Date Published: March 27, 2019
Publisher: Public Library of Science
Author(s): Jie Liu, Tiantian Hu, Puyu Feng, Li Wang, Shuohuan Yang, Ricardo Aroca.
Faced with the scarcity of water resource and irrational fertilizer use, it is highly important to supply plants with water and fertilizer at desiderated stages to improve yield with high water use efficiency (WUE). A pot experiment was conducted to investigate the effects of growth stage-specific water deficiency and potassium (K) fertilization on tomato yield and WUE. The entire growing season of tomato was divided into 5 stages: vegetative growth stage (VG), flowering and fruit setting stage (FS), early fruit growth stage (FG), fruit development stage (FD) and fruit maturity stage (FM). Three soil moisture (W) and three K fertilization levels were set up. W levels included W1, W2 and W3, indicating that soil water was maintained at 60–70% field capacity, 70–80% field capacity, and 80–90% field capacity, respectively. K levels included K1, K2 and K3, indicating that 0 g K2O per kg soil, 0.46 g K2O per kg soil and 0.92 g K2O per kg soil was applied. All combinations of the three W and three K levels were solely imposed at each of the five growth stages, for other four stages, plants were watered to 80–90% field capacity without K fertilizer (W3K1). The permanent W3K1 over the entire growth stage was taken as control (CK). The results showed that W deficiency imposed at all stages significantly affected tomato yield (P<0.01), except for VG stage in which W deficiency did not cause yield loss. K fertilization level during FS or FM stage had a significant effect on yield (P<0.01). A significant interaction effect of W and K on yield was only observed during FM stage. For WUE, significant effect of W deficiency at FS, FD and FM stages were observed, and a significant effect of K levels at FS, FD and FM stages was observed. Specifically, K fertilization was necessary during specific growth stage of tomato (i.e. FS and FM). During FS stage, even if a sufficient water supply seems necessary, a deficit irrigation with K fertilization could be applied as K fertilization could alleviate the negative effect of soil water deficit, however, excess of K fertilization during FM stage should be avoided to maintain tomato yield and WUE.
In large areas of tomato (Lycopersicon esculentum) cultivation, rainfall could not meet crop water needs, and surface irrigation is mainly adopted by farmers in practice, which may lead to water waste . Meanwhile, too much fertilizer applied in pursuit of high yield resulted in lower quality , soil salinization and groundwater contamination [3, 4]. Therefore, a better understanding of plant periodical response to soil moisture and fertilizer is highly important to water and fertilizer management in practice. To cope with water scarcity, which is the primary constraint for high crop yields in many arid areas, deficit irrigation (DI) has been widely adopted [5, 6]. DI allows the crop to experience a certain extent of water stress either by applying less irrigation during the entire crop cycle or by withdrawing irrigation at certain stages, without compromising yield too much. DI is demonstrated to increase water productivity and optimize water use efficiency (WUE) [7–9].
Our study shows that the effects of soil water deficit and potassium fertilizer on tomato yield and water use efficiency depended on tomato growth stages. Soil moisture and potassium fertilizer were generally not limited factors during vegetative growth stage, so deficit irrigation without K fertilizer at this stage could be recommended. Potassium fertilizer could alleviate the negative effect of water stress during flower and fruit setting stage. Sufficient water supply during fruit development and maturity stage was essential for tomato yield. During fruit maturity stage tomato yield was enhanced by moderate potassium fertilizer, while decreased by excess application, indicating moderate level of potassium fertilizer during fruit maturity stage was needed.