Effect of partial root-zone drying irrigation (PRDI) on the biomass, water productivity and carbon, nitrogen and phosphorus allocations in different organs of alfalfa

Partial root-zone drying irrigation (PRDI) can influence carbon (C), nitrogen (N), and P (phosphorus) allocations in annual crop plants. This study consisted of a two-factorial split-plot field experiment conducted on Huanghua farmland in western China, and it was focused on investigating the effects of PRDI on the biomass; water productivity; and C, N and P allocations in a perennial plant (alfalfa) from 2016-2017. The two factors were the irrigation mode (PRDI and conventional furrow irrigation (CFI)) and irrigation volume (70 %-I-1, 85 %-I-2, 100 %-I-3 and 115 %-I-4 of the alfalfa water requirement), in which the irrigation mode was the primary plot and the irrigation volume was the subplot. This study showed that PRDI decreased the alfalfa leaf biomass and increased the alfalfa root, stem biomass and water productivity but that it had no effect on the alfalfa shoot biomass at the end of the vegetative growth period in 2016 and 2017. PRDI increased the C and P concentrations in the roots and the N concentration in the roots, stems and leaves, and it led more C and P to be allocated to the roots and more N to be allocated to the leaves in 2016 and 2017. These results implied that C, N, and P allocation changes in different organs induced by PRDI may be one of the possible ways for alfalfa plants to adapt to the changing environmental conditions caused by PRDI.