Development of ultra-high-yield technology for a wheat-maize double cropping system achieving a 2-ton annual grain yield per mu in the coastal plain of Northern Shandong peninsula, China

The development of ultra-high-yield technology for a wheat-maize double cropping system targeting an annual grain yield of 2 tons per mu in the coastal plain of northern Shandong Peninsula represents a significant agricultural initiative led by the Crop Chemical Control Center of China Agricultural University and Laizhou Jinhai Seed Industry in Laizhou, Shandong province. Through the careful selection of superior varieties, optimized planting densities, and integrated water and fertilizer management, high grain yields and efficient cultivation of both wheat and maize have been achieved. In the 2023 growing season, the combined yield of wheat and maize reached 31,323.90 kg hm^-2 (2,088.26 kg mu^-1). Notably, the winter wheat crop—evaluated by experts organized by the Ministry of Agriculture and Rural Affairs—set a new regional yield record for the Huang-Huai-Hai Plain, with an actual yield of 13,213.35 kg hm^-2 (880.89 kg mu^-1). The variety Yannong 1212 exhibited a spike density of 692.0 spikes m^-2, an average of 40.1 grains per spike, a thousand-grain weight of 52.55 g, single-plant yield of 4.74 g, harvest index of 0.56, and water use efficiency (WUE) of 3.24 kg m^-3. For summer maize, the variety Zhongjinyu 2513 achieved a spike density of 9.1 spikes m^-2, an average of 584.7 grains per spike, a thousand-grain weight of 379.31 g, single-plant yield of 206.25 g, harvest index of 0.58, and WUE of 2.86 kg m^-3, with an actual yield of 18,110.55 kg hm^-2 (1,207.37 kg mu^-1). In a 2024 repeated trial, the total yield remained high at 30,997.00 kg hm^-2 (2065.13 kg mu^-1). This study summarizes the key management practices and main agronomic indicators contributing to high-yield wheat-maize double cropping in northern Shandong, offering a valuable reference for similar production systems in the region.