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 氮肥施用已被用于缓解包括果树作物在内的部分物种的盐胁迫。然而，由于不同肥料的组成与盐渍指数存在差异，需特别关注氮源类型，尤其当使用对农业生产具有限制性的盐度水源进行灌溉时。为此，本研究评估了不同氮源施肥对移栽后灌溉咸水的刺果番荔枝（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（Federal University of Campina Grande）技术与自然资源中心的温室中开展，试验采用4×4因子设计的随机区组方案，设置4个水盐电导率梯度（0.5、1.1、2.5、3.5 dS m⁻¹）与4种氮源：尿素、硫酸铵、硝酸钙、硝酸钾，共设置3次重复。移栽后110天的刺果番荔枝生长与气体交换参数，既未受水盐度与氮源的交互作用影响，也未受氮源单独作用的影响，但会随水盐度从0.5 dS m⁻¹升高而受到抑制。水盐度升高会抑制叶片的气孔开放与羧化作用。