Nitrogen availability effects on gas exchange measurements in field-grown maize (Zea mays L.) under irrigated Mediterranean conditions

There are limited studies about the effect of nitrogen (N) deficiency on leaf growth, N status, and photosynthetic capacity of maize grown under field conditions in a Mediterranean climate. The objective of this work was to evaluate the effect of different levels of mineral N availability on leaf gas exchange parameters of sprinkler irrigated maize. The experiment was conducted in a conventional maize field located in the central part of the Ebro valley (Spain) during two seasons. Using a portable LICOR-6400 equipment, instantaneous measurements and light response curves to gas exchange were conducted in plots with different levels of N supply ranging from deficient (no fertilized) to over-fertilized (300 kg N/ha). In addition to gas exchange measurements, mineral soil N content, chlorophyll meter readings (CMR), leaf N content, and grain yield were measured in the different plots. Results showed that grain yield reached a plateau (14.5 Mg/ha) when the mineral N available was about 179 kg/ha. CMR were linearly and highly related to total N in ear leaves. The relationship between light-saturated leaf photosynthesis measurements and CMR was significant but very weak (R2=0.13) at V8 and V14 stages but increased later in the growing season (R2=0.52). Plants with intermediate levels of N supply (48<CMR<54) tended to have slightly higher assimilation rates than plants with higher CMR readings. As the available N increased, the saturation point, the light compensation point and significant increases of dark respiration rate were observed. Under the conditions of the study, leaf N contents of 1.9% in the ear leaf were enough to maximize leaf assimilation rates with no need to over-fertilize the maize crop. Additional key words: photosynthesis; dark respiration; nitrogen deficiency; stomatal conductance Abbreviations used: An (net assimilation rate); Ci (intercellular CO2 concentration); CMR (chlorophyll meter reading); gsw (stomatal conductance to water vapour); LCP (light compensation point); LPR (linear plateau response); PAR (photosynthetic active radiation); QE (quantum efficiency); QPR (quadratic plateau response); Rd (dark respiration rate); RMSE (root mean square error); SP (saturation point); Tr (transpiration rate); WUE (water use efficiency). Authors’ contributions: Conceived and designed the experiments: RI. Performed the experiments: RI and MG. Analyzed the data and wrote the paper: RI, MG and MS. Citation: Isla, R.; Guillén, M.; Salmerón, M. (2016). Nitrogen availability effects on gas exchange measurements in field-grown maize (Zea mays L.) under irrigated Mediterranean conditions. Spanish Journal of Agricultural Research, Volume 14, Issue 4, e0806. http://dx.doi.org/10.5424/sjar/2016144-9109. Received: 09 Dec 2015. Accepted: 11 Oct 2016. Copyright © 2016 INIA. This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial (by-nc) Spain 3.0 Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Funding: Spanish Ministry of Science and Innovation (Project AGL2009-12897-C02-02) and FEDER funds. Competing interests: The authors have declared that no competing interests exist. Correspondence should be addressed to Ramón Isla: [email protected]