**2.2 Treatments and experimental design**

The fertilizer treatments for the study were T1 = control, T2 = urea and T3 = combined urea and NPS in both summer and winter major cropping seasons of Ethiopia. The amount of urea and NPS that were used in the experiment was 150 kg; and 110 and 100 kg per ha for T2 and T3, respectively. Factorial combination of two seasons and 3 fertilizer treatments laid out in RCBD with four

replications. The plot size consisted of an area of 400 m2 (20m x 20 m) and the space between plots was 3 m. Nitrogen fertilizer applied in the form of urea as a split dressing i.e., one-third at about 7 days of the first rain and two-thirds after about a month of the first rain and P fertilizer in the form of NPS applied at about 7 days of the first rain together with the nitrogen applied at 7 days after the first rain. The trial is replicated in winter and summer seasons with fertilizer application in March for winter and in June for summer. The fertilizers applied manually in the field determined for experiment.

#### **2.3 Data collection and sampling procedures**

#### *2.3.1 Forage yield*

Herbage biomass was measured as the herbaceous vegetation harvested at ground level using manual sickle from five 0.5 m quadrates (four at the corner and one at the center of the 10 m x10m plots) using sickle in each of the 100m2 plots. Fresh biomass weighed immediately using weighing scale of 0.1 g. Then, a subsample of 15–20% of the total weight was separated and put into a paper bag for dry matter determination and oven dried at 105°C for 24 hours.

#### *2.3.2 Species composition*

Species composition was determined by using quadrate count method and identified in the field with farmers for local name and taxonomic classification. Species that were difficult to identify in the field recorded and collected to herbarium for identification.

#### *2.3.3 Economic considerations*

Partial budget analysis was performed to evaluate the economic advantage of fertilization by using the procedure of Upton (1979). The partial budget analysis involves calculation of the variable costs and benefits. The benefits are calculated based on market value of green or cured grass for all expenses recorded at the beginning of the study.

The amount of herbage obtained used to calculate the income earned (TR). The calculation of the variable costs and the expenditures incurred on various activities were taken into consideration.

The partial budget method measured profit or losses, which is the net benefits or differences between gains and losses for the proposed change and includes calculating net return (NR), i.e., the amount of money left when total variable costs (TVC) are subtracted from the total returns (TR):

$$\text{NR} = \text{TR} - \text{TVC} \tag{1}$$

Total variable costs included the costs of all inputs that change due to the change in production technology. The change in net return (ΔNR) calculated by the difference between the change in total return (Δ TR) and the change in total variable cost (Δ TVC), and this is used as a reference standard for decision on the adoption of a new technology.

$$
\Delta \text{NR} = \Delta T \text{R} - \Delta T \text{VC} \tag{2}
$$

*Top Dressing of Fertilizers: A Way Forward for Boosting Productivity and Economic Viability… DOI: http://dx.doi.org/10.5772/intechopen.99094*

The marginal rate of return (MRR) measured the increase in net income (Δ NR) associated with each additional unit of expenditure (Δ TVC). This is expressed by percentage

$$MRR\% = \frac{\Delta NR}{\Delta TVC} \ast 100\tag{3}$$

### *2.3.4 Statistical analyses*

The experimental data was subjected to analysis of variance using the General Linear Model Procedure of Genstat statsitcal software [20]. Tukey HSD test applied for mean comparisons and statistically significant differences were accepted at P < 0.05.

### **3. Results and discussions**

#### **3.1 Herbage biomass**

For the present experiment dry matter yield significantly (P < 0.001) varied among treatments and higher results were obtained from combination of urea and NPS followed by urea than the control one (**Figure 3**). This may be due to the application of nitrogen, phosphorus and sulfur in the form of urea and blended NPS fastened the growth of grasses, legumes and other species. Nitrogen Fertilizer application increased dry matter yield. Dry matter yield in summer was by far greater than in winter (**Figure 3**) that may be due to moisture stress in winter season which could demonstrate that the growth of pastures improved in rainy season than dry. Dry matter accumulation is physiological index related to photosynthesis of leaves in which legumes respond less to N than grasses; grass dominant pastures well responded to N [21]. The increase in the proportion of grass reflects the role of nitrogen fertilizer in influencing the grass-legume botanical composition in favor of

**Figure 3.** *Dry matter yield (t/ha) as affected by fertilizer application.*

grass growth. NPS fertilizer application improved the dry matter yield production of Napier grass in Ethiopia [7] report is in line with the present study. Nitrogen and Phosphorus fertilizers are vital to plant growth and found in every living plant cell and total dry matter yield increment due to nitrogen, phosphorus and potassium fertilizers application reported previously for desho grass production [22]. Nitrogen and phosphorus fertilizers application also improved the growth and crud yield of cauliflower [23]. And also another similar report stated that proper nitrogen and sulfur fertilizer application promotes grass production by improving uptake of nutrients and the dynamics of the organic and mineral fractions in tropical soil [3].
