Abstract
Phosphorus (P) is an important macronutrient required for crop growth but a finite resource in agriculture. The objective of this study was to examine the effects of soybean seed size and seed P content on growth and P accumulation up to anthesis (30–40 DAP). Pot experiments were carried out in a greenhouse with 15 soybean genotypes of different seed size (TKW 146–304 g) and with two substrates differing in plant available P, i.e., low P (LP) at 6.17 mg kg−1 vs. high P (HP) at 68.12 mg kg−1 CAL-P. The observations included measurements of seed and shoot dry matter and P concentrations as well as root characteristics. In the case of LP, shoot P accumulation relied, to a large degree, on seed P reserves during the vegetative growth period. In the case of HP, however, the role of seed P is negligible with regard to absolute P uptake. Yet, a very close linear relationship between seed P and shoot P uptake was also confirmed at HP. Some genotypes reacted more positively than others on HP in biomass production and P uptake, but none of the selected genotypes showed an outstanding biomass production or P uptake under LP. Total root length or root surface area of soybean did not explain differences in P uptake between genotypes at either P supply level. Overall, no substantial genotypic differences were observed in P use efficiency under P deficiency apart from the effect of seed P reserves. We conclude that seed size can be considered an important trait when screening genotypes for fast early P accumulation and growth.
Highlights
Soybean belongs to the five arable crops with the largest production area worldwide
In the case of high P (HP), the role of seed P is negligible with regard to absolute P uptake
No substantial genotypic differences were observed in P use efficiency under P deficiency apart from the effect of seed P reserves
Summary
Soybean belongs to the five arable crops with the largest production area worldwide. It was cultivated in 2019 on 121 M ha in the world and on 908,000 ha in the European Union. Studies of [5,6,7] suggest that seed P maintains the growth of young soybean plants beyond the seedling stage, especially under low P phytoavailability from soil. It may enhance the shoot P uptake through earlier access to the soil P resources by a faster root establishment. [8] assumed that heavier seeds with higher seed P content could be considered as an adaptation trait developed by plants in response to low soil P phytoavailability This hypothesis is confirmed by recent findings indicating genetic associations between soybean seed size and P efficiency in low-P environments [9,10]. In contrast to higher P reserves present in larger seeds, correlations between soybean seed size and other characters such as grain yield, seed protein, or seed carbohydrate content are generally not consistent but depend on the genetic population investigated, as well as on specific environmental conditions
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