# Application of Fly Ash Obtained from the Incineration of Municipal Solid Waste in Agriculture
## 5 The Impact of Using MSWI in Agriculture  
Of the total amount of ash generated, approximately 1.38 billion tons are used in agriculture [55; 56]. The application of fertilizers on the soil determined the degradation of agricultural lands over time (1.9 \(\times\) 10\({}^{9}\) ha of land are degraded), their surface increasing in the period 1991-2011 from 15% to 25% [57]. Improving the quality of degraded lands can be done by using biofertilizers that are friendly to the soil and the environment [58; 59]. The acidic pH of degraded soils can be \begin{table}
\begin{tabular}{c c c} \hline \hline
**Fly Ash Concentration (\%)** & **pH** & **EC \(\upmu\)s/cm** \\ \hline
0 (Soil only) & 6.65 & 281 \\
10 & 6.72 & 288 \\
20 & 6.72 & 296 \\
30 & 6.9 & 300 \\
40 & 6.91 & 308 \\
50 & 6.96 & 358 \\
100 (Fly ash only) & 7.56 & 600 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The values of pH and conductivity of the soil sample at different concentrations of ash added to the soil (data from [54]). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Fly Ash** & **pH** & **EC** & **CEC** & **OC** & **OM** & **WHC** \\ \hline
0 & 7.0 & 210 & 2.35 & 0.58 & 0.99 & 33.68 \\
1 & 7.5 & 265 & 1.78 & 0.54 & 0.93 & 34.69 \\
2.5 & 8.1 & 265 & 2.56 & 0.60 & 1.03 & 33.75 \\
5 & 8.0 & 280 & 2.48 & 0.58 & 0.99 & 36.13 \\
10 & 8.10 & 320 & 3.0 & 0.64 & 1.10 & 39.93 \\
15 & 8.2 & 346 & 2.82 & 0.73 & 1.26 & 42.93 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Physical properties of soil mixed with ash (data from [50]). alkalized by applying ash to the soil due to the hydroxides and carbonate salts of Ca and Mg contained in fly ash [47; 52; 56; 57], thus replacing the lime used to reduce soil acidity, and CO\({}_{2}\) emissions and global warming are reduced [56; 57; 60; 30]. One ton of fly ash could capture up to 26 kg of CO\({}_{2}\), i.e., 38.18 tons of fly ash per ton of sequestered CO\({}_{2}\)[61; 30]. Adding fly ash to soil in different concentrations is useful for plant growth and for sustainable agriculture, and is a good soil amendment [62; 61]. According to [PERSON] et al. [63], the application of ash in sandy soil increased the amount of water available for plants. Due to the content of nutrients in the soil: magnesium, calcium, phosphorus, potassium, and sulfur [22; 64], ash can replace chemical fertilizers [5; 65; 37; 58; 66]. When applying the ash to the acid soil, the heavy metal content of the soil and fly ash mixtures was below the acceptable limits [66; 67; 68; 69; 70]. The amount of ash applied to the soil must be calculated according to the resistance of the plants, the plant species that grow on the respective soil, and the type of soil [71; 72; 73]. According to [PERSON] [59], the salt content of an ash pond decreases after approximately 2-3 years, no longer being dangerous for soil and plants [74]. The concentration of salts in fresh ash decreases over time [59; 75; 76]. According to [73], it is recommended to apply an amount of MSWI fly ash lower than 5-10% to the soil, depending on its acidity and the plants growing on it. Continuous application of chemical fertilizers on soils can decrease crop productivity [17; 22; 40]. At fly ash doses ranging from 20 tons/hectare to 100 tons/hectare, the yield increase was 20-30% [12]. Applying ash to the soil together with organic manure brings beneficial nutrients to agricultural crops, increases soil pH, and increases crop yields. Adsorption of heavy metals is dependent on ash particle size, increasing with the decrease in bottom ash particle size [77; 78; 79]. The addition of a concentration of 5-10% fly ash increased the content of N, S, Ca, Na, and Fe of the soil; K uptake by plants was reduced; soil compaction was reduced; pH increased; the soil's bulk density decreased; water retention capacity increased; soil texture improved; soil fertility and productivity improved; and boron mobility and availability decreased [53; 56].