Sorghum (Sorghum bicolar (L.) Moench) is an important staple
food grain among many smallholder farmers of the Nigerian savanna (Ofor et al.,
2009). It occupies about 44% of the total land area devoted to cereals in
Nigeria (Ajeibe et al., 2010). The land area put into cultivation of sorghum in
Nigeria is 6.7 million hectares (FMARD, 2012b).
Decline in yield has been identified as major constraint to
sorghum production. Average yield is estimated at 0.6-1.7 tons per hectare
against potential yield of 4.0-5.0 tons per hectare of sorghum (FMARD, 2012b).
The yield gap is attributed to poor inherent soil fertility and low fertilizer
use. (Vanlauwe and Giller, 2006). Smallholder farmers apply little to no fertilizer
to their land due to socioeconomic factors including timely access to
fertilizer (SSA-CP, 2005). Improper types of fertilizers, ineffective extension
system and inappropriate fertilizer recommendation which limit the efficiency
of fertilizer use reduce farmer‟s income and increase poverty and food
insecurity in the Northern Guinea Savanna of Nigeria (SSA-CP, 2005).
Nitrogen use efficiency (NUE) is important in developing
fertilizer recommendations for profitability and environmental sustainability
(Kaizzi et al., 2012). Low nitrogen use efficiency in crop production is due to
excess application of N. Deficiency of phosphorus (P) and other essential
nutrients limit crop growth due to biotic and abiotic factors (Bekuda et al.,
2007; Kaizzi et al., 2012). Several attempts to provide fertilizer
recommendations tosmallholder farmers often lead to inappropriate fertilizer
rates that lower the NUE of crops.
1.1 Justification of the Study
Current fertilizer recommendations are aimed at maximizing
yield rather than profit. The fertilizer rate needed to maximize net returns is
a function of fertilizer cost relative to grain prices as the fertilizer prices
increase relative to the prices, the economic optimal rate (EOR) is expected to
decrease. Therefore, they need to maximize net returns for a given amount of
money they have to invest in fertilizer which can be maximized by identifying
the right combinations of nutrient, and application rate that will give highest
value to cost ratio (VCR).
1.3 Objective of the Study
The general objective of this study was to provide
recommendations for optimizing crop yield and profit from fertilizer use for
financially constraint and small holder sorghum farmers in the northern guinea
savanna zone of Nigeria. The specific objectives are:
To evaluate the yield response of sorghum to N, P and
potassium (K) at the selected sites in the Northern Guinea Savanna of Nigeria.
To determine the economically optimal nutrient rate for N, P
and K and the corresponding value to cost ratio (VCR) at different fertilizer
cost to grain price ratio.
To determine the N use efficiency (NUE) of sorghum at the
selected sites in the Northern Guinea Savanna of Nigeria.