Zinc deficiency on the shallow Soil of Niue i. field investigations

Abstract

A preliminary survey of taro crops on Niue in April 1964 showed that poor crop growth was associated with shallow soils of high pH containing considerable quantities of calcium carbonate.Using Crotalaria anagryoides (a leguminous plant grown for green manure) as an indicator plant, it was found that zinc deficiency was a major cause of poor growth on shallow calcareous soils.It is concluded that cultivation of shallow soils aggravates the problem of zinc deficiency, by enrichment of the topsoil with underlying coral sand and limestone, thereby raising the pH.

Mineralisation of nitrogen and metabolism of ammonium sulphate in some soils of Niue Island

“…Ammonium fertilisers were not recommended for use on the alkaline soils of the Cook Islands because of possible volatilisation losses, but no experimental data were recorded (Grange and Fox 1953). Several reports, such as those of Allison (1955) and Gasser (1964), have shown that volatilisation losses are less when fertilisers are applied at depth in a soil than when broadcast on the surface, and Widdowson (1965) has recommended that ammonium sulphate be mixed with the soil or banded several inches deep in the row before planting crops in Niue. Under thes~ conditions of placement the NH4 + -N could be adsorbed more efficiently on exchange sites in the soil and either nitrified or taken up by plants before appreciable volatilisation occurred.…”

“…Niue is a small tropical island in the Pacific Ocean (latitude 19 deg S) with an area of about 65,000 acres. Its soils are classified as latosols of high base status and have been described by van Westendorp (1964), Widdowson (1965), and Wright and van Westendorp (1965).…”