Spraying Ethephon Effectively Increased Canopy Light Transmittance of Densely Planted Summer Maize, Thus Achieving Synergistic Improvement in Stalk Lodging Resistance and Grain Yield.

Increasing planting density is an effective way to improve maize yield, but high plant populations often cause a lodging problem. This experiment was conducted to investigate the effect of increasing planting density on stalk lodging resistance and grain yield, and to explore the effects on stalk and yield properties of spraying ethephon in densely planted summer maize. The summer maize hybrid, Xundan20 (XD20), was used as experimental material. It was grown by spraying water (CK) or ethephon (E) at BBCH (BASF, Bayer, Ciba-Geigy and Hoechst) 17 under three different planting densities of 60,000 plants ha-1 (L), 75,000 plants ha-1 (M) and 90,000 plants ha-1 (H) in order to explore the possibility of synergistic improvement in stalk lodging resistance and grain yield. The results from this experiment suggested that the gravity center height of densely planted summer maize was significantly increased, the stem diameter, area and number of vascular bundles were significantly decreased and the dry weight per unit internode was significantly decreased, thereby weakening the stalk rind penetration strength and bending performance, resulting in a significant increase in lodging percentage. The ear height was significantly decreased and the SPAD (soil and plant analysis development) and canopy light transmittance were increased after spraying ethephon; then, the internode dry weight per unit length was increased and the stalk rind penetration strength and bending performance were enhanced so as to significantly reduce the lodging percentage and increase the grain yield. The correlation analysis further showed that lodging percentage was significantly negatively correlated with stem diameter, area and number of vascular bundles and stalk bending performance, but there were no strong relationships with grain yield. This suggested that the synergistic improvement in stalk lodging resistance and grain yield was not contradictory. Under the experiment conditions, the effect of spraying ethephon was most significant when the planting density was 90,000 plants ha-1. At the time, the lodging percentage and grain yield were 12.2% and 11,137.5 kg ha-1, which were decreased by 44.6% and increased by 8.0% compared with the control treatment. Scientific chemical regulation could significantly improve the stalk lodging resistance and grain yield of densely planted summer maize.

The Allocation of Water Resources in the Midstream of Heihe River for the "97 Water Diversion Scheme" and the "Three Red Lines".

Rapid economic and societal development increases resource consumption. Understanding how to balance the discrepancy between economic and social water use and ecological water use is an urgent problem to be solved, especially in arid areas. The Heihe River is the second-largest inland river in China, and this problem is notable. To ensure the downstream ecological water use, the "Water Distribution Plan for the Mainstream of the Heihe River" (97 Water Diversion Scheme) controls the discharge of Yingluo Gorge and Zhengyi Gorge, while the "Opinions of applying the strictest water resources control system" (Three Red Lines) restricts the water use. With the development of the economy and agriculture in the midstream, Zhengyi Gorge's discharge cannot reach the Heihe River's ecological water downstream. This paper is under the constraints of the "97 Water Diversion Scheme" of Heihe River and the "Three Red Lines" of the total water use control index for Zhangye County. We constructed a water resource allocation model for the midstream of Heihe River to reasonably allocate water resources in the Heihe River's midstream and downstream. This model is divided into three parts: Establish the mathematical equation, simulate the water consumption under the different inflow conditions, and ensure each water user's demand. The result showed that if we fail to confine total water consumption in the midstream, through the reasonable allocation of water resources, the real water use and water consumption of the middle Heihe River will be greater than the "97 Water Diversion Scheme" and the "Three Red Lines." If we confine water consumption, they will be within the "97 Water Diversion Scheme" and the "Three Red Lines," at the same time, they can reach the downstream of the Heihe River's ecological water. Besides, under the premise of satisfying the economic water and ecological water downstream of the Heihe River, returning farmland to wasteland and strengthening water-saving measures will improve water efficiency and be more conducive to allocating water resources.