ABSTRACT
A field experiment was conducted in the early growing season (April- July) of 2014 at the Teaching and Research farm of the University of Benin. The objective of the study was to evaluate the effects of three rates (0, 120, 240 kg ha-1) of NPK fertilizer and 2 plant spacings (30 x 30 cm and 30 x 40 cm) on the growth and herbage yield of two pasture grasses (Brachiaria decumbens and Digitaria decumbens). The 12 factorial treatments were laid out in a randomized complete block design (RCBD) and replicated 3 times. Rooted propagules of uniform height (10 cm) were transplanted into the plots based on treatments. Fertilizer was applied at 6 weeks after transplanting to the respective plots when the seedlings had established. Variables measured at 6, 12 and 18 weeks after transplanting were sward height (cm), number of tillers and fresh herbage yield (kg ha-1). All variables decreased in values between 12 and 18 WAT. However, at 12 WAT Brachiaria decumbens furnished significantly heavier fresh herbage yield ( 5.9 t ha-1) compared to Digitaria decumbens (5.3 t ha-1). Generally, the variables increased as fertilizer application increased. The trend for fresh herbage yield was 240 kg ha-1 NPK (7.6 t ha-1) > 120 kg ha-1 NPK ( 6.1 t ha-1) > 0 kg ha-1 NPK (3.1 t ha-1). Brachiaria decumbens obtained the significantly ( p < 0.05) tallest sward height (120.2 cm) at 12 WAT and the heighest number of tillers (52.8) at 18 WAT with the highest rate of fertilizer application. At 12 WAT, the wider plant spacing (30 x 40 cm) furnished significantly (P < 0.05) more tillers (45.1) than the narrow spacing (30 x 30 cm). In conclusion, Brachiaria decumbens exhibited better growth and yield attributes than Digitaria decumbens. Fertilizer application exhibited a linear effect for all the variables. The wider spaced plants produced more tillers than the closely spaced plants. The relatively high fresh herbage yields recorded by both grasses imply they can provide sufficient fodder for numerous ruminant livestock.
CHAPTER ONE
INTRODUCTION
Nigerian’s 101 million herd of domestic ruminants (Fed Ministry of Agriculture and Water Resources, 2008) depend on forage and fodder crops for their productivity. It is estimated that only a dismal 3% of the total livestock are reared on improved pastures (Okorie and Sanda , 1992). Similarly, an extensive portion of the 32.42 million hectres of grazing land in Nigeria are undeveloped and composed of low yielding indigenous forage species with low quality (Shiawoya and Tsado, 2011). Subsequently,these grazing reserves will be developed through direct seeding or transplanting of improved pasture species. (Bogdan, 1977).
The humid zone of Nigeria which has a rainy season of 8 months is potentially a forage production centre (Ezenwa and Aken’Ova, 1998). Although the humid zone of Nigeria was not amajor cattle production area because of the prevalence of tsetse fly with its associated disease (trypanosomiasis) problem, the trend has changed in recent years. The encroachment of the derived savanna due to land clearing coupled with population explosion are instrumental to this change. There has been a rapid increase in the population of non-trypanotolerant white Fulani zebu and trypanotolerant breeds (Ndama and Muturu) in southern Nigeria.
Generally, the cultivation of forage crops for feeding livestock is not a common activity in Nigeria. For this reason, most improved pasture grasses have only been subjected to agronomic evaluations inside research institutes and few modern livestock farms in the conventional livestock producing region of northern Nigeria. Bracharia decumbens and Digitaria decumbens are relatively new pasture grasses that were recently introduced into the humid of Nigeria (Ogedegbe, personal communication). Generally, low nitrogen supply hampers and degrades pastures (Werner, 1994). Fertilizer application increases both dry matter and crude protein yields of forage grasses (Harding, 2005). Plant spacing significantly affected the survivability, crude protein and herbage yield of elephant grass (Akinola, 1982). Furthermore, pasture grasses thrive under moderately humid environments close spacing (20 x 20 cm) of rooted sprigs of signal grass established faster than widely spread sprigs (Okeagu and Agushi, 1990) which may be less prone to disease outbreaks (Humphreys, 1999). For the aforementioned reasons, it is necessary to evaluate pasture grasses under humid environmental conditions in order to deduce an appropriate agronomic system for their management. The objectives of the study were:
- To evaluate the influence of NPK fertilizer on the growth and herbage yield of two pasture grasses(Brachiaria decumbens and Digitaria decumbens)
- To evaluate the effect of spacing on the growth and herbage yield of two pasture grasses(Brachiaria decumbens and Digitaria decumbens)
