Abstract
ABSTRACT Adequate crop fertilization is one of the challenges for agriculture. Measuring gas exchange and biomass accumulation may be used to adjust crop management. The effect of fertigation with potassium (0 kg ha-1, 54 kg ha-1, 108 kg ha-1 and 216 kg ha-1) and nitrogen (0 kg ha-1, 67 kg ha-1, 134 kg ha-1 and 268 kg ha-1) on gas exchange and biomass accumulation in eggplant was assessed under greenhouse conditions. The net photosynthesis, stomatal conductance, transpiration, internal CO2 concentration, instantaneous carboxylation efficiency, water-use efficiency and total dry weight were evaluated. With the exception of K for water-use efficiency and N for internal CO2 concentration, all the other gas exchange parameters were significantly affected by the K and N doses. There was an interaction between N and K doses for net photosynthesis, stomatal conductance, transpiration and instantaneous carboxylation efficiency. The highest values for net photosynthesis, stomatal conductance, transpiration rate, carboxylation instantaneous efficiency and total dry weight were found in the range of 125-185 kg ha-1 of K and 215-268 kg ha-1 of N.
Highlights
Adequate crop fertilization is one of the most important factors for improving yield (Bhuvaneswari et al 2014)
Higher doses of K reduce the net photosynthesis, possibly because of the reduction in the soil osmotic potential, which is not tolerated by the crop (Andrade Junior et al 2011)
Our results indicate a balance among the variables net photosynthesis, stomatal conductance and transpiration rate in eggplant, pointing out that N fertilization and, water-use efficiency, would be a good indicator for other variables
Summary
Adequate crop fertilization is one of the most important factors for improving yield (Bhuvaneswari et al 2014). Nitrogen (N) is an element highly demanded by vegetables and presents a low availability, mainly in tropical soils (Pimentel 1998). N is important for the biosynthesis of amino acids which form proteins. It is necessary for the synthesis of chlorophyll and photosynthesis (Lopes 1998, Bhuvaneswari et al 2014). N is strongly related with net photosynthesis rate and, with carbon absorption and vegetable growth, varying between plant species and functional groups (Felsemburgh 2006). Aminifard et al (2010) observed differences in eggplant leaf chlorophyll content under different N fertilization
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