Soil-based cycling and differential uptake of amino acids by three species of strawberry (Fragaria spp.) plants

Evidence is growing that amino acids can be an important source of plant N in nutrient limited natural ecosystems, but relatively little is known about the effect of agricultural management on soil amino acid pools and turnover. Organic management in particular relies on slow-release organic inputs as fertilizer, which could result in greater pools of soil amino acids available for plant uptake. Moreover, we know little about potential differences in amino acid uptake ability within plant families and whether this ability may have been lost during domestication. In order to determine the relative effects of soil type and management on amino acid turnover, we measured the effect of fine- versus coarse-textured soil and organic versus conventional management on free amino acids and proteolytic activity in the field. Secondly, we conducted greenhouse experiments to determine the ability of domestic and wild strawberry to utilize amino acid-N. Fine-textured and organically managed soils contained significantly higher total C and N than coarse-textured and conventionally managed soils. There were no significant differences in free amino acids or protease activity in relation to texture or management. Amino acid turnover was calculated at 0.7-1.5 h. Turnover time was significantly greater in fine-textured soils. Turnover time as a result of substrate additions was significantly shorter in coarse-textured soils; in fine-texturedsoils turnover time was shorter under conventional management. This suggests less competition for amino acids in soils with greater C, N and/or cation exchange capacity (CEC), such as fine-textured and organically managed soils. Two wild species of strawberry, Fragaria virginiana and Fragaria chiloensis, took up significantly more 14C labeled glycine than the domesticated species, Fragaria fragaria. More research is needed to determine whether strawberry cultivars could be selected or bred for their ability to capture amino acid-N, thus improving N-use efficiency in farming systems relying on the breakdown of organic matter as a N source.