Field Crop 2025, Vol.8, No.6, 284-292 http://cropscipublisher.com/index.php/fc 288 However, on the other hand, delayed sowing is not completely without remedial methods. For instance, by appropriately adjusting the planting density, the population structure and the accumulation of assimilation products can still be stabilized to a certain extent (Ji et al., 2024). 5.2 Interactive effects on population structure and yield components Population structure and yield, which may sound like two separate systems, are actually tightly bound together under the combined effect of sowing time and density. Early sowing combined with high density is a typical "yield-increasing combination", which is particularly beneficial for the number of ears and grain filling. However, if the sowing is late and a high density is added, there will be many more troubles: the tillering utilization rate will be low, the number of spikelets will decline, and the seed setting rate will also be held back (Zheng et al., 2020). Of course, it is not to say that high density is completely useless under late sowing conditions. Some experiments have found that it can "replenish some yield", but when replenishment reaches a certain extent, the upper limit is reached. Continuing to increase density may have the opposite effect - lodging, diseases, and grain filling obstacles may all emerge. Overall, the best results often occur in stable combinations such as "early sowing + medium density", which not only ensures the number of ears but also guarantees that the grains can be irrigated. 5.3 Resource use efficiency under representative combinations Not all sowing date density combinations can achieve both high yield and high efficiency. The truly outstanding resource utilization efficiency is often achieved when early sowing is combined with medium to high density - more light is used, water and nitrogen are not wasted, and the entire system operates more smoothly (Santiago-Arenas et al., 2022; Zhu, 2025). Some experiments simply compared the two sowing periods directly. The results showed that even if the nitrogen fertilizer was reduced a little, as long as the sowing was early and the density was properly controlled, the yield still increased and the grouting was more ideal (Zhou et al., 2023; Zhu et al., 2023). In contrast, the combination of late broadcasting and high density not only leads to an uneven distribution of resources but also amplifies the competitive pressure, thereby significantly lowering efficiency. 6 Case Study Analysis 6.1 Development of mechanized direct-seeded rice in South China In South China, when it comes to how to grow rice more conveniently, many people first think of mechanical direct seeding. With the shortage of manpower and the annual increase in costs, coupled with everyone's focus on the "green and efficient" aspect, mechanical direct-seeded rice (DSR) has naturally been widely adopted. Especially for early-maturing indica rice, after the application of precise hole sowing and mechanical row sowing, both the yield and the ability to resist lodging have reached a new level. New techniques like furrow fertilization are also quite practical. The emergence rate, aboveground biomass and harvest index have all improved. Moreover, compared with full-layer fertilization or surface fertilization, the risk of lodging is much lower (Chen et al., 2021). However, it doesn't mean that direct seeding is fine. For instance, in this humid subtropical climate, when there is a lot of rain, direct seeding is very likely to cause soil erosion and phosphorus loss. Overall, the double-cropping rice system has made some optimizations in terms of sowing rate and nitrogen fertilizer management, which can indeed stabilize the yield and enhance the resistance to lodging. 6.2 Field experiment on direct-seeded rice in Shaoguan, Guangdong A field test was also conducted in Shaoguan, and the location selected was quite representative - subtropical and hilly terrain. The study compared three mechanical direct seeding methods, namely dry seeding, water seeding and wet seeding, and used early-maturing indica rice. Over the past two years, it has been found that the yield of dry sowing has always been higher than that of water sowing, with an increase ranging from 6.6% to 26.3%. This advantage mainly stems from an increase in the number of panicles and better emergence. More importantly, plants sown under drought conditions grow strong, have more dry matter, grow faster, and have thick and solid stems. Even small details like short internodes at the base directly affect the lodging performance, and the lodging index naturally decreases. The research conclusion is clear: To carry out mechanical direct seeding in South China, if the sowing method is selected correctly and combined with suitable varieties, both yield and lodging resistance can be achieved simultaneously (Wang et al., 2021).
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