Yield, growth and grain nitrogen response to elevated CO2 in six lentil (Lens culinaris) cultivars grown under Free Air CO2 Enrichment (FACE) in a semi-arid environment

Abstract

Yield, growth and grain nitrogen response to elevated CO2 in six lentil (Lens culinaris) cultivars grown under Free Air CO2 Enrichment (FACE) in a semi-arid environment." European

Water availability moderates N2 fixation benefit from elevated [CO2]: A 2‐year free‐air CO2 enrichment study on lentil (Lens culinaris MEDIK.) in a water limited agroecosystem

“…Consistent with previous results on wheat from the same site (Houshmandfar et al, ; Tausz‐Posch, Seneweera, Norton, Fitzgerald, & Tausz, ), e[CO 2 ] stimulated net assimilation rates (A sat ) and biomass of lentil in our study (by 25% and 30%). Stimulation of grain yield by e[CO 2 ] was increased more in the high rainfall season (63%) than in the dry season (18%), in line with previous results on wheat and lentil in the same experimental facility (Bourgault et al, ; Fitzgerald et al, ; Houshmandfar et al, ; O'Leary et al, ), but in contrast to a long‐held paradigm that the CO 2 fertilization effect is greater under drier than wetter conditions (Kimball, ; Leakey, Bishop, & Ainsworth, ; McGrath & Lobell, ). That paradigm was challenged by a recent meta‐analysis (van der Kooi et al, ) and also by long‐term results from a FACE site in a high rainfall agroecosystem, demonstrating that severe drought diminished yield stimulation by e[CO 2 ] to zero (Gray et al, ).…”

“…In legumes, the known decrease in grain [N] under e[CO 2 ] is less prevalent than in non‐legume crops (Myers et al, ), and we found that e[CO 2 ] decreased grain [N] by 4%, but only in the dry season. Decreases in grain [N] under e[CO 2 ] in a low rainfall environment were previously observed in lentil and field pea (Bourgault et al, ; Bourgault et al, ). In the high rainfall season, stimulation of N 2 fixation by e[CO 2 ] was apparently sufficient to maintain grain [N] with higher yield, similar to reports in soybean in high rainfall agroecosystems (Gray et al, ) and supported by the positive correlation between grain [N] and N deposition to grain from fixation (Figure ).…”

“…PBA Ace is a high yielding, vigorous, and medium‐seeded commercial cultivar, which is well suited to dry areas. The breeding line HS3010 has a smaller harvest index and displays greater biomass accumulation under favourable environments (Bourgault et al, ).…”

“…Water availability can also determine the ability of legumes to maintain grain [N] by moderating N 2 fixation. For example, in high rainfall conditions, soybeans maintained grain [N] under e[CO 2 ] (Gray et al, ), but experiments in semi‐arid environments showed small but significant decreases in grain protein concentration of lentil (Bourgault et al, ), field pea (Bourgault, Brand, Tausz, & Fitzgerald, ), and chickpea (Lam, Chen, Norton, & Armstrong, ). Such interactions with environmental conditions highlight the importance of assessing and better understanding N 2 fixation under e[CO 2 ] in water limited agroecosystems.…”

“…For legumes, intraspecific variability in grain yield response to e[CO 2 ] has been reported for soybean (Bishop, Betzelberger, Long, & Ainsworth, ), common bean (Bunce, ), and cowpea (Ahmed, Hall, & Madore, ) where increased grain yield under e[CO 2 ] was associated with greater harvest index, short stature, and greater number of pods. However, no clear cultivar difference in response to e[CO 2 ] of grain yield was observed for six lentil genotypes grown under higher [CO 2 ] in a semi‐arid environment (Bourgault et al, ). Apart from growth and yield response, differences in N 2 fixation ability in response to e[CO 2 ] would be a useful candidate trait for selecting genotypes for a carbon‐rich environment.…”