The effect of nitrogen fertilizer on Napier grass (Pennisetum purpureum) productivity: a meta-analysis

Abstract

Nitrogen fertilizer is the major nutrient required by grass for optimal growth and biomass production. The type
and dosage of nitrogen fertilizer application influence plant productivity. This research used a meta-analysis
approach aimed to assess how optimal N fertilizer dosage and types affect the productivity improvement of Napier
grass (Pennisetum purpureum). Search done in Elsevier, Scopus, Science Direct, JSTOR, ProQuest, and Web of
Science databases yielded 44 studies, of which 24 were suitable for the analysis. The dataset was collected between
1972 and 2022, and all experiments included a control treatment with no nitrogen fertilizer and a variety of forms
(organic or inorganic) that were evaluated herein for the productivity and nutritional contents of Napier grass. The
data were then subjected to meta-analysis using a mixed-effects model methodology, treating different doses or
forms of nitrogen fertilizer as fixed effects and various studies as random effects, with the p-value used as the
statistical model. The findings demonstrated that N fertilizer dosage influences (P<0.05) the total dry weight of
forage, leaf weight, plant height, N, P, Na production, and dry matter digestibility. Furthermore, the type of
inorganic fertilizer affects (P<0.05) the production of fresh Napier grass forage, leaf weight, and plant height but
has no significant impact (P>0.05) on other production parameters. In conclusion, the productivity of Napier grass
has the potential to increase effectively with higher doses of nitrogen fertilizer, with the optimal dosage at 1,493.31
kg N/ha/year. Both organic and inorganic types of N fertilizer show similar effects on most of the measured
variables.