**4.1. Crop response upon the use of slaughterhouse organic residues (SORs)**

Combinations of 25% + 75%, 50% + 50% and 75 + 25% mineral fertilizer with organic fertilizer demonstrated significantly higher yields in several crop seasons compared with fertilization with 100% mineral fertilizer (**Table 1**). Sutton et al. [37] studied the effects of waste residue rates from ruminant animals and did not find differences in corn productivity among the rates or between mineral and organic fertilizers in 5 years of use. Despite the lack of significant difference, crop yields were always higher in organically fertilized plots.


T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. Means followed by the same letters per row do not differ among themselves by the LSD test at *P* < 0.05. "ns" indicates not significant by the *F* test at *P* < 0.05. Source: Romaniw [60].

**Table 1.** Crop yields affected by slaughterhouse organic and mineral residues in no‐till system.

Considering the six crop seasons accumulated (**Table 1**), the treatments with the highest productivities were T4 (75% SMF + 25% SOR) and T5 (50% SMF + 50% SOR), representing increases of 49.0% and 58.7% in relation to the control treatment (without SMFs and SORs), respectively.

Many authors [31, 38-40] have reported increases in crop yields due to the use of organic sources in fertilization. However, some of them can only be observed from medium‐term to long‐term courses due to the slow and gradual soil property change, as observed in Table 1, with changes among the fertilizer treatments observed only after the third crop.

Through cost‐benefit analysis (**Table 2**), we could identify that the increase in crop yield and the mineral fertilizer cost reduction, in response to the increase in SOR rates, reflected in increases in net earnings in comparison with SMF fertilization. With the application of the lowest SOR rate (25%), there were savings of 292.57 USD per hectare compared with the mineral fertilizer, but the maximum savings of 1170.27 USD per hectare was achieved with the application of 22 Mg ha−1 SOR along the 11 crop seasons.


\*Base values were obtained from SEAB [41]. T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. \*SMF rates were recommended according to cultivated crop and soil analysis, and the SOR rate was fixed at 2 Mg ha−1.

**Table 2.** Fertilization costs (SORs and SMFs) along the crop seasons.

#### **4.2. Soil organic matter (SOM) pools in crop systems affected by SOR application**

As soil organic matter (SOM) is closely linked to C, it is essential to note that it is found in highly variable situations in terms of level of decomposition, chemical composition, size, level of recalcitrance as well as chemical and physical protection. For this reason, fractionation methods were used (chemical or physical) to classify and quantify the effects of SOR applica‐ tion on the SOM pools. In addition, the use of SORs as fertilizers in the medium and long terms can increase TOC content and microbial activity, which results in the recovery of soil quality and increases crops' productive potential.

Analyzing the use of slaughterhouse waste over SOM pools, we could observe an increase in total organic carbon (TOC) stocks at the 0–20 cm layer through the use of a combination of 50% SOR + 50% SMF (**Table 3**). This increase was 33.8% higher than that in the control (without SORs and SMFs) and 28.8% higher than that in T2 (100% SMF). Previous studies developed by Filho et al. [42] and Zhang et al. [43] concluded that fertilization with organic waste in long‐ term experiments elevated soil carbon (C) and nitrogen (N) levels.

C‐CO2 Emissions, Carbon Pools and Crop Productivity Increased upon Slaughterhouse Organic Residue Fertilization in a No‐Till System http://dx.doi.org/10.5772/63123 229


long‐term courses due to the slow and gradual soil property change, as observed in Table 1,

Through cost‐benefit analysis (**Table 2**), we could identify that the increase in crop yield and the mineral fertilizer cost reduction, in response to the increase in SOR rates, reflected in increases in net earnings in comparison with SMF fertilization. With the application of the lowest SOR rate (25%), there were savings of 292.57 USD per hectare compared with the mineral fertilizer, but the maximum savings of 1170.27 USD per hectare was achieved with the

**Treatments**

with changes among the fertilizer treatments observed only after the third crop.

**Crops T2 T3 T4 T5 T6**

according to cultivated crop and soil analysis, and the SOR rate was fixed at 2 Mg ha−1.

term experiments elevated soil carbon (C) and nitrogen (N) levels.

**Table 2.** Fertilization costs (SORs and SMFs) along the crop seasons.

and increases crops' productive potential.

Beans 280.40 125.63 241.71 203.02 164.32 Soybean 240.86 125.63 212.06 183.25 154.44 Corn 529.65 125.63 428.64 327.64 226.63 Oats 301.51 125.63 257.54 213.57 169.60 Wheat 508.79 188.44 428.71 348.62 268.53 Accumulated 1861.22 690.95 1568.65 1276.09 983.52

**‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐U\$ ha−1‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐**

\*Base values were obtained from SEAB [41]. T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. \*SMF rates were recommended

As soil organic matter (SOM) is closely linked to C, it is essential to note that it is found in highly variable situations in terms of level of decomposition, chemical composition, size, level of recalcitrance as well as chemical and physical protection. For this reason, fractionation methods were used (chemical or physical) to classify and quantify the effects of SOR applica‐ tion on the SOM pools. In addition, the use of SORs as fertilizers in the medium and long terms can increase TOC content and microbial activity, which results in the recovery of soil quality

Analyzing the use of slaughterhouse waste over SOM pools, we could observe an increase in total organic carbon (TOC) stocks at the 0–20 cm layer through the use of a combination of 50% SOR + 50% SMF (**Table 3**). This increase was 33.8% higher than that in the control (without SORs and SMFs) and 28.8% higher than that in T2 (100% SMF). Previous studies developed by Filho et al. [42] and Zhang et al. [43] concluded that fertilization with organic waste in long‐

**4.2. Soil organic matter (SOM) pools in crop systems affected by SOR application**

application of 22 Mg ha−1 SOR along the 11 crop seasons.

228 Organic Fertilizers - From Basic Concepts to Applied Outcomes

T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. Means followed by the same letters per row do not differ among themselves by the LSD test at *P* < 0.05. "ns" indicates not significant by the *F* test at *P* < 0.05. Source: Romaniw et al. [54].

**Table 3.** Total organic carbon (TOC) contents and stocks in response to the use of mineral fertilizers and slaughterhouse organic waste applied in isolated and combined forms in no‐till system.

de Andrade et al. [44] observed higher increases in TOC in the second year after the application of sewage sludge biosolids in sugarcane, emphasizing that such effects could be further increased in subsequent years.

The contents and stocks of mineral‐associated organic carbon (MAOC) and the contents of particulate organic carbon (POC) presented different responses upon the fertilization treat‐ ments (**Table 4**).



T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. Means followed by the same letters per row do not differ among themselves by the LSD test at *P* < 0.05. "ns" indicates not significant by the *F* test at *P* < 0.05. Source: Romaniw et al. [54].

**Table 4.** Contents and stocks of particulate organic carbon (POC) and mineral‐associated organic C (MAOC) in response to the application of mineral fertilizers and slaughterhouse waste isolated and combined in no‐till system.



**Layer (cm) Treatments**

230 Organic Fertilizers - From Basic Concepts to Applied Outcomes

MAOC stock, Mg ha−1

[54].

**Layer (cm) Treatments**

**T1 T2 T3 T4 T5 T6**

5–10 1.17bc 1.06c 1.28bc 1.19bc 1.98a 1.79ab 10–20 2.15ns 2.29 2.20 2.10 2.29 2.97 0–20 5.35ns 5.53 5.52 5.42 6.02 6.15

0–5 9.41bc 6.97c 10.48abc 15.00ab 16.84a 15.39ab 5–10 7.54ns 9.11 8.17 8.05 8.14 9.06 10–20 13.79b 15.89ab 14.97ab 15.21ab 17.31a 15.07ab 0–20 30.74c 31.97bc 33.62bc 38.25abc 42.29a 39.51ab

T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. Means followed by the same letters per row do not differ among themselves by the LSD test at *P* < 0.05. "ns" indicates not significant by the *F* test at *P* < 0.05. Source: Romaniw et al.

**Table 4.** Contents and stocks of particulate organic carbon (POC) and mineral‐associated organic C (MAOC) in response to the application of mineral fertilizers and slaughterhouse waste isolated and combined in no‐till system.

0–5 1.29a 2.34b 2.74b 2.49b 2.72b 2.86b 5–10 0.89a 1.71bc 1.74bc 1.54b 1.89c 1.80bc 10–20 0.67a 1.61b 1.43b 1.28b 1.66b 1.68b

0–5 0.42a 0.67a 1.29b 2.07c 2. 2.33c 5–10 0.50a 0.69a 0.69a 1.93b 2.02b 1.95b 10–20 0.51a 0.67a 0.57a 1.54b 1.95b 2.03b

0–5 0.81a 1.48b 1.70b 1.57b 1.71b 1.80b 5–10 0.62a 1.20b 1.22b 1.08b 1.33b 1.26b 10–20 0.91a 2.21b 1.95b 1.75b 2.28b 2.30b 0–20 2.35a 4.88b 4.90b 4.40b 5.32b 5.36b

0–5 0.26a 0.42a 0.81b 1.31c 1.30c 1.47c 5–10 0.35a 0.48a 0.48a 1.35b 1.41b 1.37b 10–20 0.70a 0.91a 0.79a 2.10b 2.67b 2.78b

C‐OXP content, g kg−1

C‐HW content, g kg−1

C‐OXP stock, Mg ha−1

C‐HW stock, Mg ha−1

**T1 T2 T3 T4 T5 T6**

T1 = Absolute control (without SORs and SMFs); T2 = 100% SMF; T3 = 100% SOR; T4 = 75% SMF + 25% SOR; T5 = 50% SMF + 50% SOR; T6 = 25% SMF + 75% SOR. Means followed by the same letters per row do not differ among themselves by the LSD test at *P* < 0.05. "ns" indicates not significant by the *F* test at *P* < 0.05. Source: Romaniw et al. [54].

**Table 5.** Contents and stocks of C oxidizable by potassium permanganate (C‐OXP) and hot water (C‐HW) in response to the use of mineral fertilizers and organic residues from slaughterhouses applied alone or in combination under a no‐ till system.

For POC at the 0–20 cm layer, the treatments that provided the highest increases were T<sup>5</sup> (50% SMF + 50% SOR) and T6 (25% SMF + 75% SOR), with increments of 12.5% and 14.9%, respectively, in comparison with the control (**Table 4**). For MAOC at the same depth, the highest increases were also provided by T5 and T6, with increments of 37.6% and 28.5%, re‐ spectively, in comparison with the control. The increase and maintenance of labile SOM pool stocks are essential for the amelioration of soil quality and for the sustainability of crop systems, since they are essential for soil microbial activity [45].

The C‐HW content decreased with soil depth, suggesting a stratification profile in the soil (**Table 5**). This fact is already well reported in no‐till systems [46-48], and due to the addi‐ tion of SORs, this response was even more pronounced, leading to higher biomass‐C input from crop residues over the soil surface.

In addition, the SOR application in combination with SMFs increased the C‐OXP and C‐HW stocks regardless of the SMF combination. Considering the C‐OXP pool at the 0–20 cm layer, the treatments that provided the highest increases were T5 (50% SOR + 50% SMF) and T6 (75% SOR + 25% SMF), representing increases of 126.4% and 128.0%, respectively, in comparison with the control. For C‐HW at the same depth, the T5 and T6 treatments were also the ones that provided the highest increases, with increments of 310.7% and 328.2%, respectively, in comparison with the control.

This impact of the combinations of SORs and SMFs, in the short term, could be attributed to the increase of labile SOM pools, promoting higher soil biological activity [48]. The input of organic residues also plays an important role in soil aggregation [49] and higher C protection [50]. Similar results were also found by Kanchikerimath and Singh [51] and Rudrappa et al. [52] in the medium term (more than 5 years) in India.

Thus, fertilization with SORs favors soil microbial activity and stimulates soil organic matter mineralization [53]. Therefore, combinations of SORs and SMFs can lead to higher C inputs, and depending on the soil layer, they can even surpass the increments provided by isolated SMFs.
