Potassium fertilization increases water-use efficiency for stem biomass production without affecting intrinsic water-use efficiency in Eucalyptus grandis plantations

Abstract

Adaptive strategies to improve tree water-use efficiency (WUE) are required to meet the global demand for wood in a future drier climate. A large-scale throughfall exclusion experiment was set up in Brazil to study the interaction between water status and potassium (K) or sodium (Na) availability on the ecophysiology of Eucalyptus grandis trees. This experiment focused primarily on the changes in aboveground net primary production, stand water use, phloem sap and leaf d 13 C, net CO 2 assimilation and stomatal conductance. The correlations between these response variables were determined to gain insight into the factors controlling water-use efficiency in tropical eucalypt plantations. The intrinsic WUE in individual leaves (the ratio of net CO 2 assimilation to stomatal conductance) was estimated at a very short time scale from the leaf gas exchange. Sap flow measurements were carried out to assess the WUE for stemwood production (the ratio of wood biomass increment to stand water use). Averaged over the two water supply regimes, the stemwood biomass 3 years after planting was 173% higher in trees fertilized with K and 79% higher in trees fertilized with Na than in trees with no K and Na addition. Excluding 37% of the throughfall reduced stemwood production only for trees fertilized with K. Total canopy transpiration between 1 and 3 years after planting increased from about 750 to 1300 mm y À1 in response to K fertilization with a low influence of the water supply regime. K fertilization increased WUE for stemwood production by approx. 60% with or without throughfall exclusion. There was a strong positive correlation between phloem sap d 13 C and short-term leaf-level intrinsic WUE. Whatever the water and nutrient supply regime, the gas exchange WUE estimates were not correlated with WUE for stemwood production. Phloem sap d 13 C and leaf d 13 C were therefore not valuable proxies of WUE for stemwood production. The allocation pattern in response to nutrient and water supply appeared to be a major driver of WUE for stemwood production. In areas with very deep tropical soils and annual rainfall <1500 mm, our results suggest that breeding programs selecting the eucalypt clones with the highest growth rates tend to select the genotypes with the highest water-use efficiency for wood production.

Leaf, canopy and agronomic water‐use efficiency of field‐grown sugar beet in response to potassium fertilization

“…Similar results were obtained by Martineau et al. () for field‐grown maize under deficit irrigation, which stands in contradiction to studies reporting negative (Egilla, Davies, & Boutton, ; Pervez et al., ) or no (Battie‐Laclau et al., ; Jákli, Tränkner, Senbayram, & Dittert, ; Jákli et al., ) effects of reduced K availability on photosynthetic WUE Leaf . In this study, however, enhanced LAI in fertilized treatments provided a higher area for transpiration and resulted in a more efficient soil moisture absorption by roots compared to unfertilized treatments.…”

“…To our knowledge, no study is published concerning the effect of K availability on instantaneous WUE Canopy , but K fertilization had an ameliorating effect on WUE Leaf of field‐grown cotton (Pervez, Ashraf, & Makhdum, ). However, in eucalyptus, WUE Leaf was not affected by increased levels of K fertilization (Battie‐Laclau et al., ).…”

A systems biology view of wood formation in Eucalyptus grandis trees submitted to different potassium and water regimes

“…By contrast, genes in modules M10 and M11, involved in abiotic stress response and containing numerous genes of the ABA signaling pathway, were highly upregulated in either [−W+K] or [+W+K] treatments, suggesting that K‐fertilized trees were stressed independently of water availability. This finding is consistent with previous physiological studies showing that at the end of the dry season, K‐fertilized trees reached a higher level of water stress than K‐deficient trees (Battie‐Laclau et al ., ,b, ). This drought‐induced effect of K‐fertilization was linked to the enhancement of tree growth rate causing a faster decrease in soil water stocks during dry periods (Christina et al ., ).…”

“…Tree circumference (CBH) was measured at breast height (BH; 1.3 m above ground) every 15 d. Trunk biomass was quantified after cutting down the trees as described by Battie‐Laclau et al . (). An allometric equation allowing calculation of trunk biomass from CBH (González‐García et al ., ) was applied to predict biomass production per day (kg of dry matter d −1 per tree) for each tree, over the 3 months preceding sampling.…”

“…Recently, using a large‐scale through‐fall exclusion experiment, Battie‐Laclau et al . () showed that K fertilization improved water use efficiency and biomass production in Eucalyptus . However, during drought episodes, they noticed that the beneficial effect of K may not be sufficient to counterbalance the detrimental effect of increased water demand caused by higher growth rates of K‐fertilized trees (Battie‐Laclau et al ., ,b).…”