Effect of phosphorus fertilizer application on the growth traits and grain yield of cowpea
Abstract
Phosphorus is one of the major essential nutrient elements required in adequate quantity in
available form for proper growth and development of crops. However, phosphorus is one of the
most limiting nutrient elements in tropical soils for the production of various crops, especially
leguminous crops. This study was carried out at Makerere University Agricultural Research
Institute Kabanyolo (MUARIK) to determine the effect of phosphorus fertilizer on the growth
and yield performance of cowpea. The experimental design was a randomized complete block
design with three replications. The treatments comprised a control where phosphorus fertilizer
was not applied, 20, 40, and 60 kg P/ha. Data were collected on growth traits namely, number of
leaves per plant, number of branches per plant, number of root nodules, plant height, fresh
weight of the root, and fresh weight of the aboveground biomass, as well as yield performance
traits, namely the number of pods per plant, number of seeds per pod, pod length, the weight of 100
grains per plot and grain yield per plot. The results showed that the gradual increase in
phosphorus fertilizer application resulted in a gradual increase in plant height and several
branches, with the rate of 40 kg P/ha giving significant (P<0.05) increases in plant height and
number of branches when compared with the control. The number of root nodules and the above-ground biomass increased gradually, becoming significantly (P<0.05) higher than in the control
at the application rate of 60 kg P/ha. The phosphorus application rate of 40 kg P/ha produced a
significantly higher number of pods per plant and the number of seeds per pod when compared with
the control. Grain yield increased with a gradual increase in P levels, and the rates of 40 and 60 kg
P/ha produced significantly higher grain yields than the control. Based on the results, it was
concluded that the application of phosphorus fertilizer at the rate of 40 kg/ha is suitable for
optimum growth and grain production of cowpea. It was recommended that farmers growing
cowpea should apply phosphorus fertilizer at the rate of 40 kg/ha and above to obtain
significant increases in cowpea grain yields. However, further research should be conducted
using higher application rates of phosphorus fertilizer to determine the rate of
application that would optimize the grain yields of cowpea.