African Journals Online
Ghana Journal of Agricultural Science

VOLUME 29 (1996) PART TWO
ABSTRACTS

SHEA (VITELLARIA PARADOXA) INTERCROPPING SYSTEMS IN NORTHERN GHANA: EFFECT OF CULTURAL PRACTICES AND CROP COMBINATIONS ON THE PERFORMANCE OF SHEA SEEDLINGS

K. OSEI-BONSU, M. R. APPIAH, F. M. AMOAH & F. K. OPPONG

Cocoa Research Institute, P. O. Box 8, Akim-Tafo, Ghana

The effects of cultural practices including twomethods of land preparation (conventional and zero-tillage), five intercrop sequences and two levels of NPK fertilizers on shea seedling growth (girth and height) were evaluated in a split-split plot experiment at Bole from 1984 to 1986. Conventional tillage significantly promoted seedling growth over zero-tillage (pre-planting herbicide application). Shea seedlings intercropped with rotations involving cowpea and maize such as cowpea-yam-maize and maize-cowpea-sorghum, were relatively bigger and taller than those intercropped with rotations that did not involve cowpea and maize. There was a positive residual effect of NPK fertilizers applied to the food crops on shea seedling growth especially on ploughed and harrowed land whereas there was no effect of zero tillage.

Original scientific paper. Received 7 Nov 95; revised 2 Jul 96.

(J.E.F.: Department of Animal Science, University of Ghana, P.O. Box 226, Legon, Ghana; A.J.A. & I.H.: Environmental Protection Agency, P.O. Box M.32, Ministries Post Office, Accra, Ghana)

The biomass productivity of the Winneba plains of Ghana was measured between January 1990 and February 1992. Ten sampling sites were chosen for the study. An area of 5.0 m W 5.0 m was demarcated and within it an area of 1.0 m W 1.0 m was harvested at monthly intervals, clipped by means of sickle at 5 cm above ground, and dried at 70 oC for more than 48 h for dry matter determination. Crop growth rate was then estimated. Dry matter yields were 5.29 and 6.31 tha-1yr-1 on the clayey and sandy soils respectively, averaging 5.87 t ha-1yr-1 for the Winneba plains. The respective crop growth rates on the clayey and sandy soils were 1.935 and 2.236 g m-3 day-1 between April and August, 0.867 and 1.0779 g m-2 day-1 between September and February and 0.296 and 0.742 g m-2 day-1 respectively in March. Carrying capacity may probably be in the range of 2.18 and 3.86 ha AU-1 per annum.

Original scientific paper. Received 5 May 95; Revised 8 Jul 96.

COMPARISON OF THE FERMENTATION QUALITY AND NUTRITIVE VALUE OF SILAGE MADE FROM LEUCAENA (LEUCAENA LEUCOCEPHALA (LAM.) DE WIT.) AND TWO TROPICAL GRASSES

J. E. FLEISCHER, Y. KAWAMOTO, M. SHIMOJO, I. GOTO & Y. MASUDA

(J.E. F., M.S., I.G. & Y. M.: Laboratory of Feed Science and Animal Behaviour, Faculty of Agriculture, Kyushu University, 46-06, Hakozaki, Fukuoka Shi, 812 Japan; J.E.F.'s: present address Department of Animal Science, University of Ghana, P.O. Box 226, Legon, Accra, Ghana; Y.K.: Department of Animal Science, College of Agriculture, University of the Ryukyus, Senbaru, Nishihara, Okinawa, 903-01, Japan)

About 10-month-old leucaena (Leucaena leucocephala (Lam.) De Wit.) grown in Japan and 52-day-old regrowth of guinea grass (Panicum maximum var. maximum cv. Gatton) and sorghum (Sorghum bicolor Moench cv. FS40IR), were chopped up to 3-5 cm lengths and ensiled in laboratory silos of 1.4-1.5 kg capacity. Samples were taken at 0, 1, 3, 5, 7 and 30 days of ensiling for laboratory determination of total nitrogen (T-N), volatile basic nitrogen expressed as per cent of T-N, pH, lactic acid, acetic acid, butyric acid, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL) and in vitro digestibility (IVD). There were significant differences (P<0.05) in the T-N and cell-wall components but not in IVD (P>0.05) among species. The final pH of the silages were 4.00, 3.94 and 5.27 for guinea grass, sorghum and leucaena respectively. Lactic acid was the dominant acid in all the silages. Significant differences (P<0.05) in lactic acid content were observed among the silages. No significant difference (P>0.05) was observed in acetic acid contents of the grass silages but these were significantly higher than that of the leucaena silage. Butyric acid was observed only in the grass silage. IVD of the silages after 30 days were 488.5, 519.6 and 515.5 g in kg DM of guinea grass, sorghum and leucaena respectively.

Original scientific paper. Received 29 Sep 95; Revised 8 Jul 96.

ENSILING CHARACTERISTIC AND NUTRITIVE VALUE OF NAPIER GRASS (PENNISETUM PURPUREUM SCHUMACH) COMBINED WITH OR WITHOUT LEUCAENA (LEUCAENA LEUCOCEPHALA (LAM.) DE WIT.) AS INFLUENCED BY STARCH OR FORMIC ACID ADDITION

(J.E. F., M.S., I.G. & Y. M.: Laboratory of Feed Science and Animal Behaviour, Faculty of Agriculture, Kyushu University, 46-06, Hakozaki, Fukuoka Shi, 812 Japan; J.E.F's present address: Department of Animal Science, University of Ghana, P.O. Box 226, Legon, Accra Ghana; Y.K.: Department of Animal Science, College of Agriculture, University of the Ryukyus, Senbaru, Nishihara, Okinawa 903-01, Japan.)

About 12-week-old napier grass Pennisetum purpureum Schumach) and 10-month-old Leucaena (Leucaena leucocephala (Lam.) de Wit.) both from a naturalized

field and chopped to about 3.5 cm were used. The grass and legume were combined in a grass:legume ratio of 7:3. There were five treatments viz., napier grass

(T1), leucaena (T2), napier grass-leucaena (T3), napier grass-leucaena with starch added (50 g starch/kg fresh mixed forage) (T4) and napier grass-leucaena with formic acid added (2.3 ml per kg fresh mixed forage) (T5). Each of the treatment sample was stuffed into a two-litre laboratory silo (1.4-1.5 kg sample) and stored for 42 days. Samples were taken at the time of silo filling and after ensiling and analyzed for total nitrogen (T-N), volatile basic nitrogen (VBN) as per cent of total N, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL) and in vitro dry matter digestibility (IVDMD). Napier grass (T1) had significantly lower (P<0.01) T-N but higher cell wall components exc ept for ADL compared to T2. The IVDMD of T1 was significantly higher (P<0.05) than that of T2. Combination of napier grass with leucaena

increased the T-N but reduced the fibres. Treatments T4 and T5 significantly differed (P<0.05) in T-N, cell wall components and IVDMD from each other. TreatmentT2 had a significantly higher (P<0.05) pH than the others. Lactic acid was signficantly developed in T4. Only T3 had some butyric acid. Treatment T4 had the lowest VBN. NDF in all silages slightly decreased while ADF, cellulose and ADL in some cases slightly increased. IVDMD slightly decreased or remained unchanged on ensiling.

Original scientific paper. Received 9 Feb 95; revised 8 Jul 96.

STUDIES ON THE VARIATIONS IN THE CHEMICAL COMPOSITION OF LEUCAENA (LEUCAENA LEUCOCEPHALA (LAM.) DE WIT.) DURING ENSILING

(J.E. F., M.S., I.G. & Y. M.: Laboratory of Feed Science and Animal Behaviour, Faculty of Agriculture, Kyushu University, 46-06, Hakozaki, Fukuoka Shi, 812 Japan; Y.K.: Department of Animal Science, College of Agriculture, University of the Ryukyus, Senbaru, Nishihara, Okinawa, 903-01 Japan; J.E.F.'s present address: Department of Animal Science, University of Ghana, P.O. Box 226, Legon, Accra Ghana)

The fermentation quality and nutritive value of leucaena ensiled either as whole forage or separate stem and leaf fractions were investigated. About 10-month-old leucaena (Leucaena leucocephala (Lam.) De Wit.) grown in Okinawa Island, Japan, was used.Samples were chopped to about 4 cm lengths and stuffed into laboratory silos of 1.4-1.5 kg capacity. Samples were taken at 0, 1, 3, 5, 7 and 42 days of ensiling for the laboratory determination of total nitrogen (T-N), volatile basic nitrogen fibre (VBN) expressed as g kg-1 of T-N, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL), in vitro digestibility (IVD), lactic acid, acetic and butyric acid. The leaves had the highest T-N (52 g kg Dm-1)] IVDM (695.6 g kg-1) and lowest cell wall components, while the stem had the lowest T-N (15.8 g kg Dm-1) and IVDM (334.9 k kg Dm-1) but highest cell wall components. However, the whole forage had intermediate values. These differences were significant (P<0.01). The pH of the silages declined with advancing ensiling time but was generally high ( P 35.00) in all three. Although lactic acid was the dominant acid in all fractions, the difference between leaf and stem was significant (P<0.01) but that between either the leaf or stem and, whole forage were not significant (P>0.05). Acetic acid was very low in all and showed no significant difference (P> 0.05) among silages. Ensiling only slightly decreased the IVD and T-N in whole forage and leaves but not in stem.

Original scientific paper. Received 29 Sep 95; Revised 8 Jul 96.

CONSTANT TEMPERATURES AND THE RATE OF SEED GERMINATION IN MAIZE (ZEA MAYS L.) OF CONTRASTING ENDOSPERM

Crops Research Institute, Council for Scientific and Industrial Research, P. O. Box 3785, Kumasi, Ghana

The germination of quality protein maize (QPM) cultivar, Obatanpa, was compared to normal endosperm (NEM) cultivar, Okomasa, on a temperature gradient plate at constant temperatures ranging from 15-45 oC. Germination occurred at all temperatures except at 42.5 oC for the QPM cultivar and 45 oC for the NEM cultivar. The rate of germination of the NEM cultivar was faster than that of the QPM cultivar at all temperatures. The thermal times for median germination were 46 for QPM and 40.7 oCd for the NEM cultivar. The cardinal temperatures (base, Tb, optimum, To and ceiling, Tc) for the NEM cultivar were Tb: 7, To: 30 and Tc: 48.2 oC. The corresponding values for the QPM cultivar were Tb: 7.6, To: 27.5 and Tc: 43.4 oC. The base and optimal temperatures were not significantly different but the ceiling temperature for the QPM was significantly lower(P<0.05). For each cultivar, a positive linear relationship was established between temperature and rate of germination from the base temperature, Tb, at which germination rate was zero to the optimum temperature, To, at which germination rate was maximal. Above To, negative linear relationships were established between temperature and rate of

germination to the respective ceiling temperatures, Tc, at which germination rate was again zero.

Original scientific paper. Received 22 Jan 96; revised 10 Jul 96.

THE EFFECT OF SUPPLEMENTARY FEEDING ON THE WORK OUTPUT AND PHYSIOLOGICAL RESPONSE OF INDIGENOUS CATTLE IN ON OIL PALM PLANTATION

Box 80, Accra, Ghana; W.S.A.: CSIR Secretariat, P. O. Box M.32, Accra, Ghana)

The effect of supplementary feeding on the work output, respiratory rate and diurnal rectal

temperature of Sanga and West African Shorthorn (WASH) cattle working on an oil palm plantation was studied. Supplementary feed intake of the Sanga was 2.8 kg while that of the WASH was 2.4 kg. The average bodyweights of the Sangas and the WASH were 328 kg and 256 kg at the beginning and 348 kg and 262 kg at the end of the trials respectively. Supplementation had no significant effect on work output under the prevailing liberal grazing conditions of the trial. The respiratory rates of the Sangas and the WASH at work when given supplements were 38 and 51 breaths/min respectively and 35 and 41 breaths/min when they were at work without supplementation. The rectal temperature was significantly higher (P<0.05) after work in both breeds with and without supplementation. However, no significant difference (P>0.05) in the rectal temperature was noticed between the two breeds after work. The average weight of bunches of oil palm fruits carried by a bullock cart per day was 2.03 tonnes while that of a wheel barrow used by human porters was 1.61 tonnes. It was more economical to use bullock carts than wheel barrows.

Original scientific paper. Received 31 Jul 95;revised 8 Aug 96.

ESTIMATES OF VARIABILITY AND GENETIC GAINS IN COWPEA (VIGNA UNGUICULATA (L.) WALP)

M. I. UGURU

Department of Crop Science, University of Nigeria, Nsukka, Nigeria

The grain and vegetable cowpea types were hybridised with a view to estimating the genetic variability, heritability and expected genetic gains in their progenies. Whereas there was a wide range of variation in pod length, the variations in days to 50

per cent flowering, pods/plant, seeds/pod, 100-seed weight and grain yield were of low magnitude. There were indications of considerable dissimilarities in the loci of both cowpea types. Heritability values and genetic gains in days to 50 per cent flowering,

pod length, seeds/pod, 100-seed weight and grain yield were higher in progenies from the hybridized vegetable and grain cowpeas than in the offspring from the cross between two grain cowpeas. The magnitude of the values of the estimates of heritability and genetic gain suggested that individual plant selection would be effective in crosses involving either two vegetable cowpeas or a vegetable and a grain cowpea.

Original scientific paper. Received 6 Sep 95; revised 29 Aug 96.

QUALITY EVALUATION OF SOME RICE CULTIVARS GROWN IN GHANA

J. T. MANFUL, J. K. AKATSE & A. OSEI-YAW J.T.M. & A. O-Y.:

Food Research Institute, CSIR, P. O.Box M.20, Accra, Ghana; J.K.A.: Irrigation Development Centre, P.O. Box 273, Ashaiman, Ghana

Ten cultivars of locally grown rice were screened for yield and other desirable agronomic characteristics. Their milling characteristics were evaluated by dehusking in a Satake (THU-34A) Testing Rice Husker and polishing in a BSO8A Single Pass Rice Pearler.

The physical quality and proximate composition of the cultivars were determined. Cooking characteristics and sensory evaluation were carried out on the samples. Varieties B-189 and IR-72 had the highest average yields. Variety IR-66 had the shortest growth

duration with IR-72 recording the lowest plant height. Akpafu variety had good milling characteristics, that is, low level brokens with ITA-304 being most susceptible to breakage. Variaty TOX-3108 had the highest overall cooking and sensory acceptability

rating with Akpafu being the least acceptable. The suitability of each variety for various local dishes was also evaluated. Whilst B-189 was good for all local dishes, Akpafu was found to be best

Original scientific paper. Received 7 Nov 95; revised 10 Sept 96.

RESPONSE OF BROILER CHICKS TO DIETS CONTAINING VARYING LEVELS OF CASHEW NUT OIL AND PALM OIL

(A.A.O.: Department of Animal Production and Health, Ladoke Akintola University of Technology, Ogbomoso, Nigeria; S.O.O.: Department of Agricultural Education, St Andrew College of Education, Oye, Nigeria)

ABSTRACT

Chemical characterization of palm oil (PO) and cashew nut oil (CNO) involving saponification value, iodine number and degree of acidity were carried out. Both oils were included in diets of starting broilers (0 - 4 weeks) at three levels (10, 25 and 50 g/kg) as energy supplements in replacement of the maize in a basal control diet. At the finisher phase (5 — 8 weeks), the birds were fed a common broiler finisher diet to investigate the carry-over effects of starter dietary treatments on finishing broiler performance. Results indicated that birds fed PO gave comparable performance with those on control diet while increasing levels of CNO resulted in a consistent decrease (P <0.05) in feed intake and weight gain. Mortality and feed efficiency were adversely affected at levels more than 10 g/kg CNO. At the finisher phase, birds on 10 and 25 g/kg CNO had a rapid performance recovery rate which was not markedly evident with the 50 g/kg CNO. It appears that CNO should be neutralized before incorporation in broiler starter diets at levels more than 10 g/kg.

Original scientific paper. Received 24 Jul 95; revised 25 Sep 96.

EFFECTS OF FREQUENCY OF SPRAYING NEEM SEED EXTRACT ON THE LEPIDOPTERAN PESTS OF THE EGG PLANT (SOLANUM INTEGRIFOLIUM)

University of Ghana Agricultural Research Station, Kade, Ghana

Six treatments of different intervals of spray (1, 2, 3, 4, 5 and 6 weeks) of neem seed extract at 20 kg neem seed/ha and a control of no neem spray, were evaluated against lepidopteran pests of the egg plant. Leaf, shoot and fruit damage on plants sprayed ateither 1- or 2- week intervals was less (< 30 %) than on those with intervals of spray beyond 2 weeks (35-58 %). Nevertheless, the performance of the neem extract-treated plants sprayed at all the six frequencies was better than the untreated plants which produced the lowest yield per hectare (2.0 kg). This indicates the importance and pest status of the lepidopteran insects on the egg plant. The results from this experiment confirm the potential of neem extract as an alternative bio-pesticide for control of insect pests.

Original scientific paper. Received 26 Jan 95; revised 26 Sep 96.

FUNGITOXICITY SPECTRA OF CRUDE EXTRACTS OF THREE GHANAIAN MEDICINAL PLANTS

Department of Crop Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Steam distillates from three Ghanaian medicinal plants, Ocimum gratissimum (L.), Xylopia aethiopica (Dunal) Rich and Cymbopogon citratus (D.C.) Stapf, were tested for fungitoxicity against 20 fungal species. A fungitoxicity spectrum (FS) was calculated for each extract based on per cent inhibition of fungal growth. High FS values of 4.8 and 3.5 (maximum assignable value = 5) were, respectively, associated with extracts of O. gratissimum and C. citratus. A low value of 1.4 was recorded for X. aethiopica. Whereas extract of O. gratissimum exhibited complete fungicidal activity towards 14 of the 20 fungi, that of C. citratus was fungicidal to only three. The extract of X. aethiopica was fungistatic but not fungicidal.

Original scientific paper. Received 14 May 96; revised 27 Sep 96.

SATURATED HYDRAULIC CONDUCTIVITY VALUES OF SOME FOREST SOILS OF GHANA DETERMINED BY A SIMPLE METHOD

Department of Soil Science, School of Agriculture, University of Cape Coast, Cape Coast, Ghana

A simple falling-head method is presented for the laboratory determination of saturated hydraulic conductivity of some forest soils of Ghana. Using the procedure, it was found that saturated hydraulic conductivity was positively and negatively correlated with sand content and clay content, respectively, both at P = 0.05 level. Further, the statistical

functional relationships between saturated hydraulic conductivity and sand content and clay content were best described by an exponential function, respectively.

Original scientific paper. Received 8 Nov 94; revised 1 Oct 96.

THE PROBLEM OF WEEDS UNDER CONTINUOUS CROPPING SYSTEMS IN THE SCRUB AND THICKET VEGETATION BELT OF THE CENTRAL REGION, GHANA

Department of Crop Science, School of Agriculture, University of Cape Coast, Cape Coast, Ghana

The long term effects of three cropping systems, monocropping, two-course rotation (maize/cowpea or sweet potato) and three-course rotation (maize/sweet potato/cassava), on the quantity and quality of both the above-ground weed flora, and the non-dormant portion of the soil's weed seed bank were studied at the Teaching and Research Farm of the School of Agriculture in Cape Coast. After 14 years of continuous cropping, it was realized that there were no significant differences in species composition of the weed flora among the three cropping systems whilst the rotations were significantly less weedy than monocropping. The intensity of rotation had some influence on the population of monocots which were more abundant in monocropping than in the two-course and three-course rotations, in the order of decreasing population. Fears of a shift from the easy-to-control annuals to the hard-to-control perennials were unfounded. The only problematic perennial found in appreciable numbers was Cyperus rotundus. Only seven out of the total of 32 species recorded in the weed flora were found in the non-dormant portion of the

seed bank. The two-course rotation with relatively higher tillage frequency had the lowest number of non-dormant seeds followed by monocropping and three-course rotation, in order of increasing populations. An average of 82,539 non-dormant seeds were recorded in an area of 1 m2 in the top 20 cm of moist soil in the study. The bulk of the seeds was contributed by mostly the short cycle and tufted annual monocots including Brachiaria lata, Dactyloctenium aegyptium and Eleusine indica. It was estimated that only one out of a total of 48,821 non-dormant seeds of Dactyloctenium aegyptium could develop and reach maturity. Corresponding figures for Eleusine indica and Brachiaria lata were one out of 32,240 and 2,896 non-dormant seeds, respectively. Cyperus rotundus was the only species in which the quantity of tubers in the seed bank was related to and could be used to predict the level of shoot infestation, regardless of cropping system.

Original scientific paper. Received 29 sep 95; revised 30 Oct 96.

APPLICATION OF SOIL SOLARIZATION TO CONTROL ROOT-KNOT NEMATODES AND WEEDS IN TRANSPLANTED TOMATO

School of Agriculture, University of Cape Coast, Cape Coast, Ghana

The effects of 0, 10, 20 and 30 days of tightly covering of tomato beds with thick (50 mm) transparent polyethylene plastic sheet prior to transplanting were assessed on soil temperatures, root-knot nematodes, specific weeds, and growth and fruit yield of tomato in a field experiment at the Teaching and Research Farm of the University of Cape Coast in 1992. Mean soil temperatures ranged from 44 to 53 oC at 5 cm depth and from36 to 46 oC at 10 cm depth with temperatures increasing with successive increases in period of solarization. Soil nematodes, mostly root-knot (Meloidogyne spp.) were significantly reduced and the longer the period of solarization the greater was the reduction. Root-galling incidence in tomato was likewise reduced significantly by

solarization. Annual weed species which reproduce by means of numerous tiny seeds, including Boerhavia diffusa, Ageratum conyzoides, Euphorbia heterophylla and Tridax procumbense, were effectively controlled particularly by long periods of solarization. On the other hand, Cynodon dactylon which reproduces vegetatively by stolons was partially controlled. The predominant weed species Cyperus rotundus, a perennial, could not be controlled even by the longest period of solarization. Soil solarization also improved crop height and fruit yield. This is attributed possibly to its lethal effect on nematodes, weeds and its favourable influence on mineralization of soil organic matter, and reduction in fruit decay incidence.

Original scientific paper. Received 2 Apr 96; revised 30 Oct 96.

FERMENTATION CHARACTERISTICS AND CHANGES IN NUTRITIVE VALUE OF GUINEA GRASS-LEUCAENA ENSILED WITH OR WITHOUT ADDITIVE

(J.E.F., M.S., Y.M. & I.G.: Laboratory of Feed Science and Animal Behaviour, Faculty of Agriculture, Kyushu University, 46-06, Hakozaki, Fukuoka Shi 812 Japan; Y.K.: Department of Animal Science, College of Agriculture, University of Ryukyus, Senbara,

Nishihara, Okinawa, 903-01 Japan; J.E.F.'s present address: Department of Animal Science, Faculty of Agriculture, University of Ghana, Legon, Ghana)

Fifty-two-day-old guinea grass (Panicum maximum var. maximum cv. Gatton) which received 150 kg N per hectare and 10-month-old leucaena (Leucaena leucocephala (Lam.) De Wit.) were used. There were five treatments viz., guinea grass (T1), leucaena (T2), guinea grass-leucaena (T3), guinea grass-leucaena with starch (T4) and guinea grass-leucaena with formic acid (T5). Both guinea grass and leucaena were mixed in a grass:legume ratio of 7:3 in T3, T4 and T5. Samples were stuffed into laboratory silo (1.4-1.5 kg sample) and stored for 42 days. Samples were taken at and after ensiling and analysed for total nitrogen, volatile basic nitrogen as per cent of total N, pH, lactic acid, acetic acid, butyric acid, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL) and in vitro dry matter digestibility (IVDMD). Guinea grass had significantly lower (P<0.01) nitrogen content but higher content of fibre compared to leucaena. The IVDMD values (50%) were similar (P<0.05) in both guinea grass and leucaena. Combining guinea grass with leucaena significantly (P<0.05) raised the nitrogen content of the mixture but slightly reduced the cell wall components. It also raised the IVDMD value (54 per cent) though not significantly. Addition of starch reduced the nitrogen content and the cell wall consistency but increased the IVDMD value (56 per cent). These changes were significant (P<0.05). Guinea grass silage had a significantly (P<0.05) lower pH and volatile basic acid (VAN) than leucaena. Guinea grass with leucaena starch had the lowest pH but was not significantly different from T1, T3 and T5. The lactic acid content of T4 was significantly higher (P<0.05) than the others. T5 has the lowest VBN.

Original scientific paper. Received 9 Feb 96; revised 5 Nov 96.

BIOMASS PRODUCTIVITY AND CARRYING CAPACITY OF THE NATURAL GRASSLAND ON THE ACCRA PLAINS OF GHANA

(J.E.F.: Department of Animal Science, Faculty of Agriculture, University of Ghana, P. O. Box 226, Legon, Accra, Ghana; J.A.A.. and H. I.: Environmental Protection Council, P. O. Box M.326, Accra, Ghana)

The study assessed the biomass productivity and then estimated the carrying capacity of the natural grassland on the Accra Plains of Ghana between January 1990 and February 1992. Eleven sampling sites with varying grass association, soil type and ease of accessibility were sampled. In each sampling site an area of 5.0 m W 5.0 m was demarcated within which 1.0 m W 1.0 m quadrat was sampled. Sampling was done by clipping the herbage at 5 cm above ground. This was later dried at 70 oC for more than 48 h for dry matter determination. Crop growth rate was then estimated. Overall dry matter yield was 4.80 t ha-1 yr-1. It was 4.667 and 5.03 t ha-1 yr-1 on the clayey and sandy soils respectively. Three periods of crop growth rate were observed. These were i) period of very high productivity (April-July) with values of 2.128 and 2.286 of g m-2 day-1 for clayey and sandy soils respectively; ii) period of moderately high productivity (October-February) where the growth rate averaged 1.179 and 1.213 g m-2 day-1 for clayey and

sandy soils and iii) periods of at least crop growth rate (March and September) with value of 0.635 and 0.749 g m-2 day-1 for clayey and sandy soils. The overall average carrying capacity was 3.60 ha AU-1 yr-1.

Original scientific paper. Received 9 Feb 95; revised 5 Nov 96.

REPRODUCTIVE AND MILKING PERFORMANCE OF A HERD OF FRIESIAN W N'DAMA CATTLE

(P.K.K. & K.A.: Dairy Beef Cattle Research Station, University of Science and Technology, Kumasi, Ghana; S.A.O. & P.G.: Department of Animal Science, University of Science and Technology, Kumasi, Ghana)

Production records of a herd of Friesian W N'Dama cattle reared on-station were examined to assess their potential for use as dairy animals in the tropics. In addition, the radio- immunoassay technique was used to measure plasma progesterone concentrations to determine the attainment of puberty and resumption of ovarian activity postpartum in heifers and cows, respectively. A Friesian bull was always used to serve females on heat. Bull calves were significantly (P< 0.05) heavier at birth than heifer calves; the respective mean (1SE) weights being 3011 kg and 2711kg. The season of birth also significantly affected birth weight with calves born in the wet season being heavier than their dry season born counterparts (wet = 3111 kg; dry = 2611 kg; P<0.05). Puberty was attained at a mean age of 704144 days when the heifers weighed on the average 18117 kg. Heifers calved for the first time at 990 144 days of age and at a mean weight of 2501 6 kg. Ovarian inactivity postpartum lasted a mean period of 83115 days and the mean calving interval was 371120 days. There was a significant (P<0.01) genotype effect on lactation milk yield and length of lactation. First generation (F1) cows had relatively poor milking performance, producing a mean of 7941260 kg of milk in 159133 days of lactation as compared to second generation (F2) cows which produced 17671137 kg of milk in 298118 days. Cows which calved in the wet season lactated significantly (P<0.05) longer than those which calved in the dry season (260126 days and 193120 days, respectively). The effect of the interaction between season and partity on lactation milk yield was also significant (P<0.05) with first parity cows which calved in the dry season producing less milk than the others.

Original scientific paper. Received 1 Apr 96; revised 8 Nov 96.

THE UTILIZATION OF AZOLLA AS A SOURCE OF NITROGEN FOR RICE PRODUCTION IN GHANA

University of Ghana Agricultural Research Station, Kpong, Ghana

The performance of the local strain of Azolla, Azolla pinnata var. africana, as a green manure for rice was compared with inorganic nitrogen alone and a combination of Azolla and inorganic nitrogen. The Azolla was incorporated under the rice crop (cv. GRUG 7) grown under irrigation on the vertisol. Within a period of 4 weeks and a doubling time of 5 days, a total biomass of 18 t/ha of Azolla, equivalent to 25 kg N/ha was produced. This is 28 per cent of the optimum recommended nitrogen rate (90 kg N/ha) for rice cultivation on the vertisols of the Accra Plains. Azolla, in combination with 40 kg N/ha ammonium sulphate fertilizer, gave significantly higher grain yields than Azolla only, 60 kg N/ha ammonium sulphate fertilizer and the control plot. No significant grain yield differences were observed between the single and double Azolla incorporations, but the double incorporation of Azolla only gave a yield equivalent to that obtained under 60 kg N/ha ammonium sulphate while a lower yield was observed for the single incorporation. The grain yields were 4.8, 3.5, 2.7 and 1.8 t/ha for the Azolla plus N-fertilizer, 60 kg N/ha, Azolla only and the control plot respeectively.

Research and development note. Received 10 Oct 89; revised 12 Dec 96.