Manganese (Mn) is often underestimated in plant nutrition. Its availability to plants is influenced by several factors, which can lead to Mn deficiency or toxicity. The objective was to evaluate the transformation of soil Mn over 21 years in a long-term field experiment. Fertilising with (i) sewage sludge 1 (SS1); (ii) sewage sludge 3(3 times higher nitrogen (N) dose, SS3); (iii) farmyard manure (FYM); (iv) mineral nitrogen, phosphorus and potassium (NPK) and (v) mineral nitrogen in addition to straw (Nst) was studied to evaluate the transformations of Mn in soil using different extraction methods at the 5 locations. There was a general reduction in the pH during the experiment. Soil acidification caused by mineral N fertiliser increased the bioavailable Mn forms under NPK treatment. This Mn was mobilised from soil reserves, leading to depletion of Mn sources. Application of SS and FYM led to an increase in non-bioavailable Mn fractions, while the expected increase in biologically available Mn was not observed. As the high pH of soil limits Mn availability, foliar Mn application can be recommended for agricultural practice in high-pH soils. On the contrary, liming can be recommended for low-pH soil with high bioavailable Mn content to mitigate the risk of Mn toxicity.

Several phosphorus (P) extraction tests are being used as soil P tests, but many studies have shown that the correlation of extractable P with plant yield and P uptake varies and sometimes is poor. Infinite sink extraction methods may be superior in estimating plant P availability. Soil P tests were evaluated for their power in determining plant-available P pools. Thirty arable soils covering different soil groups were tested for soil characteristics and extractable P pools. Rye was grown on these soils for six weeks and analysed for shoot yield and shoot P concentrations. Correlations between soil P concentrations, shoot yield and shoot P content were investigated. Extractable P pools mostly significantly correlated with soil pH, texture and amorphous iron oxide content. High and significant correlations were found among most of the extractable soil P pools, except for calcium acetate lactate (CAL)-extractable P. In contrast to previous studies, diffusive gradients in thin films (DGT)-extractable P employed in our pot experiment did not perform better than other extraction methods in correlating with plant available P and uptake, likely because water availability was not a limiting factor of P diffusion. Plant-available P in the soils investigated in this study was controlled by P quantity (i.e. the amount of adsorbed P) and P intensity (i.e. the soil solution P). We conclude that the advantage of infinite sink extraction methods over equilibrium-based techniques becomes less apparent if P is not strongly intensity-controlled and water availability is not a limiting factor of P diffusion.

The antioxidative protection in leaves of four winter wheat ( Triticum aestivum L.) varieties with different field drought resistance was studied under severe recoverable soil drought at seedling stage by withholding irrigation for 7 days (57–59% leaf water deficit) followed by rewatering. A 3-fold raise in electrolyte leakage and a sharp increase in proline accumulation corresponded to drought severity. Hydrogen peroxide content and catalase (CAT) activity were maintained low under stress. Peroxidase (GPX) activity increased, whereas superoxide dismutase (SOD) activity only slightly changed. The content of ascorbate and low-molecular thiols diminished under severe drought and was restored in recovery. Malondialdehyde level was not changed significantly in drought-treated plants but raised after re-watering. In recovery CAT activity became significantly higher whereas GPX activity diminished. Three isoforms of SOD, one of catalase and three of GPX were revealed. Proline accumulation had a predominant role in drought response. As for varieties, drought sensitivity or tolerance was not necessarily correlated with differences in the antioxidative response at early vegetative stage.