Effect of partial root zone drying and deficit irrigation on nitrogen and phosphorus uptake in potato

Abstract

Better understanding of the effects of deficit irrigation regimes on phosphorus (P) and nitrogen (N) uptake dynamics is necessary for sustainable water, P and N management. The effects of full (FI), deficit (DI) and partial root-zone drying (PRD) irrigation on potato P and N uptake with P fertilization (P1) or without (P0) were investigated in two split-root pot experiments in a soil with low plant available P. Under FI, the plants were irrigated to pot water holding capacity while under DI and PRD, 70% of the water amount of FI was applied on either both or one side of the pots, respectively. During potato growth, plant P uptake increased while P concentration decreased at P1 and was almost constant at P0. PRD and DI reduced plants P uptake to a same extent, ca. 22% compared to FI at P1, while at P0, plants P uptake was similar for the three irrigation treatments. Soil P transport to the root surface by diffusion was similar under DI and PRD. DI treatments had higher soil microbial biomass P, water soluble P, root biomass and leaf water potential than PRD treatments, while PRD treatments had higher plant N:P ratios than DI treatments and higher root secretion of acid phosphatases that may have compensated for the lower level of water soluble P. N was immobilized in soil in all the treatments. Plant N uptake under PRD was higher than DI at both P levels, which could be explained by the higher microbial biomass and N-immobilization under DI. In conclusion, when same amount of water was used, PRD was superior to DI in terms of N uptake, but not P uptake. Challenges remain how to maintain crop yield and P uptake under reduced irrigation regimes. Utilization of water and N fertilizer was low when the soil was deficient in P.