Promoting leaf K uptake, export and contribution to yield of spring maize through increasing planting density in Xinjiang

Objectives Planting density and potassium (K) are critical factors influencing the yield and quality of spring maize. Exploring the relationship between planting density and K absorption and transfer will provide a theoretical foundation for achieving high yield and quality of maize in Xinjiang.

Methods Field experiments with a split-plot experimental design were conducted in Xinyuan County of Xinjiang in 2015 and 2016. The main factor was maize cultivar and subplot factor was planting density. The two cultivars, Xianyu 335 and Zhengdan 958, were high-yielding hybrid cultivars and adapted to the local maize-growing climate. The planting density levels were conventional 60000 plants/hm² (M1) and high density 120000 plants/hm² (M2). At silking and maturity stages, the canopy leaves and stem nods of spring maize were sampled for determination of dry matter and potassium content. The accumulation and transfer characteristics of K were calculated afterwards.

Results Compared with M1, high planting density (M2) significantly increased yield of both cultivars, with the yield increases of 54.86% and 30.97% for Xianyu 335, and 36.86% and 23.94% for Zhengdan 958 in 2015 and 2016, respectively. M2 enhanced the K export amount and rate of canopy leaves and stem nods, and raised their contribution rates to grain yields. The K accumulation were higher in ear leaves (D7, D8) and the leaf beneath (D9). The K accumulation in stem segments gradually increased from top to base of the canopy. The K accumulation in D7, D8, and D9 leaves and stem segments was positively correlated with yield and effective panicle number, and negatively correlated with grain number per ear and 1000-grain weight. And the correlation was closer at silking stage than at maturing stage.

Conclusions The potassium accumulation in the ear and adjacent leaves and stem nodes significantly influence the yield of spring maize. High density will promote the K accumulation, and the export amount and rate of potassium of leaves and stem nodes, as well as their contribution rates to grain yields, and maximize the potential for yield increase.