Abstract
ABSTRACT Nitrogen (N) fertilization has been tested for the mitigation of salt stress in some species including fruit crops. However, special attention should be paid to the source of N, due to the different compositions and saline indices of the fertilizers, particularly when irrigation is conducted using waters with salinity levels that are restrictive to agriculture. Thus, this study evaluated the effect of fertilization with N sources on the growth and gas exchanges of soursop irrigated with saline water after transplanting. The experiment was carried out in greenhouse at the Center of Technology and Natural Resources of the Federal University of Campina Grande, and treatments were arranged in randomized blocks, in 4 x 4 factorial scheme, corresponding to electrical conductivity of water - 0.5, 1.1, 2.5 and 3.5 dS m-1, and the N sources urea, ammonia sulfate, calcium nitrate and potassium nitrate, with three replicates. Growth and gas exchanges of soursop at 110 days after transplanting were not influenced by either the interaction between water salinity and N sources or the individual action of N, but were inhibited by the increase in water salinity from 0.5 dS m-1. Increasing water salinity inhibited stomatal opening and carboxylation in the leaves.
Highlights
This study aimed to evaluate the effect of fertilization with N sources on the growth and gas exchanges of soursop, after transplantation, irrigated with saline water
None of the variables responded to the effects of either the interaction between irrigation water salinity and N sources or the respective N sources individually
This situation is in accordance with Oliveira et al (2010), who observed that the interaction between water salinity and N sources did not interfere significantly with the leaf growth and phytomass accumulation by sunflower (Helianthus annus L.)
Summary
One of the serious problems of water salinity for plants is the loss of photosynthetic activity, attributed to stomatal and non-stomatal limitations (Cha-um & Kirdmanee, 2011; Freire et al, 2014; Sousa et al, 2016), which negatively affect crop growth and yield (Kusvuran, 2012). This situation justifies the conduction of research in an attempt to reduce the deleterious effects of salts on the plants. There are studies about the attenuating action of calcium nitrate and potassium nitrate on the salt stress on the melon crop (Fernandes et al, 2010; Andrade Júnior et al, 2011)
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