**5. Evaluation of soil fertility and lime and gypsum application**

Sugarcane extracts and accumulates large amounts of nutrients from the soil because it produces large amounts of biomass. In evaluations carried out in small properties of the Zona da Mata region, the authors found that to produce 120 tons of natural matter per ha (about 100 t of industrializable culms), the accumulation of nutrients in shoots is approximately 150, 40, 180, 90, 50, and 40 kg of N, P, K, Ca, Mg, and S, respectively. In the case of iron, manganese, zinc, copper, and boron, accumulation in shoot biomass for a production of 120 t is around 8.0, 3.0, 0.6, 0.4, and, 0.3 kg, respectively [1]. Because of this high nutrient removal, it is necessary to know the nutrient supply capacity of the soil to complement it with fertilization if necessary. On the other hand, if toxic levels are found, the concentration of these elements is reduced by applying limestone and gypsum. The availability and presence of toxic levels of nutrients in soil are typically evaluated by chemical analysis of the topsoil. Knowledge of the history of the area is also of great value, especially fertilization and whether or not there were symptoms of deficiency or toxicity in previous crops.

Soil samples are typically collected at depths of 0–20 and 20–40 cm. The results of the analysis at 0–20 cm have been used to calculate the need for fertilization and liming, while those at 20–40 cm to calculate the need for gypsum. Because these are small areas, the authors have advised producers to collect soil samples using a hole

digger and straight shovel, as the use of a straight shovel decreases the variability of soil fertility indexes. Further details on sampling procedures, sample variability, sample drying, and comparison between chemical extractors can be found in Ref. [1]. As previously mentioned, most of the soils of the region are naturally acidic and present low saturation by basic cations such as calcium, magnesium, and potassium. Deficiency of these basic cations combined with high levels of aluminum, iron, and manganese has been detrimental to the growth of the root system and the entire plant. For these reasons, limestone and gypsum applications are recommended by the authors. Several materials have been used as soil acidity correctors, of which the most commonly used is dolomitic limestone. However, calcitic and magnesium limestone, as well as calcium and magnesium silicates (referred to as steel slags) are also used. Magnesium oxide content is around 8% in steel slag, while it is less than 5% in calcitic limestone, between 6 and 12% in magnesium limestone, and above 12% in dolomitic limestone. The efficiency of these products in correcting soil acidity depends on particle size, uniform distribution in the field, and soil water availability.

The most used soil analysis method in the region is the one that uses calcium acetate to determine H+ + Al+3. This extractor greatly underestimates the amount of H+ + Al+3, and results in underestimating the cation exchange capacity at pH 7.0 and the limestone dose. For these reasons, the authors have recommended raising the dose of limestone by 1.5–2.0 times. For sugarcane grown in small farms, the recommendation is to increase base saturation (V) to 60%. The limestone dose (LD) when using the base saturation method is calculated by the following equation (Eq. (1)):

$$LD\ \left(t\ ha^{-1}\right) = \left[\left(\left(60 - V\right) \times T\right] + RTNP\tag{1}$$

where V is the current base saturation of the soil, T is the cation exchange capacity at pH 7.0, and RTNP is the relative total neutralizing power of the corrective used.

Dolomitic limestone is recommended when magnesium content at 0–20 cm is less than 0.40 cmolc/dm3 of soil. On the other hand, if magnesium content at 0–20 cm is greater than 0.40 cmolc/dm3 of soil, the recommendation is to use the corrective that has the lowest price per ton of RTNP in the crop. Thus, an economic factor is included in the decision making regarding the type of limestone to be used. The use of gypsum has been recommend based on the results of chemical analysis of the 20–40 cm layer. Gypsum has been applied when calcium content is less than 0.40 cmolc/dm3 of soil or aluminum saturation (m%) is higher than 20%. The usual recommended dose is one-third of the limestone dose (e.g., assuming that the limestone dose is 4.5 t per ha, then gypsum will be 1.5 t per ha). Limestone and gypsum are mixed for subsequent application to the soil. The application of gypsum will lead to the improvement of the root environment of the layers below the topsoil. This effect lasts for several years, which is the reason annual gypsum application is not necessary [1].

In small properties, the application of limestone + gypsum is typically done by hand. A recommended method for these small producers has been to delimit a square or rectangle with the mixture of limestone + gypsum and apply a volume corresponding to the recommended dose in the area. For instance, if the recommended dose was 6000 kg (4500 kg of limestone +1500 kg of gypsum per ha) and the density of the limestone + gypsum mixture is 1.25 kg/L, then 4800 L per ha or 0.48 L per m<sup>2</sup> should be applied. Another alternative for small producers to apply limestone + gypsum by hand would be to demarcate areas of 25 m<sup>2</sup> with the mixture itself and apply 12.0 L of limestone + gypsum.

Plowing and harrowing is typically done after the application of limestone + gypsum to incorporate the products into the soil. In most small farms, subsoiling (decompacting soils or breaking compacted layers) has been recommended after

**27**

**Table 4.**

*and 120 days after plant emergence (DAE).*

*Sugarcane Production Systems in Small Rural Properties DOI: http://dx.doi.org/10.5772/intechopen.84975*

plowing and harrowing. This recommendation is based on the land use history of the area, the traffic of machines, implements and animals, the presence of crusts on the surface of the land, and the shallow root system of the natural vegetation. Although it may be an additional burden for the producer, the presence of densified or compacted layers has harmful consequences on water absorption, mineral nutri-

As previously mentioned in item 4 (implantation of sugarcane plantation), one of the advantages of planting the "one-and-a-half-year sugarcane" is the possibility of a green fertilization prior to the planting of sugarcane. Among the main desirable characteristics of plants used for green fertilization are the following: the possibility of using mechanization from sowing to the harvesting of seeds, the ability to associate with nitrogen-fixing bacteria, rapid growth to control weeds, having mechanisms, or being able to synthesize compounds that help control pests (e.g., nematodes) and diseases, no dormant seeds, and a vigorous and deep root system that assists in the recycling of nutrients from the deepest layers and in soil decompaction. Another aspect to be considered is the supply of organic and mineral substrate to soil microorganisms. Thus, green fertilization also contributes to the improvement of the biological quality of the soil [2–4]. Several legumes have these characteristics, but there is generally a preference for *Crotalaria juncea* in South Central Brazil [1]. In the studies conducted by the authors of this chapter in the Zona da Mata region, green fertilization with *Crotalaria juncea* prior to planting the "one-and-ahalf-year sugarcane" resulted in increased yield in the plant-cane and first regrowth

cycles, which together ranged from 20 to 26 t of culms per ha. In a multiyear analysis, the costs of green fertilization corresponded to 6–12 t of industrializable culms per ha. Thus, the increase in yields covered the costs of growing the legume. Furthermore, there are studies in which increased yields of sugarcane as a result of green fertilization with *Crotalaria juncea* were higher. For instance, in studies conducted over several years in the city of Sales Oliveira, state of São Paulo, Ref. [5] reported increased yields of industrializable culms ranging from 26 to 40 t per ha. *Crotalaria juncea* exhibits high growth rates, which result in increased plant height, as shown in **Table 4**. High growth rate associated with increased plant

**DAE Plant height LAI DM accumulation DM accumulation rate**

 84 2.1 2.2 73 178 3.6 4.1 127 192 6.5 7.8 247 247 8.3 11.9 273 313 9.4 14.2 153 328 11.3 15.5 87 342 8.9 16.2 47

*Plant height, leaf area index (LAI), dry matter accumulation (DM accumulation), and dry matter accumulation rate (DM accumulation rate) in shoot biomass of Crotalaria juncea at 30, 45, 60, 75, 90, 105,*

**/m2 (t/ha) (kg/ha/day)**

**(cm) m2**

tion, crop development, and longevity of the sugarcane plantation.

**6. Green fertilization in "one-and-a-half-year sugarcane"**

*Multifunctionality and Impacts of Organic and Conventional Agriculture*

acetate to determine H+

*LD* (*t ha*−1

H+

tive used.

than 0.40 cmolc/dm3

greater than 0.40 cmolc/dm3

digger and straight shovel, as the use of a straight shovel decreases the variability of soil fertility indexes. Further details on sampling procedures, sample variability, sample drying, and comparison between chemical extractors can be found in Ref. [1]. As previously mentioned, most of the soils of the region are naturally acidic and present low saturation by basic cations such as calcium, magnesium, and potassium. Deficiency of these basic cations combined with high levels of aluminum, iron, and manganese has been detrimental to the growth of the root system and the entire plant. For these reasons, limestone and gypsum applications are recommended by the authors. Several materials have been used as soil acidity correctors, of which the most commonly used is dolomitic limestone. However, calcitic and magnesium limestone, as well as calcium and magnesium silicates (referred to as steel slags) are also used. Magnesium oxide content is around 8% in steel slag, while it is less than 5% in calcitic limestone, between 6 and 12% in magnesium limestone, and above 12% in dolomitic limestone. The efficiency of these products in correcting soil acidity depends on particle size, uniform distribution in the field, and soil water availability. The most used soil analysis method in the region is the one that uses calcium

+ Al+3. This extractor greatly underestimates the amount of

) *=* [(60–*V*) *× T*] *÷ RTNP* (1)

 + Al+3, and results in underestimating the cation exchange capacity at pH 7.0 and the limestone dose. For these reasons, the authors have recommended raising the dose of limestone by 1.5–2.0 times. For sugarcane grown in small farms, the recommendation is to increase base saturation (V) to 60%. The limestone dose (LD) when using the base saturation method is calculated by the following equation (Eq. (1)):

where V is the current base saturation of the soil, T is the cation exchange capacity at pH 7.0, and RTNP is the relative total neutralizing power of the correc-

Dolomitic limestone is recommended when magnesium content at 0–20 cm is less

has the lowest price per ton of RTNP in the crop. Thus, an economic factor is included in the decision making regarding the type of limestone to be used. The use of gypsum has been recommend based on the results of chemical analysis of the 20–40 cm layer.

or aluminum saturation (m%) is higher than 20%. The usual recommended dose is one-third of the limestone dose (e.g., assuming that the limestone dose is 4.5 t per ha, then gypsum will be 1.5 t per ha). Limestone and gypsum are mixed for subsequent application to the soil. The application of gypsum will lead to the improvement of the root environment of the layers below the topsoil. This effect lasts for several years,

In small properties, the application of limestone + gypsum is typically done by hand. A recommended method for these small producers has been to delimit a square or rectangle with the mixture of limestone + gypsum and apply a volume corresponding to the recommended dose in the area. For instance, if the recommended dose was 6000 kg (4500 kg of limestone +1500 kg of gypsum per ha) and the density of the limestone + gypsum mixture is 1.25 kg/L, then 4800 L per ha or

Plowing and harrowing is typically done after the application of limestone + gypsum to incorporate the products into the soil. In most small farms, subsoiling (decompacting soils or breaking compacted layers) has been recommended after

should be applied. Another alternative for small producers to apply

Gypsum has been applied when calcium content is less than 0.40 cmolc/dm3

which is the reason annual gypsum application is not necessary [1].

limestone + gypsum by hand would be to demarcate areas of 25 m<sup>2</sup>

itself and apply 12.0 L of limestone + gypsum.

of soil. On the other hand, if magnesium content at 0–20 cm is

of soil, the recommendation is to use the corrective that

of soil

with the mixture

**26**

0.48 L per m<sup>2</sup>

plowing and harrowing. This recommendation is based on the land use history of the area, the traffic of machines, implements and animals, the presence of crusts on the surface of the land, and the shallow root system of the natural vegetation. Although it may be an additional burden for the producer, the presence of densified or compacted layers has harmful consequences on water absorption, mineral nutrition, crop development, and longevity of the sugarcane plantation.
