Carbon Stock, Biomass Production Between Rows and Soil Attributes
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Environmental benefits of agroforestry AGROFORESTRY SYSTEM BENEFITS TO ENVIRONMENT: CARBON STOCK, BIOMASS PRODUCTION BETWEEN ROWS AND SOIL ATTRIBUTES Abdo MTVN1*, Siqueira CCZ2, Chiba MK2, Santos GXL1, Rotta M3, Rosa JM3, Martins ALM1, Pissarra TCT4, Fabri EG2, Chaves TH1 (1) Polo Centro Norte- , Agencia Paulista de Tecnologia dos Agr Instituto Municipal de Ensino Superior IMES, Catanduva, SP, Brazil, (4) Departamento de Engenharia Rural, UNESP, Campus de Jaboticabal,SP, Brasil *Corresponding author: [email protected] Abstract Gully erosion stabilization started in 1997 to restore water flow and control soil erosion with four ponds construction. In 2011 an agroforestry system was planted in the edges under four treatments: T1-Mower, trees planted in hollows, spacing 3 x 2m, no plantation between rows; T2-herbicide, trees in hollows, 3.5 x 2 m, maize between; T3-Plough, harrow, scarifier, trees in furrows, 3.5 x 2 m, maize between; T4-Plough, harrow, scarifier, trees in furrows, 3.5 x 2 m, nothing between rows. Treatments influenced biomass between rows, trees carbon stock and soil properties. Trees C stock in 2015 was T1-6.4 t ha-1, T2-8.31 t ha-1, T3-4.84 t ha-1 and T4- 4.41 t ha-1. In 2017 C stock was T1-104.21 t ha-1, T2-44.91 t ha-1, T3-39.2 t ha-1 and T4-29.54 t ha-1, vegetation between rows C stock was: T1-103.56 g ha-1,T2-199.11 g ha-1, T3-147.77 g ha-1 and T4-85.14 g ha-1. Also soil OM, K, P, Mg, Ca, sum of bases, CEC, pH, and base saturation at 0-20 cm increased. Keywords: no tillage, carbon stock, tropical trees, soil attributes, Bixa orellana Introduction Agroforestry Systems (AFS) are important tools to restore degraded areas once they can induce the restoring process of vegetation and soil including trees to agricultural production ensuring biodiversity of the ecosystem and optimizing land use. Integrating forestry with food production and minimizing intensive land use compared to monoculture it also generates income and food production (Abdo et al. 2008). Siqueira (2017) also agrees that AFS generates extra income and allows diversified production in reforested area due to use of agricultural crops, shrub and tree species in the same physical space, with the possibility of including animal husbandry. According to the author species consortium can improve soil conditions, water quality, increase biodiversity and carbon sequestration. This crop diversification leads to a significant improvement of the physical, chemical and biological properties of the soil through nutrient cycling and erosion control. Also the use of trees can contribute significantly to reduce carbon emissions and mitigate climate change since their maintenance reduces emission of carbon as CO2 dioxide, the main source of emissions of greenhouse gases in tropical countries. According (2006) Brazil is a privileged country to reverse global climate change process by carbon sequestration through reforestation since it has climatic and technological conditions suitable for forest production but projects that measure forest related to carbon sequestration are necessary. The annatto (Bixa orellana L.) is a Bixaceae family plan, originally from tropical America, widely cultivated as a monoculture in Brazil and was used in this agroforestry system as part of the semi-arboreal component. Its seeds are valuable for producing pigments that are used as natural colorant in food, pharmaceutical and cosmetic industries with commercial value (Mendes et al. 2005). So this specie was chosen in order to optimize land and generate extra income (Fabri et al. 2015). 237 4th European Agroforestry Conference Agroforestry as Sustainable Land Use Environmental benefits of agroforestry This restoration project took place at the Polo Regional Centro Norte-APTA a research center, . The area had no soil conservation practices and excess of runoff due to cattle tracks depth towards the water in the lower part of the area resulted in a gully with approximately 700 meters long and in some places up to 15 meters deep. To stop the erosion, four dams and four sunken ponds were built perpendicular to the erosion direction in 1997 and 1998. Each pond was connected to the next one by concrete overflows channels to prevent channel erosion and stabilize the area. The following step to control erosion process and establish environmental sustainability was to restore the vegetation cover what was done with the implantation of a Agroforestry System in the edges of the pounds and a reforestation with native tree species in the spring. Materials and methods Characterization of the study area The AFS area is in Polo Centro Norte- APTA, Pindorama, SP, Brazil. An agricultural research center with total 532 ha and 144 ha of forest. The coordinates are 48 55 'W and 21 13' S, Koeppen Aw climate (tropical rainy), altitudes from 498 to 594 m (Lepsch and Valadares 1976). It is a transition between Cerrado and Atlantic Forest biomes (IBGE 2013). The predominant land use are cane sugar, citrus, mango, guava, tomato and pasture (Cavichioli et al. 2008) and with ultisols very susceptible to erosion (Vieira et al. 1999). The restoration of riparian vegetation on the edges of the ponds was done with an agroforestry system under different managements from a minimum interference on the soil (T1) to intensive tillage and no vegetation protection (T4), planted in 2011 with four parcels with 10 rows and 7 plants. Treatments were: T1 (Mower coupled to the tractor, trees planted in hollows, spacing 3 x 2 m without cultivated or fertilization between lines); T2 (herbicide, planting in hollows, 3.5 x 2 m spacing, maize cultivated between lines); T3 (Plough, Harrow, scarifier, planting trees in furrows, 3.5 x 2 m spacing, with maize between lines); T4 (Plough, Harrow, scarifier, planting trees in furrows, 3.5 x 2 m spacing, with no plantation between lines). Trees survey All trees were measured in January 2015 and in 2017.The annatto also in 2014. Height was measured with graduated wooden ruler and circumference at breast height (CBH) with a graduated tape. To estimate above tree biomass an indirect method developed by ICRAF (Arevalo et al. 2002) was used and results are in tons of carbon per hectare (C t ha-1). Biomass between rows To determine plant biomass between rows 4 samples were taken for each treatment plot using a sample square metal with an area of 0.25 m2, randomly launched in the area. All vegetation above ground was collected and the samples were oven dried at 60 C with forced air circulation to constant mass according to Pitelli (2000). Soil analysis: fertility In 2011 before plantation soil fertility attributes were evaluated in the 0-20 cm depth layer and two samples were composed by treatment (AFS1, AFS2 and AFS3). Samples were conditioned in plastic bags, identified and sent for determination, according to Raij et al.(2001): phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), active acidity (pH in calcium chloride), potential acidity (H + Al), sum of bases (SB), cation exchange capacity (CEC) and base saturation (V%). In 2016, four samples composed of 20 sub-samples were obtained at soil depths of 0-20 cm and 0-40 cm in each treatment for determination of the same chemical parameters analyzed in 2011. Carbon and nitrogen levels A composed sample consisting of 10 simple samples was obtained at depths of 0-5, 5-10, 10- 20, 20-30, 30-40, 40-60, 60-80 and 80-100 cm (four replicates per treatment). C stocks (Mg ha- 238 4th European Agroforestry Conference Agroforestry as Sustainable Land Use Environmental benefits of agroforestry 1) were calculated for each layer by multiplying carbon content (%), soil densities (g cm-3) and layer thickness (cm), and were corrected by the Carvalho et al. (2009) method. Results The carbon stock for all live trees of the agroforestry system (AFS) in 2015 and 2017, the carbon stock of vegetation between trees rows in 2017 in all treatments and the value for soil carbon stock in 2017, for treatments 1, 2 and 3 are shown in Figure 1. All data is shown in tons per hectare (t ha-1). The carbon stock of trees and soil carbon in the native forest (t ha-1) were also calculated so it can be compared to trees carbon stock from 2015 and 2017. By September 2015 the soil organic matter and sum of bases had increased in all treatments from 2011. It was observed that soil attributes such as soil organic matter (SOM), potassium, sum of bases, phosphorus, magnesium, cation exchange capacity (CEC), pH, calcium and base saturation at the 0-20 cm depth layer also increased from the year of plantation 2011 to 2016 (Figure 2). Figure 1: Carbon stock of trees in 2015 and 2017, carbon stock of vegetation between AFS trees rows in tons per hectare (t ha-1) in four treatments of the Agroforestry System (AFS) compared to carbon stock of native forest trees in 2017 and AFS soil carbon (t ha-1) in treatments 1, 2 and 3 compared to Forest Soil Carbon (t ha-1). 239 4th European Agroforestry Conference Agroforestry as Sustainable Land Use Environmental benefits of agroforestry Figure 2: Soil attributes in 2011 before AFS and in 2016, compared to forest soil (Siqueira 2017). The annatto (Bixa orellana) was also influenced by plantation techniques. Table 1 shows production and carbon stock of the specie in 2012 and 2014. Table 1: Seeds weight (SW) in g, productive trees (PT) and total fruits (TF) in 2012, and2014 and total of living trees (LT) and Carbon stock (CS) in 2014 under four different treatments (T1, T2, T3 and T4), Variation Coefficient (VC) and General Mean (GM).