 75 000, and 150 000 kg/ha with or without additions of nitrogen (N), nitrogen and potassium (NK), nitrogen, phosphorus, and potassium (NPK), or poultry droppings (PD). The residual effects of these treatments, involving in some cases a further application of N, were also evaluated.Corn top and root yields were at least doubled with rice shavings application. Highest yields were obtained with rice shavings plus NPK or PD applied at a rate equivalent to 100 kg/ha. Additions of either N or K only did not affect yield. Although yields differed on the two soils, the responses to treatments were similar.In Experiment II, rice husks and shavings were compared in the presence or absence of N and NPK fertilizers. In the absence of fertilizer, there were no yield differences between the two; otherwise, rice husks at 150 000 kg/ha were superior to rice shavings.These results suggest that under the conditions of this study, the rice waste‐soil system had enough N to support an initial cropping to corn, and P was the major limiting nutrient. Poultry droppings were as good as any of the feritlizer combinations used. Although not investigated, a significant component in the yield improvement may have resulted from the effects of these wastes on the soils' physical properties. The use of these wastes for corn production would, in addition to increasing yield, eliminate waste disposal problems without creating environmental hazards.

AbstractDuring the annual dry season (October to March) in much of the tropics, supply of herbage for the livestock is limited. Hay and silage making are usual methods of conserving herbage but these methods are capital intensive and easily out of reach of the tropical pastoralist. Therefore, other methods of conserving herbage have to be evolved. In this study, stockpiling was used to conserve herbage. The main. objective of the experiment was to study the effects of four stockpiling periods on dry matter yields. Also, residual effects of management on the sward's productivity were assessed. Three forage species that are extensively used in grassland agriculture in southern Nigeria were stockpiled in 1977 and 1978 to provide dry‐season feed. The species were stargrass (Cynodon nlemfuënsis Vanderyst), elephant grass (Pennisetum purpureum Schumach.) and guineagrass (Panicum maximum Jacq). The four stockpiling periods were from either June, July, August, or September to November of each of the 2 years. Yield and quality of herbage from the poststockpiling cuts were estimated in December 1977, February and December 1978, and February 1979. On 15 May 1978 and 1979 residual effects of both the stockpiling and the subsequent post‐stockpiling dry season cuts on the swards performance were assessed. For the 2 year period, dry matter yields averaged over all three species were highest (7,330 kg/ha) and lowest (2,100 kg/ha) from the July and September stockpilings, respectively. The species varied in dry matter yields, and in the stockpiling period that gave the highest yields. Stargrass attained its highest yield from June stockpiling while the other two species were highest from July stockpiling. Elephant grass had a significantly higher dry matter yield (5,500 kg/ha) than either stargrass (4,370 kg/ha) or guineagrass (4,360 kg/ha). Yields from post‐stockpiling herbage cuts in December and February were low (390 to 1,800 kg/ha). However, the quality was relatively high for a herbage at this season—percentage crude protein (CP%) = 4.3 to 10.8; acid detergent fiber (ADF%) = 39.8 to 43.8; and total ash percentage = 4.7 to 12.4. There were no significant residual effects of stockpiling periods on the dry matter yields of herbage harvested early in the following season. These results suggest that stockpiling is an attainable method of providing good quality herbage during the dry season in the tropics. However, more studies involving different aspects of its management will still be required.

The effects of seasons on size, number and area of the dung deposited on a grazed paddock were examined. Rate of dung breakdown, herbage fouling, and rejection were also investigated. Significant seasonal differences were found in number, size, area of dung and in proportion of paddock fouled per grazing such that these values were higher in wet than in dry season. A higher breakdown rate was obtained in the dry season when the termites were the main degradation agents than in the wet season when the dung was degraded mainly by the copriphilous fungi. The herd rejected the fouled herbage for a longer period during wet season than during the dry season. Two breakdown patterns for the dry season (depending on the presence of termites in the ecosystem) were suggested. Herbage rejection was discussed in relation to animal production and range improvement. In the tropics, use of synthetic fertilizer for herbage production is an infrequent practice. The pasture, for its nutrient supplies, has to depend on both the crop’s inherent ability to fix nitrogen and on nutrient recycling. Where the pasture is grazed, the latter process then includes dung voiding and breakdown. However, in many parts of the tropics, including the derived Savannah zone of Nigeria, few studies have been conducted to assess the role of the dung in maintaining the ecosystem’s nutrient cycle. In the temperature latitudes, the dung has been shown to be affected by both climatic and biotic factors. Dung voided in summer disappeared more slowly than that voided in winter (MacDiarmid and Watkin 1972). Arthropods, fungi, and bacteria have all been implicated in dung breakdown. Castle and MacDaid (1972) reported rejection of the herbage around the pats up to one year after they were voided. In the present experiments, the influence of the seasons on size, number, and rate of breakdown of the dung voided was examined. Also, the organisms involved in the breakdown and the behaviour of the grazing animals to the dung in the paddock were investigated.

AbstractLivestock production potentials in tropical areas are often unattainable because of limited availability of good quality herbage. Rates of herbage growth and lignification are high resulting in production of poor quality herbage during the rainy season and severe herbage scarcity during the dry season. Factors other than depleted soil moisture, which may contribute to the decreased production in the following dry season, needed investigation. This experiment, therefore, studied the influence which harvesting interval used during the rainy season may have on dry−season herbage production of three well−adapted herbage species.Two−year−old swards of guinea (Panicum maximum, Jacq.), elephant (Pennisetum purpureum, Schum.), and star (Cynodon nlemfnensis, Vanderyst) grass were used in the experiment from March 1977 to March 1979. The grasses were grown on fine, sandy loam soil of the Nipologuri series (an chesol). Plots were mowed either every 3, 4, 5, 6, 8, or 10 weeks between 10 March and 27 October each year. Beginning the end of November until the end of March the following year, each plot was mowed at 4−week intervals irrespective of the rainy−season management. Results showed that infrequent rainy−season harvesting encouraged dry−season dry matter production. Mean dry matter yields were 1,022, 1,103, 1,108, 1,119, 1,171, and 1,189 kg/ha/month for 3, 4, 5, 6, 8, and 10−week intervals, respectively. Quality of the dry−season herbage was largely unaffected by the rainy−season management. Significant species differences existed with star grass being inferior to the others (cf. 10.0, 10.6, and 6.2% CP for elephant, guinea, and star grass, respectively). Quality decreased with the advance of the dry season, for example, 13.8 vs. 7.9; 29.2 vs. 33.0; and 40.1 vs. 43.1 for November vs. February guinea grass's percent crude protein, percent crude fiber, and percent acid−detergent fiber, respectively.Use of a 6−week harvest interval and either guinea or elephant grass, but not star grass, was considered the best management combination for improved all−year quality herbage production in this tropical area.

AbstractTwo experiments were conducted to estimate the influence of initial cutting dates in March and April and of cutting frequencies on Guinea grass, elephant grass and star grass productivity. Increasing delay in date of first cut in the season resulted in a progressive increase in dry‐matter yield. 72–81% of the tiller population at any cut were vegetative and this helped to maintain good aftermath yield for each date of first cut. Early April cuts gave the highest dry‐matter yield and early March the least.Harvesting frequencies affected the sward productivity such that the annual dry matter yield increased with increasing harvesting interval from 6800 kg ha‐1 for a 3‐week interval to 13,000 kg ha‐1 for a 10‐week interval. The proportion of green leaf in the dry matter dropped from 57·7% at 3‐week intervals to 32·0% at 10‐week intervals. Seasonal effects showed that potential yield was reduced by a short interval between harvests early in the season but not late in the season. Species differences in quality and in the harvesting interval that gave the maximum yields were noted. These results are discussed in relation to management of the sward throughout the growing season.

SummaryFour varieties of Italian ryegrass (Lolium multiflorum), which have been found to differ in voluntary intake by livestock at the same level of digestibility, were examined in the year of sowing and in the two subsequent years in a field experiment. Eight dates of first harvest during May–June in the years after the year of sowing were compared. During May–June in these years the proportion of leaf in the crop was closely related to the stage of development of the crop relative to heading date, whereas yield and digestibility were more closely related to calendar date. As a result the later-heading varieties, S. 22 and Sabalan, had a higher proportion of leaf than the earlier-heading varieties, RvP and Tetila Tetrone, at a given yield and digestibility and this may at least partly account for higher intake in the former varieties. In addition, in Sabalan, the proportion of green leaf relative to dead was particularly high and the proportion of cell wall particularly low. The surface area per unit dry weight of leaf blade was much higher than that of ‘stem’, which may contribute to shorter retention time in the reticulo-rumen. Surface area per unit weight of both leaf blade and ‘stem’ declined with delay in date of first harvest.The yield of RvP relative to the other varieties was modest at the first harvest in the years after the year of sowing and high at subsequent harvests, in accord with National Institute of Agricultural Botany results. The high yield of RvP relative to the other varieties after the first harvest appeared to be associated with a relatively large number of tillers with their shoot apex below cutting height at the time of first harvest. It seemed that most of these tillers had emerged during the few weeks before that harvest. The proportion of tillers with their shoot apex below rather than above cutting height at the time of first harvest was higher in all four varieties than casual observation would suggest and the proportion remained rather high throughout May and June. The rapid rate of turnover of tillers in Italian ryegrass was confirmed.