A study of the pattern of sulphur responses shown by dryland lucerne on some brown-grey earths

Abstract

Field trials showing apparently anomalous lack of response to sulphur topdressing of dryland lucerne on brown-grey earths in the Maniototo basin, Central Otago, were followed up by soil studies.Soil analyses showed the presence of sulphate in the deeper layers (2 to 4 ft) of the non-responsive soils, but no such accumulations were present in the responsive soils.Sulphur concentrations in lucerne from the non-responsive soils were normal (0.19% S or greater), but lucerne from the responsive soils had lower sulphur levels (0.15 to 0.17% S).Conditions leading to the presence of sulphate in the subsoils are discussed and two situations are recognised: (a) the older browngrey earths have accumulations of sulphate-bearing salts in the subsoil, often below the c\aypan; and (b) the lower horizons of the younger brown-grey earths are continually replenished with sulphate which is present in low concentrations in the ground water.The significance of the results in relation to fertiliser recommendations for dryland lucerne on brown-grey earths is discussed.

A lysimeter study of nutrient losses from urine and dung applications on pasture

“…There appears to be little that can be done to recover the K except possibly using deep-rooting plants such as lucerne. Blakemore et al (1969) have shown that lucerne can recover SO; from a considerable depth and possibly this plant could also recover K from deeper soil.…”

Potassium removal from soil by lucerne over three years and the effect of potassium topdressing

“…Lucerne, however, is a deep-rooting plant and there is evidence that it can obtain significant amounts of nutrients from subsoil horizons. Blakemore et al (1969) attributed an apparent lack of response of dryland lucerne to sulphur applications, 011 …”

Sulphur in New Zealand soils

“…The competitive advantage of phosphate over sulphate is implicit in the methods commonly used to extract adsorbed sulphate from soils. Salts and dilute acids of weakly (non-specifically) adsorbed anions, such as Cl and N03-, extract essentially only water-soluble S04 2 -(e.g., White 1959;Williams & Steinbergs 1959;Chao 1964;Roberts & Koehler 1968;.Blakemore et al 1969;Carson et al 1972;Tabatabai & Bremner 1972a;Westerman 1974;Saunders & Cooper 1975). To remove adsorbed sulphate from strongly anion-retentive soils, phosphates, or other specifically adsorbed anions (e.g., hydroxyl, fluoride), are required (e.g., Ensminger 1954;Fox et al 1964;Barrow 1967a;Blakemore et al 1968: Bromfield 1972 .…”

“…The legume Lotus pedunculatus grew well despite a low content of adsorbed sulphate in the topsoil, probably because of its ability to tap the much greater reserves of sulphate in the subsoil. In an extreme example, Blakemore et al (1969) demonstrated the ability of dryland lucerne to obtain soluble S04 from depths of 100 em or more in some brown-grey earths of Central Otago, whereas the upper soil horizons were extremely S deficient.…”

“…Thus, White (1959) employed very dilute (0.001 M) HCl as an extractant for available sulphate-S in some S-deficient South Island soils which contained predominantly soluble sulphate-So Likewise Blakemore et al (1969) used a 0.15% CaCh solution (Williams & Steinbergs 1959) to extract soluble sulphate from deep profiles of dryland soils in Central Otago. since very little additional S was extracted by a phosphate reagent.…”