2.6. Application of biochar in agricultural production

Currently little information exists in the literature if biochar addition to soil as organic amendment can reduce the plant uptake of trace-elements and reduce toxic metals bioavailability to edible plants. Such practice, if found effective, can assist in management of contaminated agricultural and urban soils from current and past use of municipal SS and might be also useful in mining reclamation. Acidification can affect both the soil biota and biogeochemical processes, thus decreasing agricultural production [52, 53]. Biochar has been reported to modify soil quality characteristics, thereby increasing crop yields [54]. Because it is usually alkaline in nature, biochar can increase the pH of acidic soils [55, 56]. Furthermore, biochar application has also been promoted as a means of contributing to the mitigation of climate change by reducing soil N2O emissions [53, 57, 58]. Biochar addition changed soil chemical properties, including increasing soil pH, total nitrogen (TN), total carbon (TC), C/N ratio, and cation-exchange capacity (CEC), and shifted the bacterial community composition. As biochar has been considered unlikely to be used by soil microbes [59], and it cannot directly impact soil microbial community. Therefore, biochar may affect soil microbial community via improving soil chemical properties [53].

When used in acidified soil amelioration, biochar can increase crop yield through improving soil chemical conditions and changing the availability of nutrients. It can also impact soil microbial community by increasing diversity of soil microbes and changing relative abundances of their taxa) via changing soil chemical properties, thus influencing soil nutrient (e.g., C, N) cycling and controlling greenhouse gas emissions. By contrast, biochar can also enhance soil N losses to the atmosphere by stimulating both nitrification and denitrification, thus decreasing the efficiency of N-fertilizer utilization. Therefore, the effect of biochar on the efficiency of N fertilizer should be considered when it is widely recommended as soil amendment [53].

#### 2.7. Animal manure and agricultural waste application: An overview

2.5. Trace metals in animal manure

52 Agricultural Waste and Residues

potential or within 1000 feet (305 m) of municipal wells [50].

Animal manure is a source of valuable plant nutrients, but also a source of air and soil pollution and a threat to aquifers and surface waters unless managed carefully to minimize nutrient loss [48]. In addition, animal manures such as municipal SS is a source of trace metals [49] that might accumulate in edible plants when SS is used as an organic fertilizer and might also contaminate our natural water resources with trace metals. To avoid direct leakage to water abstraction plants or groundwater, manure must not be applied 50 feet (15 m) from potable water wells and 200 feet (60 m) uphill of conduits to groundwater. Furthermore, special care must be taken when applying manure to fields with high leaching

Figure 5. Pharmaceuticals used in animal feeding operations to protect against bacterial and disease infection.

Studies carried out by Gondek et al. [51] revealed that composting of organic materials has a significant effect on changes in mobile forms of heavy metals. The authors found that biochar and municipal SS added to maize straw immobilized Cd and Pb soluble forms due to addition

of biochar, whereas maize straw and SS alone did not impact cd and Pb mobility.

Gómez-Muñoz et al. [60] reported that, when diverse types of urban waste (human urine, sewage sludge, composted household waste) and agricultural wastes (cattle slurry, farmyard manure and deep litter) applied annually for 11 years (at normal and accelerated rates), soil water retention and total carbon improved. Cattle manure, sewage sludge and composted household waste increased soil total N by 13–131% compared to the mineral fertilizer (NPK). The interaction of biochar and compost used in agricultural practices affect each other's properties. Biochar could change the physicochemical properties, microorganisms, degradation, mummification and gas emission of composting, such as the increase of nutrients, cation exchange capacity (CEC), organic matter and microbial activities. Composting and addition of animal manure to biochar could change the characteristic properties of biochar such as its surface polar and non-polar attractions sites, ion-exchange sites, and electrostatic attraction functional groups (Figure 6), such as the improvement of nutrients availability, CEC, functional groups on biochar surface and soil organic matter (OM). These changes would potentially improve the efficiency of the biochar and remediation of pollution [61].

3.1.1. Research findings

(Figure 8).

of three replicates std. error.

positive effect on the growth and yield of tomato.

Soil Weight of fruits, g Plants<sup>3</sup>

Plants grown in soil fertilized with CM had 8.2, 15.8, and 1.3 kg fruits/3 plants in harvest 1, harvest 2, and harvest 3, respectively (Table 1). Whereas, biochar added to CM, HM, and NM native soil did not alter tomato yield in harvest 1 (P > 0.05). Accordingly, the synergistic effects of biochar mixed with soil amendments used in this study was not observed after biochar addition in harvest 1. This could be due to the low amount of biochar (1% w/w) used in each treatment. Results of harvest 1 also revealed that the addition of biochar to SS and YW treatments significantly increased fruit yield from 5.2 kg and 3.9 to 6.3 and 5.7 kg/3 plants, respectively, indicating a positive effect of biochar on the growth and yield of tomato grown in SS and YW treatments. In harvest 2, plots fertilized with HM mixed with biochar revealed a significant increase (P < 0.05) in tomato yield. Whereas, biochar added to other soil treatments did not promote tomato yield (Table 1). In harvest 3, the synergistic effect of biochar was observed in HM and NM native soil (Table 1). However, total weight of tomato fruits collected after three harvests presented in Figure 7 revealed that HM and YW amended with biochar significantly (P < 0.05) increased tomato yield compared to other treatments indicating a

Biochar and Animal Manure Impact on Soil, Crop Yield and Quality

http://dx.doi.org/10.5772/intechopen.77008

55

Overall tomato three harvests, the synergistic effects of biochar was only observed in HM and YW amended soils (Figure 7). Total marketable tomato yield of biochar amended soils was increased by 63 and 20% in HM and YW treatments, respectively compared to other soil treatments. Regardless of soil treatments, it could be concluded that harvest 2 had the greatest yield and greatest number of fruits compared to the other two harvests

Treatment Harvest 1 Harvest 2 Harvest 3 CM 8145.3 413 15806.2 1227 1326.1 354 CM-Biochar 8261.5 218 14761.4 937 1218.6 158 HM 4932.7 356 8423.8 1154 839.7 360 HM-Biochar 4901.9 556 15623.2 1644 2618.7 466 NM 744.7 555 14555.7 597 534.7 353 NM-Biochar 4077.4 94.3 12782.2 939 2913.6 278 SS 5139.1 187 16094.9 566 1505.9 347 SS-Biochar 6287.7 432 13858.8 274 625.2 166 YW 3925.7 96 13636.5 1285 690.4 503 YW-Biochar 5711.9 380 14788.6 1244 1466.6 503

Statistical comparisons were carried out among soil management practices using SAS procedure. Each value is an average

Table 1. Average weights of tomato fruits collected at three harvests from plants grown under 10 soil management

practices at the University of Kentucky South Farm (Fayette County, Kentucky, USA).

Figure 6. Schematic diagram of biochar showing its electrostatic attraction sites, ion-exchange sites, polar and non-polar attraction sites collectively known as surface functional groups.
