# Application of Fly Ash Obtained from the Incineration of Municipal Solid Waste in Agriculture
## 6 The Effect of Using Fly Ash on Plant Development  
Soil micronutrient deficiency can be improved by adding certain concentrations of MSWI to the soil, thus helping plant development [16; 40; 53; 56; 97]. The addition of a quantity of MSWI ash lower than 10% of the weight of the acid soil, changed the respiratory intensity of the soil, and the soil microbes were activated by the release of CO\({}_{2}\)[98]. Some elements such as As, B, Mo, Se, and V can accumulate in the plant tissue [96]. Alkaline pH fly ash applied to acidic soil helps the development of crops and provides the micronutrients and macronutrients needed by plants, vegetables, and grains [56]. Plant biomass increased in fly ash-applied soil by 11.6-29.2% at lower application rates (<25% of soil mass) and decreased by 45.8% at higher application rates (50-100%) due to heavy metal toxicity [56]. Grain growth in soils treated with ash was similar to that in soils treated with phosphorus and potassium fertilizers, indicating that ash from waste incineration can provide essential nutrients for plant growth [49]. Plant growth was twice as high in ash-applied \begin{table}
\begin{tabular}{c c c} \hline \hline
**Physical Characteristics** & **Fly-Ash** & **Soil** \\ \hline Bulk density (g cc\({}^{-1}\)) & \textless{}1.0 & 1.33 \\ Water-holding capacity (\%) & 35–40 & \textless{}20 \\ Porosity (\%) & 50–60 & \textless{}25 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Physical characteristics of fly ash and soil (data from [30]). soils as compared to ash-free soils [51, 52]. At MSWI ash concentrations ranging from 20 ton/ha to 100 ton/ha, plant yield increases were 20-30% [21]. According to [66], the application of an amount of ash of 5-10% is recommended to have a positive effect on crops and acid soils. The addition of fly ash as a substitute for chemical fertilizer due to the content of phosphorus and potassium in sandy soils increased the production of clover, rye, barley, canola, rice, soybean, sunflower, wheat, tomato, and carrots [96]. According to [23], the addition of ash (125 MT ha\({}^{-1}\)) on acid soils (pH 6.0) improved the yield of crops of alfalfa, millet, beans, corn, cabbage, onions, tomatoes, potatoes, sorghum, and lettuce. Onion leaves increased when a quantity of 5 t/h ash was added to the soil [51]. The production of rice and wheat was improved in the soils to which an amount between ash of 10 and 20 t ha\({}^{-1}\) was added. The addition of ash to the soil led to a high growth yield after six months for the following crops: _Eucalyptus globulus_, _Neem (Azadirachta indica)_, _Custard apple (Anmona squamosa)_, and _Jamun (Syzygium cumini)_[96]. High peanut yields were obtained when BA bottom ash was added at a rate of 15 kg/m\({}^{2}\) of soil [77]. Fly ash soil mixture concentrations from 5 to 10% were beneficial for chili plant growth and yield; this addition improved the soil with nutrients and improved soil texture and fertility, resulting in good plant development, water retention capacity, and soil pH improvement [73]. The application of a quantity of 20% ash (_w/w_) [59] led to an increase in the concentration of nutrients N, P, K, Ca, S, Mg, Na, and Zn in the soil and their absorption by rice; it was found that an improvement of Si content, an improvement of soil fertility, and the absorption of nutrients in oilseed crops helped plant roots develop better, according to [PERSON] [30]; in soil to which ash was added [99], the yield of agricultural crops increased; the silicon content of rice plants [100] increased; and the yield of corn, sunflower, soybean, tomato, chili, and hot pepper crops increased [54]. The elemental analysis of the onion bulb showed that Na was unaffected, while the content of K and P gradually increased with the increase in the concentration of ash applied to the soil, and the concentration of iron remained unchanged due to the changes brought by the ash [50]. According to [PERSON] et al.