Effects of lime and 5 years' sulphur and phosphorus applications on soil pH, sulphur, and phosphorus status of tussock grassland soils on East Otago uplands

Abstract

The effects of lime and fertiliser application on changes in soil chemical properties of four sites on upland and high country yellow-brown earths and one site on podzolised yellow-brown earth on the Otago Uplands between 470 and 1100 m altitude are reported for a 5-year period. Soil pH was very significantly (P < 0.001) raised 0.6–0.8 units by 4.01 lime/ha and after 5 years, limed soils were 0.3–0.8 pH units above unlimed controls (P < 0.001). Differences were attributed to increasing leaching with increasing rainfall and altitude. Soil SO₄-S levels were increased at all sites by annual application of 50 kg sulphur (S)/ha as gypsum. The decreasing amount of SO₄-S retained within the profile, and the decreasing proportion of total S as SO₄-S with increasing altitude was also related to the increasing leaching. Olsen phosphorus (P) levels in soils were raised quantitatively and significantly in proportion to the amounts applied over 5 years: each 10 kg P/ha applied annually resulted in an average increase of 1 Olsen P unit. Increases were largely confined to the top 100 mm of the profile. Most applied P accumulated in inorganic forms associated with iron (Fe) and aluminium (Al), and there was no significant increase in organic P in the 5 years. It was, however, not possible to account for all applied P. These results are discussed in relation to the improvement of models for predicting appropriate fertiliser recommendations for these soils.

Keywords:

• fertiliser
• lime
• sulphur
• phosphorus
• tussock grasslands
• high country
• soil sulphur
• soil phosphorus
• pH
• soil