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More than 70% of global rice production depends on irrigation water, which has brought on a progressive reduction in the groundwater table. Further groundwater withdrawal are unsustainable for future rice production. Sustainable rice production calls for the use of resource-saving and environmentally friendly rice varieties. This study investigated the morphological and physiological mechanisms of biomass and tissue phosphorus accumulation in a water-saving and drought-resistance rice variety (Hanyou73) and a normal paddy rice variety (Hyou518) under different water management regimes. The two rice cultivars were grown in pot experiments carried out with factorial combinations of three water regimes, conventional irrigation (high irrigation rate, HR), 60% of conventional irrigation (medium irrigation rate, MR), and 20% of conventional irrigation (low irrigation rate, LR) for four-years. While the grain yield of Hanyou73 was similar as Hyou518 under HR, it was significantly higher than Hyou518 under MR and LR. Under deficit irrigation, the tissue-specific biomass of Hanyou73 was higher than that of Hyou518, and the total P accumulation of Hanyou73 was 70% greater than that of Hyou518. Meanwhile, the root growth, root oxidation activity, and absorption area of Hanyou73 under the MR and LR treatments were significantly higher than those of Hyou518. Analysis of root exudate metabolites revealed an abundance of organic acids produced by the Hanyou73 roots under, which may account for its higher P uptake. Overall, the findings of this study indicate that Hanyou73 promoted P uptake to maintain higher yields under deficit irrigation. The higher P uptake by Hanyou73 may be related to its altered root physiology, which may be the mechanism by which Hanyou73 adapts to water saving irrigation conditions and maintains its yield traits.

We introduce a new class of games called the networked common goods game (NCGG), which generalizes the well-known common goods game. We focus on a fairly general subclass of the game where each agent's utility functions are the same across all goods the agent is entitled to and satisfy certain natural properties (diminishing return and smoothness). We give a comprehensive set of technical results listed as follows. * We show the optimization problem faced by a single agent can be solved efficiently in this subclass. The discrete version of the problem is however NP-hard but admits an fully polynomial time approximation scheme (FPTAS). * We show uniqueness results of pure strategy Nash equilibrium of NCGG, and that the equilibrium is fully characterized by the structure of the network and independent of the choices and combinations of agent utility functions. * We show NCGG is a potential game, and give an implementation of best/better response Nash dynamics that lead to fast convergence to an $\epsilon$-approximate pure strategy Nash equilibrium. * Lastly, we show the price of anarchy of NCGG can be as large as $\Omega(n^{1-\epsilon})$ (for any $\epsilon>0$), which means selfish behavior in NCGG can lead to extremely inefficient social outcomes.