Effects of salinity, growth condition, and soil type on shoot dry matter of Alfalfa (Medicago sativa) – a meta-analysis

ABSTRACT

Salinity is a spatially complex and dynamic property of soil that adversely impacts plant metabolism and rhizobium capacity for symbiotic nitrogen fixation, thus affecting alfalfa (Medicago sativa) growth. The objective of present study was to conduct the first meta-analysis to understand the influence of soil salinity, experimental growth condition, and soil type on alfalfa shoot dry matter. Thus, random-effects model meta-analysis was performed using Comprehensive Meta-Analysis (CMA) version 3 software across 10 published articles generating 68 observations. The effect sizes were determined as the natural logarithm of the response ratio as a metric response of alfalfa shoot dry matter under saline treatments versus the control treatment. Three moderators used in the study were: 1) Salinity, categorized as (low, 0–5 dS/m; medium, 6–15 dS/m; and high, 16–30 dS/m); 2) experimental conditions (field experiment, greenhouse, growth chamber); and 3) soil type (sand, sandy loam). Alfalfa shoot dry matter decreased significantly under medium and high salinity levels (p≤ 0.05); whereas low salinity did not have significant effect on shoot dry matter (p≥ 0.05). The decrease in shoot dry matter was 40, 43, and 50% under field, greenhouse, and growth chamber, respectively. In terms of soil type, sandy loam soil reduced the alfalfa shoot dry matter by 40%, whereas sandy soil showed a 59% decrease. Low saline soils (i.e., <5 dS/m) and/or sandy loam soil type under field conditions can increase alfalfa shoot dry matter and can outperform high saline soils (i.e., between 6 and 30 dS/m) and/or sandy soil under growth chamber conditions.

KEYWORDS:

• Alfalfa
• shoot dry matter
• salinity stress
• growth condition
• soil type
• meta-analysis

Acknowledgments

Authors thank Dr. Robert M. Augé and Heather D. Toler from the University of Tennessee, Knoxville for technical support.