Gas exchange and millet phytomass under organic fertilization and graywater irrigation¹

Trocas gasosas e fitomassa do milheto sob adubação orgânica e irrigado com água cinza

HIGHLIGHTS:

Higher gas exchange values during the initial growth stage are associated with significant phytomass accumulation in pearl millet.

Graywater did not provide enough nutrients to boost the millet phytomass accumulation.

Fertilization with bovine manure favored an increase in basal tiller mass.

ABSTRACT

Graywater is an alternative method to increase the water supply for agricultural production in semi-arid regions. The objective of this study was to evaluate the effects of different irrigation depths of graywater on the gas exchanges and phytomass of millet plants with and without organic fertilization. The research was conducted under greenhouse conditions in Serra Talhada municipality in semiarid region of Brazil, in a randomized complete block design with a factorial (4 × 2 + 1) plot and three replicates. The first factor corresponded to graywater irrigation depth equivalent to 25, 50, 75 and 100% of the available water content of the soil, and the second factor was the addition of bovine manure as fertilizer (0 and 34 Mg ha^-1), and a control (irrigation with low-salinity water). Irrigation with graywater effluent did not promote adverse effects on gas exchanges and phytomass accumulation; however, it also did not provide enough nutrients to promote increase in these variables. The reduction in irrigation depth caused a decrease in gas exchange from 45 days after the application of the treatments. The basal tiller mass was the most favored plant component due to organic fertilization.

Key words:
Pennisetum glaucum; irrigation water depths; bovine manure; wastewater