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Newcastle upon Tyne University (2002)

Sulphur nutrition and wheat production in northern Iran

Shahsavani, S.

Titre : Sulphur nutrition and wheat production in northern Iran

Auteur : Shahsavani, S.

Université de soutenance : Newcastle upon Tyne University

Grade : Doctor of Philosophy (PhD) 2002

Field surveys were undertaken in two Provinces of northern Iran, Golestan, a sub-humid region with high temperature and moisture, Khorasan, recognised as a semi-arid region. In Golestan 75% of surveyed sites were at risk of S deficiency, compared to 50% in Khorasan. Different procedures have been compared for their effectiveness in measuring soil SO4-S levels and as an indicator of S deficiency.From a pot experiment it was established that the surface 30 cm of soils obtained from irrigated and rainfed fields in both Provinces contained less SO42- than soils from the 30 to 60 cm horizon. Application of 20 and 40 kg S ha-1 as gypsum resulted in a significant increase in wheat yields and S uptake.Field experiments were established in two growing seasons under irrigated and rainfed conditions in both Provinces. Significance yield response to S was obtained at S deficient sites in both Provinces. Leaf S concentration was greater at S sufficient site compared to S deficient sites. Application of S fertilizer to these S-deficient sites resulted in a significant increase in leaf S concentration in both growing seasons.Soil extractable SO4-S increased with increasing the level of S application in both seasons. The increase in soil SO4-S concentration was greater in the 30-60 cm horizon of soil than the 30 cm horizon. Soil microbial biomass-S increased with irrigation and in those treatments receiving 40 k S ha-1. Sulphase adsorption decreased and desorption increased with increasing S application. The decrease in adsorption was more pronounced in irrigated fields than rainfed fields.A sulphur balance is proposed to assess the risk of S-deficiency in wheat under Iranian conditions. The balance predicts S deficiency on the basis of atmospheric S deposition, irrigation, crop S uptake and leaching. The balance can be used to identify areas with a high-risk of S defiency in northern Iran.

Mots clés : Agricultural chemistry, fertilisers, animal feed, silage, pesticides, soil conditioners ; 02D - Agronomy, crop production, crop diseases, horticulture

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