Physiological and productivity evaluation of Napier grass ('Pennisetum purpureum' Schumach.) cultivars under variable water supply, temperature and carbon dioxide conditions

Abstract

Grasses have always been and will continue to be the most important resources for humans and their domestic animals. This study focused on one species of grass, Napier ('Pennisetum purpureum' Schumach.), that is valuable for fodder in both tropical and sub-tropical regions of the world. Napier grass cultivation is likely to increase, especially in east Africa, associated with the increase in human population coupled with a growing demand for livestock products. However, because the present arable land is fully committed, cultivation is expanding into marginal areas. These areas are usually characterised by high temperatures and reduced precipitation, likely to be adversely impacted by global warming associated with increased atmospheric CO₂ levels. This study was designed to increase understanding about how different Napier grass provenances respond to reduced water supply through rainfall and rising temperatures and their impacts on herbage productivity and quality. Such understanding would guide recommendations for farmers in these marginal areas to improve Napier grass management. Techiniques in tissue water status and gas exchange were applied to assess if they could be effective predictors of herbage yield and quality in Napier grass when subjected to water-stress and high temperature stress. The project was implemented in three phases: (1) a glasshouse study that tested the physiological techniques on two Australian cultivars, (2) field trials that tested the techniques on 10 acessions of Napier grass in two contrasting environments in Kenya, and (3) glasshouse study comparing Napier grass (C₄) with a common reed (C₃) subjected to water and heats tress and exposed to high atmospheric CO₂ concentrations.