Growth and nitrogen (N₂) fixation response of arrowleaf clover to mineral nitrogen and 2(N‐morpholino)‐ethanesulfonic acid at low pH

Abstract

Evaluation of legume response to acidic conditions can be difficult when using nutrient solutions because of fluctuations in solution pH. The organic buffer 2(N‐morpholino)‐ethanesulfonic acid (MES) has been used for stabilizing pH in nutrient solution studies. We evaluated the effectiveness of MES (5.0 mM) to stabilize solution culture at pH 5.5 with and without mineral N (0 or 1.0 mM NH₄NO₃) and its influence on growth and N₂ fixation of arrowleaf clover (Trifolium vesiculosum Savi). The buffer maintained pH stability ± 0.1 pH units in the presence or absence of mineral N. In the absence of mineral N, the quantity of N₂ fixed by plants grown with MES was not significantly different from that fixed by plants grown without MES. However, with mineral N, N₂ fixation was reduced 37% with addition of MES. Tissue analysis indicated a small increase in Ca and Mg concentration for plants grown with MES. Caution should be exercised in the use of MES in studies of N₂‐fixing legumes when mineral N is included.

Notes

Contribution of the Texas Agricultural Experiment Station, College Station, TX. This study was supported by Hatch Project 6997.

Soil and Crop Sciences Department, Texas A&M University, College Station, TX 77843