Comparative responses to inorganic and organic fertilization of chile pepper plants grown under saline conditions

Three soil salinity levels were used to evaluate the effect of two nitrogen sources on plant growth and fruit yield, ion uptake and transport, nitrogen and water use and fertilizer efficiencies, and salt tolerance of chile pepper plants (Capsicum annuum L.) cv. Sandia grown under greenhouse conditions for two years. Treatments consisted of two organic N rates (120 and 200 kg ha-1) and an inorganic N rate (120 kg ha-1) in 2001 and the two rates of both N sources in 2004 combined with low, moderate and high (1.5, 4.5 and 6.5 dS m -1) salinity levels arranged in randomized complete block designs with four replications. Salinity decreased plant growth and fruit yield. Nitrogen sources induced notable differences in both parameters. While relative growth rate was greater in plants fertilized with the inorganic fertilizer, the greatest fruit yields were produced with the organic fertilizer. Salinity decreased Ca and Mg uptake in roots but increased them in shoots. While root Na and K uptakes were not affected by salinity, their uptake increased in the shoots as salinity increased. A similar behavior to root cation uptake was observed in fruit cation uptake. An antagonistic effect was observed between plant Cl uptake and plant N uptake. While plant Cl uptake increased as salinity increased, N uptake decreased. As a result of this decreased N uptake, nitrogen use efficiency also decreased as salinity increased. Water use efficiency decreased as salinity increased in 2001, but was not affected in 2004. Chile pepper plants fertilized with the organic source were more salt tolerant than plants fertilized with the inorganic source in 2001. However, plants fertilized with 120 kg ha-1 inorganic source were more salt tolerant than those fertilized with the same N rate of organic fertilizer in 2004. Opposite results were noted with plants fertilized with high N rates.; Water use increased approximately 55% in chile pepper plants when mean air temperatures inside the greenhouse were higher during the 2004 experiment compared to 2001 experiment. On the contrary, all parameters values evaluated in 2004 were lower than the same parameters evaluated in the 2001 experiment.