Oats: fertilisers and plant nutrition

Page last updated: Tuesday, 22 May 2018 - 12:02pm

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Oats can be found to be highly susceptible to Mn deficiency which can cause significant yield losses. In severe cases, the crop may die entirely.

Tissue tests and visual symptoms can be sued to help diagnose Mn deficiency. Mn concentrations less than 20ppm (mg/kg) in whole shoots indicate Mn deficiency. The concentrations of Mn in tissues vary for different oat varieties.

Applying manganese sulphate (25% Mn) as a foliar spray at a rate of 4kg/ha (1kg Mn/ha in 50-100 L of water) immediately symptoms appear is usually effective in correcting a Mn deficiency,, however, a repeat spray a few weeks later may be necessary.

The application of ammonium sulphate and ammonium nitrate can markedly reduce Mn deficiency symptoms. Drilling fertilisers enriched with Mn can reduce the risk of crop damage from Mn deficiency. However, even where an ammonium enriched fertiliser has been used severely deficient patches may still require a foliar Mn spray.

Mn deficiency symptoms

In oats, Mn deficiency produces a condition called 'grey speck' with occurs in patches. Oats become pale green and young leaves have spots or lesions of grey/brown necrotic tissue with orange margins. These lesions will coalesce under severe Mn deficient conditions. Plants are weak, stunted, floppy and pale green-yellow and appear water-stressed even when adequate soil moisture is available.

Close examination of the leaf may show slight interveinal chlorosis. The distinction between green veins and yellow interveinal areas is poor. Symptoms can be confused with red leather leaf, which is favoured by prevailing high humidity in high rainfall areas. Symptoms can also be mistaken for take-all.

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