Available plant nutrients in growth substrate depending on various lime materials used for neutralising bog peat
Department of Field Crops, Estonian Research Institute of Agriculture, Teaduse 13, 75501 Saku, Estonia; e-mail: email@example.com
In 1998–2000, the effect of local Estonian lime materials (oil shale ash, cement clinker dust, limestone meal, dolomite meal and their mixtures) used for neutralising acid bog peat on the contents of available plant nutrients (K, Ca, Mg) and on Ca:Mg, Ca:K, K:Mg ratios in peat substrate was investigated. The substrate were made on NPK and NP backgrounds. Lime materials, the Ca:Mg ratio of which varied between 3.4–16.7:1, were applied at a rate of 8 kg (in some variants 6 and 10 kg) per m³ peat. The substrate were analysed 2 and 4 weeks after their production.
The pHKCl of growth substrate became stable almost within 2 weeks. Dolomite meals neutralised peat acidity approximately by 0.5–0.7 units less than the same rate of dusty lime fertilisers. The higher the Mg-content in lime material, the weaker its neutralising effect. While using a 1:1 mixture of limestone and dolomite meal, the content of available Mg in the substrate was sufficient for plant growth and it was possible to leave out the application of Mg-fertiliser to the substrate. The Ca:Mg ratio in growth substrate was considerably broader than in lime materials and depended significantly on the type of lime. The content of available Ca in substrate increased relatively more than that of available Mg. Under the effect of dusty lime fertilisers the Ca:Mg ratio had shifted in favour of Ca by 1.2–1.4 times, in the case of carbonate rock meals the preponderance of Ca had increased by 3.6–3.9 times. The best variants for neutralising peat acidity in the given research were as following: 1:1 mixture of limestone meal and dolomite meal and 1:1 mixture of clinker dust and dolomite meal. In these cases the contents of Ca, Mg and K and their mutual ratios in the substrate corresponded in the best way to the limit values needed for the optimum growth of greenhouse vegetables.