Abstract
This study is to test how seedlings (vegetative) and large plants (reproductive) of an oilseed crop (Plukenetia volubilis) responded to regulated deficit irrigation techniques (conventional deficit irrigation, DI; alternative partial root-zone irrigation, APRI) in a tropical humid monsoon area. Seedlings were more sensitive to water deficit than large plants. Although APRI did better than DI in saving water for both seedlings and large plants at the same amount of irrigation, full irrigation (FI) is optimal for faster seedling growth at the expense of water-use efficiency (WUE). The seed number per unit area was responsible for the total seed oil yield, largely depending on the active process of carbon and nitrogen storages at the whole-plant level. The magnitude of the increase in total seed and seed oil yield by fertilization was similar under different irrigation regimes. Compared with FI, DI can save water, but reduced the total seed yield and had lower agronomic nutrient-use efficiency (NUEagr); whereas APRI had similar total seed yield and NUEagr, but reduced water use greatly. Although the dual goal of increasing the yield and saving water was not compatible, maintaining a high yield and NUEagr at the cost of WUE is recommended for P. volubilis plantation in t he water-rich areas.
Highlights
Water stress is a major limitation for crop production in many areas of the world since it reduces cell growth rate, and limits the crops’ reproductive process[1]
Except for leaf N concentration, leaf and plant growth traits of P. volubilis were greatly influenced by regulated deficit irrigation (RDI) (Table 1)
The net photosynthetic rate (Pn), stomatal conductance (Gs,) transpiration rate (Tr), total biomass, leaf area index (LAI), specific leaf area (SLA) and photosynthetic nitrogen-use efficiency (PNUE) decreased, whereas root mass fraction (RMF), root/shoot (R/S) ratio and WUEi increased with decreasing amount of irrigation water
Summary
Water stress is a major limitation for crop production in many areas of the world since it reduces cell growth rate, and limits the crops’ reproductive process[1]. 0.46b 226.70ab 25.39b leaf-air water VPD during leaf expansion in the humid areas may hamper stomatal responsiveness to closing stimuli with a genotype-dependent effect[13] It still remains debatable if the water-saving techniques could achieve the dual goal of increasing crop yield and saving water, especially for the sparsely planted woody crops[14,15]. The objectives of this study are the following: (1) to evaluate the sensitiveness of plant growth in response to water stress between seedlings at the vegetative stage and large plants at the reproductive stage; (2) to determine if irrigation regimes could synergistically interact with fertilization rates to increase yield, WUE and NUE of P. volubilis plants in the field and (3) to determine the combination of RDI and fertilization to optimize seed oil yield and resource-use efficiency
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