Growth and gas exchanges in soursop under irrigation with saline water and nitrogen sources

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.

摘要 氮肥（N）配施已被证实可缓解部分物种（包括果树作物）遭受的盐胁迫。然而，由于不同肥料的成分与盐渍化指数存在差异，需特别关注氮肥的来源，尤其当采用农业生产受限的咸水进行灌溉时。为此，本研究评估了不同氮肥源对移栽后咸水灌溉下刺果番荔枝（soursop）生长与气体交换参数的影响。
本试验于坎皮纳格兰德联邦大学技术与自然资源中心的温室中开展，采用4×4因子试验设计的随机区组排列，设置4个灌溉水电导率梯度：0.5、1.1、2.5与3.5 dS·m⁻¹，以及4种氮肥源：尿素、硫酸铵、硝酸钙与硝酸钾，每个处理设置3次重复。
移栽后110天的刺果番荔枝生长与气体交换参数，未受水盐与氮肥源的交互作用及氮肥单因子作用的影响，但随灌溉水电导率从0.5 dS·m⁻¹升高而受到抑制。灌溉水盐度升高会抑制叶片气孔开放与羧化作用。