Salinity and specific ion effects on onion establishment in relation to disposal of desalting concentrates

Abstract

A B S T R AC TConcentrate from nanofi ltration (NF) is usually enriched with divalent ions, and low in proportions of monovalent ions. Therefore, its disposal to irrigation water may not be deleterious, especially for growing crops susceptible to specifi c effects of Na and/or Cl. This possibility was examined in a greenhouse by observing effects of four levels of salinity and ion composition of irrigation solutions on seedling emergence and growth of onions (sensitive to Cl ions) in loamy sand and silt loam. Seedling emergence from surface-irrigated loamy sand was excellent, regardless of the saline solutions used. In subirrigated silt loam, however, seedling emergence was reduced by increasing initial soil salinity and salinity of irrigation solutions, but not by the ion composition. Seedling growth was reduced by increasing Cl to SO 4 ratio only when the Cl concentration of irrigation solutions exceeded a concentration between 10 and 20 me L -1 . The Cl effect seems to appear after seedling growth is fi rst reduced by salinity. The addition of Ca and SO 4 to the irrigation solution reduced seedling growth. The disposal of NF concentrates into irrigation water, and associated impacts on establishment of crops sensitive to osmotic stress should be evaluated mainly by considering an increase in salinity, soil types, and cultural practices.

Salinity and Soil Type Effects on Emergence and Growth of Pepper Seedlings

“…1. This result is consistent with observations by Miyamoto et al (2010) whereby it was reported that salts can accumulate in the surfaces of poorly drained soils as a result of evaporation of saline water, which moves to the surface through capillary action. In the current study, salt accumulation in the surfaces of the silt loam soil was less dramatic.…”

“…Overhead irrigation such as with a sprinkler may help seedling establishment resulting from lower soil salinity at top soil layer, which is evidenced in this experiment. Miyamoto et al (2010) reported that onion seedling emergence and growth were enhanced by overhead irrigation compared with subirrigation in loamy land. Therefore, irrigation with an overhead sprinkler, leaching salts, or increasing seeding density may be options to improve seedling establishment in salt-affected fields and with low-quality irrigation water.…”

“…In another separate salt tolerance study with 20 chile peppers, 'NuMex Joe E. Parker', 'NuMex Nematador', and 'NuMex Primavera' seedlings had significant growth reduction, low survival rate, and severe foliar salt damage when grown in loamy sand and irrigated with nutrient or saline solution at EC of 6.35 dSÁm -1 through the medium surface (Niu et al, 2010;unpublished data). Sanogo (2004) also reported that 'NuMex Joe E. Parker' plants exhibited salt damage at EC of as low as 2.7 dSÁm -1 .…”

“…1). Two soils were used: 1) Blue Point loamy sand, which is characterized as structureless, loose when dry, rapidly drained, moderately alkaline, and calcareous; and 2) Harkey silt loam, which is calcareous and sandier than most alluvial soils of the Rio Grande Valley (Miyamoto et al, 2010). Blue Point loamy sand, similar to Vinton loamy sand, was collected from the south side of the El Paso Research Center property.…”

“…Soil salinity at or near the soil surface increases exponentially with time when saline water is used for irrigation (USDA Staff, 1954). Miyamoto et al (2010) reported that seed germination, seedling emergence, and seedling growth of onions were affected by soil property, salinity of irrigation water, and irrigation method. The dynamics of salt movements and distribution in various soils are poorly understood.…”