Viability status of Cenchrus ciliaris seeds in the three farms of the sub-humid eastern agro-ecological zone of Tanzania

J B Kizima, E J Mtengeti* and S Nchimbi-Msolla*

Ministry of Livestock and Fisheries Development, Livestock Research Institute, P.O. Box 5016 Tanga, Tanzania
jkizima@yahoo.com
* Faculty of Agriculture, Sokoine University of Agriculture, P.O. Box 3004, Morogoro, Tanzania

Abstract

Low level of some soil nutrients from soils and older age of swards, seem to be factors among other factors that contribute to low pasture seed viability in Tanzanian sub-humid farms. A laboratory study was conducted to assess viability status of Cenchrus ciliaris seeds and soil fertility status from three farms namely Mazimbu in Morogoro, vikuge in kibaha and Tanga, Cenchrus ciliaris pasture species is among the most demanded grass species by livestock keepers in Tanzania due to its tolerance to drought conditions.

Spikelet germination rate was 8.33% for Mazimbu, 0.25% for Vikuge and 1.83% for Tanga farms. Total soil Nitrogen was observed to be at very low levels i.e 0.08%, 0.13% and 0.12% for Vikuge, Tanga and Mazimbu farms respectively.  From this study it could be concluded that old age of sward produced low quality seeds in terms of viability, and this could be further exacerbated by low soil fertility. Further studies on fertilizer rates, irrigation during dry season, rows spacing and seed health challenges are required to bring more understanding on grass seed production in the similar agro-ecological zone.

Keywords: age of the sward, grass seeds quality, soil fertility

Introduction

Livestock sector is important for the economy of Tanzania as is for many other developing countries. In Tanzania, the sector contributes about 5.9 % of the Gross Domestic Product (GDP) and employs about 40% of the 3.9 million agricultural households who are involved in crops and livestock production (MLD 2006).  The growing human and livestock populations increase demand on land resources, and is causing a decline of grasslands for other uses and create forage shortage for both traditional and improved ruminants keeping systems.  

According to Pamo et al 2000, sub humid zones have a range of 1000 to 1500 millimetres of annual rainfall and the growing period of 180 to 270 days. Climatic conditions in these eastern sub humid regions of Tanga, Coast (Pwani), Morogoro and Dar es Salaam in Tanzania are favourable for agriculture and livestock production. Favourable climate condition and availability of markets for the livestock products have motivated people in this agricultural zone to solicit land for intensive ruminant livestock farming to produce milk and meat. However forages shortage during the dry season is still a constraint for high productivity all the year round. Sustainable solution to forage shortage is possible when technical efforts are invested to improve production and utilization of natural and planted forages. It is well understood that improved ruminant production system requires high quality forages, especially for dairy and beef cattle (Kumwenda et al 2003).

Pasture establishment aims to improve productivity of livestock production system through increased forage yield. However pasture establishment requires good quality seeds. According to ASARECA (2007), quality seeds are the basic foundations of any improved ruminant production system and economic gains among farming communities. In order to develop a good functional seed production system responding to market oriented demands more expertise is required to support policy institutions. Therefore, development of technologies to improve grass pasture seed yield and quality in seed production industry will be a step forward towards quality forage production in Tanzania in order to improve ruminant livestock productivity. This study therefore, aimed to assess viability status of Cenchrus ciliaris seeds from three prominent pasture seed producing farms (Mazimbu, Vikuge and Tanga) as an initiative to create awareness to stakeholders for pasture grass seed quality improvement to meet the growing demand.

Materials and methods

Study areas

This study was conducted in three prominent pasture seed farms in eastern sub humid agro ecological zone. The farms studied were:-

Vikuge Pasture seed farm at Kibaha – Coast region, with a bimodal rainfall pattern (1000- 1500 mm annual rainfall) Fig 1. The mean temperature ranges from 21 ^oC to 31 ^oC.

Figure 1: Rainfall distribution of Kibaha, Tanzania

Tanga farm at Livestock Research Institute  which is located in Tanga region with a bimodal rainfall pattern (1230 - 1400 mm annual rainfall) Fig 2. The mean temperature ranges from 26^oC to 33^oC.

Figure 2: Rainfall distribution of Tanga, Tanzania

Mazimbu farm at  Sokoine University of Agriculture which is located in Morogoro region with a bimodal rainfall pattern (1000- 1200 mm annual rainfall) Fig 3. With the mean temperature of 18 – 30 ⁰C

Figure 3: Rainfall distribution of Morogoro, Tanzania

Preliminary survey and farm visits:

Three farms were visited in November 2010 to interview farm managers using a structured checklist on daily production activities, practices and challenges facing pasture seed production in their farms. During the farm visit the samples of Cenchrus ciliaris seeds and soils were collected for laboratory analyses.

Soil sampling

Soil samples were collected randomly in the seed farm and mixed to constitute a representative sample from each farm. The soil samples were taken at a depth of 0 – 20 cm from the soil surface. The collected soil samples were air dried and ground to pass through 2 mm sieve before laboratory analysis. Total Nitrogen N and soil extractable Phosphorus P were analyzed using Micro- kjeldahl and Bray I methods, respectively (Bremner and Mulvaney 1982; Olsen and Sommer 1982).

Seed sampling

In each farm a seed lot of 3 kg of Cenchrus ciliaris was sampled from the seed stock available for sale and delivered to the laboratory for seed quality analysis.  

Seed moisture content test

The levels of moisture content of the seeds sampled were determined at SUA using oven method (direct method). Two empty petri dishes were weighed before dropping 10 g of Cenchrus ciliaris  seeds and then dried in the oven at  103°C for  17 hours and allowed to cool in a desiccator for 15 minutes. The dried samples were then reweighed and thereafter, moisture content calculated.

Testing of seeds viability

Caryopsis percentage assessment of the seeds from each farm was conducted. From each sample, four hundred spikelets were dissected to assess presence of caryopsis (grain) using forceps under a hand lenses (at magnification of X 20). The same exercise was repeated three times for each sample to find an average percentage of caryopsis per spikelet. Before starting an assessment of germination potential, potassium nitrate solution was used to saturate the germination substrate so as to break seed dormancy. All seeds and blotter papers were soaked in a solution of 0.2 % KNO₃ prepared by dissolving 2 grammes of KNO₃ in 1 litre of water. Germination test was then conducted (for spikelet and naked caryopsis) using petri dishes set in the germination cabinet at room temperature ranging from 25 to 30⁰C. Hundred seeds were placed on moist blotter paper in each petri dish; during the following days of an experiment, seeds were moistened using distilled water to avoid contamination. Three replications of petri dishes were set and germinated spikelets and naked caryopsis were then counted and recorded daily from the day 3 to 28 days of germination, according to the recommendation of ISTA (2009). Obtained results from laboratory test on germination of Cenchrus ciliaris seeds from three farms were then subjected to SAS statistical package programme to compare the means difference.

Results and discussion

Demand of C. ciliaris seeds from the respective farms  

Cenchrus ciliaris grass pasture species was the dominant specie covering larger part of established grass species in the surveyed farms. The main cultivar was C. ciliaris Cultivar Biloela, however some traces of C. cilaris cultivar gayndah were observed in Vikuge and Tanga grass seed production farms. Other improved grass species were Chloris guyana, pennisetum purperium and Trypsacum laxum.  Looking of the data of purchased seeds at vikuge (Table 1), demand of the seeds was observed to be high covering many regions of the Tanzania. Both seeds and vegetatives splits are sold to customers, and use of vegetative splits for establishment was observed to cost much compared to seeds in terms of acreages.

Cenchrus ciliaris grass seed cv. Biloela demand is high probably due to its drought tolerance characteristics and adaptability to sub-humid agro ecological zone and other regions of Tanzania. This finding is similar to the results that were reported by Kumar et al (2005) on Cenchrus ciliaris from India. In this study the species exhibited high productivity, perennially and persistent to drought conditions probably due to its tuft-rhizomatous growth habit.   Vikuge pasture seed farm is the most prominent pasture seeds farm for many years as compared to others which have just started seed and hay production recently. Pasture seeds that are produced in the farms (Tanga and Mazimbu) are used for own farms expansion initiatives.

Agronomical practices in Vikuge, Mazimbu and Tanga pasture seed farms

Normally the pasture seed farms is left intact  during the long rain season of March to June, and the seeds are harvested in  July and August during the dry season of the three respective farms (Figure 1,2 and 3). However, during short rains sometimes seeds set and were also harvested when mature. Produced seeds were harvested and air dried in open room and stored cumulatively mixed with the remaining stock. No irrigation was reported for seed production in all three farms. Grass seed production was reported to be very sensitive during the wet season due to high levels of humidity which is a predisposing factor to diseases attack. The mature spongy cylindrical inflorescence of Cenchrus ciliaris tends to absorb moisture during the rainy season, and this creates favourable site for fungal infection and multiplication. According to FAO (1986), pasture seeds production using irrigation system was noted to produce good quality seeds with few challenges of diseases, and less rainy weather damages during the seed harvest.  In all the three farms, the sward used for hay production was also used for seed production (Table 2).  Vikuge pasture seed farm had older C. cilaris sward (8 years) for seed production as compared to other two farms (one year for Mazimbu and five years for Tanga farm). Swards for seed production were basically observed to be saving two purposes, hay and seed production.  During hay harvest, it was observed that the left cut tillers of swards were ranging from 15 – 25 cm of height on average, where drum and disc type of mowers were commonly used to harvest hay in all farms.  During an interview with farm managers, Tanga and vikuge farms were reported not to apply industrial fertilizer or manure for seed production for some years. However, Mazimbu farm was observed to apply manure and Urea( but the rate was not known).

Challenges facing grass seed production in sub-humid farms

Results in Table 3, indicate the main challenges that face pasture seed production activities. Lack of funds was observed to be a big challenge to all three farms. These farms depended on funds from government disbursement of which their adequacy and timing were not guaranteed. However, the marketing of seeds was observed not to be a challenge/constraint for Vikuge farm. This was reported to be due to many years of experience in pasture seed production and more contact to customers; however they still need more funds for further promotion and production strategies.  Tanga farm was reported not to face seed marketing challenge because  the seeds produced from this farm were used for farm expansion in their annex Buhuri farm, about 10 km from the main farm.  Mazimbu farm showed a doubt on marketing probably because they have recently started seed production and few customers were aware of their products.

Levels of pasture seed moisture content

Moisture content of seeds in Mazimbu farm was observed to be 5.6%, while those of Vikuge and Tanga farms were 5.2% and 5.0%, respectively. These findings are within the recommended moisture content (below 8%) for safe storage of grass seeds (International Seed Testing Authority  2010). The lower the moisture content the safer the storage of the seeds.

Colour of seed lots

It was observed that colour of the seeds (photo 1) from the three farms were a bit different although they were all harvested in July 2010. The colour of seeds from Mazimbu farm was kharkish while those from Vikuge and Tanga were a bit brownish. This may need more studies on fungal infection since this could have affected the colour of seeds.

Photo 1: Seed colour (kharkish and brownish) Farm 3-Mazimbu, farm 2-Tanga and farm 1 -Vikuge

Test for seed viability

The purity of seeds from Vikuge and Tanga farms was observed to be 90% (Table 4). However the purity for pasture seeds from Mazimbu farm was slightly below (86.7%) the recommended purity of 90% (FAO 1993). The germination test for spikelet and caryopsis showed significance (P < 0.05) difference between the farms. The spikelet germination percentages were 8.33, 1.83 and 0.25 for Mazimbu, Tanga and vikuge farms, respectively. The study conducted in a neighbour country of Kenya by Mganga et al (2010) reported a bit higher germination of 12% for Cenchrus ciliaris seeds.  The results from study and those reported from Kenya were below minimum germination (spikelets) of 20% for seed quality standards as for FAO quality declared seed set for Cenchrus ciliaris species (FAO  1993). The differences of results between the farms and country may be due to low level of soil fertility (Table 5), and other factors. This is supported by Bekunda et al (2004) that average crop yields in East Africa are alarmingly below potential yields (values obtained at national research stations). This may be due to complex interactions between several factors including soil fertility pests, diseases, climate and management.  Low fertility levels (Table 4) in farms may have affected caryopsis (grain fill) resulting in more empty spikelets harvested which lower germination percentages.  Germination of caryopsis started earlier from the third day of experiment while the germination for spikelets started later in the sixth day, this was due to the fact that caryopsis were naked and easily soaked than spikelets. Basing on Caryopsis germination, seeds from Tanga showed higher results (56.17 %) followed by Mazimbu and Vikuge. 

Analysis of soil fertility

The soil fertility status of the soil samples collected from the farms showed some deficiencies in some nutrients (Table 5). Looking at levels of soil macronutrients N,P,K that are required by plants in larger amounts,  Nitrogen was observed to be deficient in all studied farms.  Total Nitrogen for Vikuge farm was at very low level of 0.08%, while the soils from Tanga and Mazimbu showed low levels  of 0.12 and 0.13 respectively  percentages (Moberg  2000). It was therefore observed that soil fertility levels in terms of total nitrogen in all three studied farms were deficient, and this might be a cause of poor seed setting which affected seed quality in terms of viability. According to Eckert (2012), a nitrogen-deficient plant is generally small and develops slowly because it lacks the nitrogen necessary to manufacture chlorophyhyll for efficient photosynthesis.

The results for Phosphorus nutrient from the soils that were analysed showed that, P level was very high for the Mazimbu farm soils (46.19 mg/kg), whereas they were very low at Vikuge and Tanga farms (with 2.10 and 1.48 mg/kg, respectively). These results might be due to the fact that Mazimbu farm were applying manure and industrial fertilizer, while other farms did not. The results agree with Bekunda et at (2004) who stated that Phosphorus is a less mobile nutrient in soils, causing it to accumulate more in soils where mineral fertilizers are applied.  Adequate Phosphorus in soils of Mazimbu farms is reflected in spikelet germination percentage where Mazimbu seeds showed a bit better results as compared to other farms.  According to Griffith  (2012), Phosphorus nutrient is essential for the general health and vigor of all plants. Some specific growth factors that have been associated with the presence of the phosphorus nutrient are to stimulate root development, increase inflorescence stalk and stem strength, improved flower formation and seed production. According to Moberg (2000), soil fertility ratings of Potassium were observed to be at medium levels of 0.61 and 0.39 me/100 g at Mazimbu and Tanga farms, indicating optimum levels of available potassium for plants. However, the low level was observed at Vikuge farm soils (0.22 me/100g). Soils of Vikuge farm were observed to be more deficient in all macronutrients due to continuous cultivation without application of fertilizers showed by age of the sward for seed production which was older compared to other farms (Table 2).

Conclusion and Recommendations

• The results show that, the quality of Cenchrus ciliaris seeds from three farms was low according to seed quality Standards for declared seed quality (FAO 1993).  Among other factors soil fertility important for plants wellbeing as per soil analysis was at low levels in all farms. Thus, these farms need soil fertility adjustment through fertilizer application basing on soil fertility recommendations. Age of the sward seem probably to be also a  factor affecting viability of seeds,  seed production in the farm with sward above four years resulted  in poor quality seeds. It is recommended that farms conduct seed testing (for viability and health) each year from newly established to old vegetation to monitor quality of seeds each year and batches produced. However further studies on fertilizer rates, dry season irrigation, row spacing and seed heath challenges are required to bring more understanding on seed production in this sub humid agro-ecological zone of Tanzania.

Acknowledgements

The authors extend their sincere thanks to the Ministry of Livestock & Fisheries Development of Tanzania for its financial support for this study.

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Received 20 December 2012; Accepted 10 April 2013; Published 1 May 2013

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