Growth Rate and Biomass Accumulation of Forage Sorghum (Sorghum almum), Congo grass (Brachiaria ruziziensis) and Rhodes grass (Chloris gayana)

 ABSTRACT

Many grasses have played prominent roles in forage research and livestock production in Nigeria. Grasses possess two main photosynthetic pathways: the C3 pathway that is typical of most plants and a specialized C4 pathway that minimizes photorespiration and thus increases photosynthetic performance in high-temperature and/ or low- CO2 environments.

Rhodes grass (Chloris gayana) is a perennial grass of tropical and subtropical Africa where it remained one of the main C4 forage grasses.

Forage Sorghum (Sorghum a/mum) originated in Argentina and the latitudinal range of the grass is 25°N to 30°S. It can be found at elevations between sea level and 700m.

Congo grass (Brachiaria ruziziensis) has been widely used in crop rotation and crop-livestock integrated systems in the world because of its good adaptation to low fertility soils, high yield potential, and good forage quality.

This research is aimed at developing a model that can correctly predict the growth rate and also the biomass accumulation of Sorghum a/mum, Brachiaria ruziziensis and Chloris gayana.

The experiment was conducted at the screen-house of the Faculty of Agriculture, Federal University, Oye-Ekiti, Ikole campus with Latitude - N 07° 48.308, Longitude - E 005° 29.573 and 548.4m above ground level.

The planting was done using completely randomized design (CRD) in 3-rows with 4 replicates of 8 pots of each grass species and a spacing of Im long apart was applied between each bed.

 The soil used for this study contained a high organic matter before planting (32.81) and after harvesting was completed (I8.70). The soil used in planting belonged to the Loam soil category.

The highest growing grass was Sorghum a/mum throughout the period of carrying out this experiment.

The sward heights of the three grass species were not significant from each other.

The highest crude protein content was observed in the first cuttings (2nd week) while Sorghum a/mum had the highest crude protein content. Crude protein was found to decrease linearly as the grasses grow. At p < 0.05; Sorghum a/mum had more protein content for the study period than Chloris gayana and Brachiaria ruziziensis at both weeks 2 (12.11, 7.71 and 4.97), 4 (10.34, 5.77 and 3.52), 6 (8.61, 4.52 and 2.95) and 8 (9.40, 2.57 and 0.84)

The crude fibre content of the three grass species increased as the grasses grew; the highest fibre content was observed in the 8tl1 week of cutting due to encrustation of lignin in them as the grasses matured giving the impression that both the fibre and protein contents of the grasses are inversely related.

The crude Ash content varied between the three grass species and the times of cutting. Ash contains all the important nutritional ingredients especially minerals, both micro and macronutrients, which are very important for the normal physiological functions of the animal's body.

The moisture content varied between the grass species and the times of cutting; Grass with lowest moisture content could store for a longer time without spoilage.

The Crude fat content decreased significantly from the second week to the eighth week.

The growth rate of the grasses were observed throughout the course of undertaking this study and the varietal differences were observed with Sorghum a/mum the fastest.

The Biomass accumulation observed yielded between 10.11- 21.97% while the growth rate of the grasses observed was 68.81 - 94.98%.

Keywords: Sorghum a/mum, Brach/aria ruziziensis, Chloris gayana, Growth rate, Biomass, Grass Growth model, Crude protein, Crude Fibre, Crude Ash, Crude Fat, Moisture.