Source-sink relationship of soybean accessed by increasing in solar radiation through the plant canopy

Abstract

The photosynthetic metabolism is a key point to improve soybean yield. In this work, we demonstrated that radiation use by soybean plants can be improved, aiming to improve the grain yield in the lower canopy. The objective of this study was to observe whether the increase in solar radiation input in the canopy of soybean plants improves their yield performance. Three experiments were carried out during the 2017/2018 season. For each experiment, treatments consisted in the opening of one or two side rows of cultivation at the R2 and R5 stage of soybean plants (NA5909RR) until maturity, plus a control. Increase on solar radiation provided by the oppening of rows enhanced the yield potential in the nodes of the lower canopy, mainly when two rows were opened. The main benefits of increasing the radiation available throughout the canopy of soybean plants are observed in the number of pods and thousand-grain weight, demonstrating the importance of increasing the availability of assimilates in lower leaves. Interestingly, the benefits of the increase in solar interceptation were observed regardless of the yield potential of the area, which varied between 4.9 and 6.7 ton ha -1 .

Potencial fisiológico de sementes de diferentes estratos da planta de soja em densidades reduzidas

“…The factors that may have led to low seed germination in the lower stratum of the plants may have been; microclimate that was more favorable to the development of phytopathogenic microorganisms in the seeds, low penetration of agrochemicals in the lower parts of the canopy (Holtz et al, 2014), and low source strength of the leaves of the lower nodes. The seeds inserted in the lower nodes were adjacent to the leaves that have reduced light interception; which led to the decreased transport of photosynthates to the legumes, as transport occurs owing to the proximity between source and sink (Fioreze et al, 2022) Furthermore, in cultivars with indeterminate growth, the seeds positioned in the lower stratum of the plants had a more advanced development than those above them. This signifies that the former group completed the period of seed formation/ filling earlier, whereas soybeans maintained many leaves and were not ready for harvest (Thomas, 2018).…”