**1. Introduction**

Sub-Saharan livestock production is increasingly constrained by feed shortage, both in quantity and quality [1]. Livestock production can be improved through good management of natural grasslands and introduction of improved fodder species [2] with the supply of fertilizer and water to maintain high productivity that the high cost and low availability of good quality animal feed is a critical constraint to increasing productivity of livestock in dairy farms and feedlots, improved family and specialized poultry, and smallholder mixed crop-livestock and extensive livestock production systems [1].

Nutrient dynamics in tropical soils sustaining forage grasses are still poorly understood [3]. Lack of nutrients, inadequate management of pastures, and inappropriate cultural practices are responsible for pasture degradation. Applying fertilizers in large quantities increase the productivity of grasslands [4]. Low nitrogen availability has been identified as a major cause of degradation of tropical pastures [5] and the constant removal of forage without proper supply of nutrients extracted by plants emphasizes the problems of grazing land degradation [6]. The application of nitrogen and phosphorus has proved to be effective in maximizing the production of dry matter [7] and nutritional status [8] of grasses.

Grazing lands in Ethiopia play great role in livestock production. However, grazing land degradation in Ethiopia is a serious problem [9]. Since a few decades ago, the country is not only known for the severity of grazing land degradation and related problems, but also for concerted efforts to confront the problems using land rehabilitation measures such as enclosures [10]. Enclosures have been widely established particularly in the midland and highland agro-ecologies. They are among the green spots with considerable species diversity and higher biomass production compared the unclosed areas [11] .

Nitrogen and phosphorus fertilizers have been used for long period of time in agricultural system [12]. Nitrogen fertilizer application improves above ground biomass of any plant crops [13]. Phosphorus improves the growth of legumes and plant species composition generally and a Poaceae pasture in specific [14]. Nitrogen and phosuphorus fertilizers combined application could improve the aboveground plant biomass [15] and have positive effects on composition diversity of plant species [16]. Primary mineral fertilizers such as nitrogen, phosphorus, and sulfur etc. are favoring the growth of plants through improving soil fertility [17]. Though enclosures produced better biomass than the freely grazed areas, production is still limited. This probably is because of limited plants growth related to nutrient deficiency. Addition of nitrogen and sulfur fertilizers increased shoot dry matter production in the second and third growth of forage plants [3]. Nitrogen availability maximizes plant growth and productivity [6]. Nitrogen deficiency in the grazing areas of Ethiopian highlands due to land degradation was, which probably could be the leading constraint for limited plant growth and reduced biomass yield, affecting crop production [18]. Hence, application of nitrogen and phosphorus with sulfur seems imperative to enhance plant growth and increase herbage biomass production. The first and foremost beneficiaries of the research findings are small holder farmers, policy makers, researchers and NGOs. The hypothesis of the study was fertilizing grazing lands improve the herbage biomass and economic feasibility and applicability of grazing lands under small holder farmers condition. Therefore, this study was planned to evaluate top dressing of grazing lands in terms of biological gain and assess economic gain and the applicability of pasture fertilization under smallholder private or communal grazing lands.

## **2. Materials and methods**

#### **2.1 Study area**

The study was conducted at the highland of Chosha kebele, Bonke district, Gamo Gofa zone, Southern Ethiopia (**Figure 1**). The altitude of the area is 2350 meter above sea level with annual average rainfall of 2017.06 mm and mean daily temperature ranging between 10.0–23.3°C (**Figure 2**). The rainfall is bi-modal with the winter rain (short rains) occurring in March to May and the summer (main season) rains lasting from June to October. Major crops such as potato, wheat, barley,

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

**Figure 1.** *Location map of experimental site.*

**Figure 2.**

*Rainfall, maximum and minimum temperature of experimental season and ten years average in the location.*

bean, onion, paper, cabbage, fruits are grown widely in the study area according to site observation and district report. Natural pasture is the major feed source in the area and farmers using cut and carry system of livestock feeding mainly because of shortage of farming and grazing land. The soil of study area is characterized as strongly acidic with pH < 5.0, low organic carbon contents which ranged from 0.25% to 1.05%, moderate calcium carbonate with 0.88%, high organic matter with 13.56%, low catain exchange capacity with 16.69 cmolc/kg and sandy-loam [19].
