The effect of water table depth and salinity on growth dynamics of Rhodes grass (Chloris gayana

SEBASTIÁN CHIACCHIERA; NICOLAS BERTAM; EDITH TALEISNIK; ESTEBAN JOBBÁGY

CROP & PASTURE SCIENCE

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2016

1836-5795

Abstract. Depending on their depth, water tables can have a positive effect on plants, by supplying water; a negative effect, by creating waterlogged and/or saline conditions or a neutral effect. Rhodes grass (Chloris gayana), a tropical perennial forage adapted to saline soils, floods and droughts, is a viable choice for the lowlands in the Pampas region of Argentina. The effects of depth and salt concentration of the water table on the growth dynamics and biomass accumulation of Rhodes grass were quantified in a greenhouse experiment. The experiment consisted of 10 treatments, resulting from the factorial combination of five water table depths: 25, 75, 125, 175 and 225 cm, and two salt treatments (EC 1.4 dS.m-1 and 20.5 dS.m-1). The presence of non-saline water tables at a depth of 25 cm produced five times more biomass and showed an increase of equal magnitude in water consumption in comparison to situations with deeper water tables. The increase of shoot biomass was primarily explained by higher tiller and stolon density, which increased 3.3 and 7.7 times, respectively, at water tables which were 25 cm deep compared to deeper treatments. Furthermore, groundwater use efficiency was 30% higher in non-saline water tables at 25 cm depth. Similarly, at this depth, the length of the leaf blades were 50% higher compared to the deepest water tables evaluated. In contrast, the presence of saline water tables at 25 cm depth had a detrimental effect on the production of biomass and its components, whereas the effect at 125 cm and greater depths was neutral. Therefore, Rhodes grass is a species that can take advantage of the widespread shallow water table environments of the Pampas region as long as the salinity levels are low.