Mineral soil conditioner requirement and ability to adjust soil acidity

Abstract

Abstract Mineral soil conditioners (MSCs) are used to regulate soil acidity and improve soil quality; they are often made in sintering potassium feldspar, limestone, or dolomite, and are alkaline materials rich in silicon, calcium, potassium, and magnesium. The key point of how to apply them into farmlands is their ability to adjust soil acidity and the MSCs requirement (MSCR). In this study, inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis and X-ray diffraction (XRD) were firstly used to determine the elemental and phase compositions of the MSCs in order to establish its equivalent relationship for the depletion of soil activity (H+) and its conversion relationship with CaCO3. Secondly, the soil culture method and the improved Shoemaker Mclean Peatt–Double Buffer (SMP–DB) method were compared using a group of 14 typical acid soils in MSCR. It is investigated that the MSCs contained four alkali/alkaline earth–metal elements: Ca, Mg, K, and Na in the bound aluminosilicate form (Ca2MgAlSi2O7, Ca3(SiO3)3, KAlSiO4, and KAlSi2O6); and the depletion of 2.31 mol of H+ required 100 g of MSCs and the amount of Si–Ca–K–Mg MSC needed to deplete the same quantity of H+ was only 0.87 times that of CaCO3. Based on the calculations by using the SMP-DB method and the soil culture method, the MSCR for treating the 14 typical acid soils were in the range of 0.56–8.27 t hm−2 and 0–10.8 t hm−2, respectively. Data from both methods were highly correlated with each other and there was a good linear correlation between them, and the equation: $${{MSC}_{R}}^{{\prime}}=30.29d-0.77$$ MSC R ′ = 30.29 d - 0.77 could be used to calculate the MSCs requirement. The recommended MSCR was approximately 4–8, 2–6, and 1–3 t hm−2 when soil pH < 4.50, 4.50 < pH < 5.50, and pH > 5.50, respectively. The experimental and computational methods established in this study could serve as the scientific basis and theoretical guidance for the production and agricultural use of MSCs.