Nutrient cycling in sugarcane. V. Potassium balance during four cropping periods

Foi acompanhado o balanço de K em 12 parcelas fertilizadas igualmente com K, 83 kg/ha por ciclo, determinando-se periodicamente K nas plantas e extraível no solo. Na cana-planta, foram medidos o aporte de K na água de chuva e a perda por drenagem profunda. Neste ciclo, a adubação e a diminuição do K não compensaram o K absorvido pelas plantas (174 kg/ha). Desse K, 88 kg/ha foram exportados com as canas, 77 kg/ha retornaram ao solo como cinzas, e 9 kg/ha permaneceram nas raízes e colmos subterrâneos. A perda por drenagem profunda, 7 kg/ha, foi sobrecompensada pelo aporte de 18 kg/ha de K pela água de chuva. A absorção de K pelas socas foi mais do que compensada pelo aporte na cinza e no fertilizante. Nos quatro ciclos, o balanço favorável de adubação (322 kg/ha) versus exportação (l70 kg/ha) resultou no aumento de K das cinzas (117 kg/ha) e extraível do solo (66 kg/ha). O balanço de K no solo fechar-se-ia admitindo-se a liberação de 28 kg/ha da fração não-extraível do solo.The balance of K in 12 field plots equally fertilized with K, 83 kg/ha per cycle, was followed by determining periodically plant and soil extractable K. For plant-cane, inputs of K in rain water and outputs through deep drainage were measured. During this cycle, fertilizer inputs and decreases in extractable K did not compensate K absorption by plants (174 kg/ha). Of this amount, 88 kg/ha were exported by the canes, 77 kg/ha returned to the soils as ashes and 9 kg/ha remained in the below-ground biomass. Deep drainage losses, 7 kg/ha, were overcompensated by rainwater input, 18 kg/ha. Potassium absorption by the ratoons was smaller than inputs from fertilizer and ashes. For the four cycles, a favorable balance of fertilizer inputs (332 kg/ha) versus cane outputs (170 kg/ha) resulted in increases in ashes (117 kg/ha) plus soil extractable K (66 kg/ha). The K balance in the soil would be closed considering the release of 28 kg/ha of K by the non-exchangeable fraction

Vegetation similarities on seven soils of caatinga

Neste estudo, foram observadas a flora e a densidade de todas as plantas em sete comunidades vegetais desenvolvidas em solos do semi-árido de Parnamirim, PE, quais sejam: Podzólico Vermelho-Amarelo Eutrófico latossólico, PE; Bruno Não-Cálcico, NC; Bruno Não-Cálcico litólico, NC; Planossolo Solódico, PL; Vertissolo, V; Regossolo Eutrófico profundo, REp e Regossolo Eutrófico raso, Rer. Por comunidade, foram amostradas 5 parcelas de 100 m2, para lenhosas, 20 subparcelas de 1 m2, para herbáceas, e 1 perfil de solo. Para comparar as comunidades utilizou-se o índice de Srensen. Os pares de comunidades PL-NC a PE-NC revelaram os mais altos índices de semelhança para densidade de lenhosas, e seus solos, grandes diferenças químicas e físicas. O par de comunidades PE-REp apresentou semelhança tanto para a densidade de herbáceas quanto para a densidade de lenhosas, o que pode ser explicado pelas similitudes desses solos. Os pares de comunidades NC-NC, V-NC e NC-V, apresentaram altas semelhanças para densidade de herbáceas.Flora and plant density were studied on seven communities developed on semi-arid soils at Parnamirim, Pernambuco, Brazil. The soils were classified as: Latossolic Eutric Red-Yellow Podzolic (PE); Non Calcic Brown (NC); Litolic Non Calcic Brown (NC; Solodic Planosol (PL); Vertisol (V); Eutric Regosol, deep phase (REp), and Eutric Regosol, shallow phase (REr). Each community had a sample composed by 5 plots of 100 m2, for woody plants, 20 subplots of 1 m2, for herbaceous plants, and 1 soil profile. The Srensen index was used to compare the communities. The pairs of communities PL-NC and PE-NC showed the highest similitude index for density of woody plants, and the soils large chemical and physical diferences. The pair of communities PE-REp showed similarities in relation to the density of woody and herbaceous species, which can be explained by the similarities in chemical and physical properties of the two soils. The pairs of communities NC-NC, V-NC and NC-V showed high similarities for the density of herbaceous species

Energetic and Economic Analysis of Spineless Cactus Biomass Production in the Brazilian Semi-arid Region

The Brazilian semi-arid region is marked by a variable spatial-temporal rainfall distribution, concentrated over a 3 to 4 month season. Limited water availability is the main obstacle to the production of forage plants of C3 metabolism (such as corn and soybeans) and C4 metabolism (such as sugarcane), as well as livestock. To mitigate this forage supply, the spineless cactus (SC) has been cultivated in the region, producing high biomass amounts in this harsh environment. Recently, this remarkable capacity to produce biomass has drawn the attention of the renewable energy sector, supported by recent studies demonstrating the feasibility of its biomass as a raw material for bioenergy production. However, before moving to commercial scale, it is necessary to demonstrate that large-scale production has energy and economic viability for clean energy investors. Thus, the objective of this article was to analyze the energetic and economic viability of forage cactus cultivation systems in the Brazilian semi-arid region. The data used were extracted from the literature, based on forage production. For the energy evaluation, the energy balance was performed and the energy efficiency, energy productivity, specific energy, and net energy metrics were applied. The financial feasibility analysis used the Net Present Value (NPV) and Internal Rate of Return (IRR). The energy balance revealed that the SC cultivation is viable for biomass commercial-scale production, with an energy efficiency of 3.36, an energy productivity of 0.25 kg MJ−1, a specific energy of 13.5 MJ kg−1, and an energy balance of 127,348 MJ ha−1. For the economic aspect, considering an attractive minimum rate of return of 8%, production also proved to be viable, in a time horizon of three years. The Net Present Value and IRR metrics were USD 2196 and the IRR was 46%, respectively. The results found are important to encourage new investments in rural properties in the semi-arid region, and cultivation in new areas proved to be an efficient alternative from an energy and economic point of view, in addition to collaborating for the energy transition to sustainable sources and in the mitigation of regional environmental impacts

Energetic and Economic Analysis of Spineless Cactus Biomass Production in the Brazilian Semi-arid Region

The Brazilian semi-arid region is marked by a variable spatial-temporal rainfall distribution, concentrated over a 3 to 4 month season. Limited water availability is the main obstacle to the production of forage plants of C3 metabolism (such as corn and soybeans) and C4 metabolism (such as sugarcane), as well as livestock. To mitigate this forage supply, the spineless cactus (SC) has been cultivated in the region, producing high biomass amounts in this harsh environment. Recently, this remarkable capacity to produce biomass has drawn the attention of the renewable energy sector, supported by recent studies demonstrating the feasibility of its biomass as a raw material for bioenergy production. However, before moving to commercial scale, it is necessary to demonstrate that large-scale production has energy and economic viability for clean energy investors. Thus, the objective of this article was to analyze the energetic and economic viability of forage cactus cultivation systems in the Brazilian semi-arid region. The data used were extracted from the literature, based on forage production. For the energy evaluation, the energy balance was performed and the energy efficiency, energy productivity, specific energy, and net energy metrics were applied. The financial feasibility analysis used the Net Present Value (NPV) and Internal Rate of Return (IRR). The energy balance revealed that the SC cultivation is viable for biomass commercial-scale production, with an energy efficiency of 3.36, an energy productivity of 0.25 kg MJ−1, a specific energy of 13.5 MJ kg−1, and an energy balance of 127,348 MJ ha−1. For the economic aspect, considering an attractive minimum rate of return of 8%, production also proved to be viable, in a time horizon of three years. The Net Present Value and IRR metrics were USD 2196 and the IRR was 46%, respectively. The results found are important to encourage new investments in rural properties in the semi-arid region, and cultivation in new areas proved to be an efficient alternative from an energy and economic point of view, in addition to collaborating for the energy transition to sustainable sources and in the mitigation of regional environmental impacts

Potentialities and Impacts of Biomass Energy in the Brazilian Northeast Region

In Northeast Brazil, the use of biomass for energy generation is settled on traditional productive arrangements, such as a sugarcane production system in the humid Atlantic coastal area and firewood extraction from native tropical dry forests in the west. In parallel, substantial amounts of other biomass sources, such as residues from agricultural or urban processes, are still little used or wholly wasted, fudging the opportunity to generate new value chains based on these biomass sources. We hypothesize that using these non-traditional biomass sources to produce biofuels would significantly increase the regional bioenergy supply. In this context, this article discusses the potential for the production and use of biofuels and bioenergy in Northeast Brazil and its effects on regional development, which may be useful for both private actors and policymakers in the energy sector. The use of biomass sources for energy in the region is significant, reaching approximately 8.8 million tons of oil equivalent (toe) per year, emphasizing the already consolidated production of sugarcane and its derivatives. The use of all biomass resources in the Northeast region could supply around 4% of the Brazilian national electrical energy demand, with an environmental footprint of 0.055 tCO2eq per toe, which would contribute to reducing emissions from the Brazilian energy matrix generation. Regarding the spatial distribution of biomass sources, sugarcane prevails on the coast, firewood and livestock manure in the dryland area towards the west, and municipal solid waste is distributed throughout the region within urban areas. Different from what we expected, the potential energy recovery from municipal waste and animal manure would increase by only 17% the current bioenergy supply. In the future, since the majority of the region presents a semi-arid climate with limited rainfall, to increase the use of biomass as an energy source, there is a need to increase the supply of biomass sources with high efficiency in water use and good yields in drylands. For this, the cultivation and use of cacti and agave, for example, could contribute to making biorefineries viable in the region. Above all, public policies for harnessing bioenergy in NE Brazil must seek opportunities associated with the carbon/decarbonization economy, with studies being needed to assess the technical, economic, social, and environmental viability of future productive arrangements

Biomassas de partes aéreas em plantas da caatinga Aboveground biomass of caatinga plants

As biomassas de partes aéreas de nove espécies da caatinga foram determinadas e relacionadas com as medidas das plantas, cortando-se 30 plantas de cada espécie e separando-as em caule, galhos, ramos e folhas. As espécies foram divididas em dois grupos: seis espécies com plantas grandes e três com plantas menores. Cada grupo foi separado em classes de diâmetro do caule (DAP). As alturas totais (HT) dobraram (3,8 a 8,5 m) da classe de menor para a de maior diâmetro (<5 e 27,5-30 cm), as áreas de projeção das copas (APC) aumentaram 14 vezes (4,8 a 67,3 m²) e as biomassas (B) cresceram 113 vezes (4 a 454 kg). Os valores máximos foram menores que os de outras formações vegetais tropicais de locais mais úmidos. As proporções das biomassas das partes em relação à biomassa aérea total variaram menos que os valores absolutos, indicando que as plantas vão-se desenvolvendo de forma mais ou menos proporcional. Nas plantas a partir de 17,5 cm de DAP, cerca de 70% da biomassa era de caules e galhos maiores que 5 cm de diâmetro, 20% de galhos entre 1 e 5 cm, 5% de ramos <1 cm e 5% de folhas. A variável isolada que melhor estimou as biomassas das partes, nos dois grupos de espécies, foi o DAP, com equações de potência (B = a DAP b). Em algumas partes e grupo, HT e APC também foram significativamente correlacionas com as biomassas, embora com R² inferiores às equações com DAP. Combinando DAP e HT, melhorou-se ligeiramente o ajuste, mas não deve compensar o esforço de obter H no campo. Portanto, as biomassas das partes da planta podem ser estimadas a partir das medidas dos diâmetros do caule, um processo não destrutivo.<br>Biomass of aboveground parts of nine caatinga species were determined and related to plant measurements. Thirty plants of each species were collected and separated into stems, branches, twigs and leaves. The species were divided in two groups: six species of large plants and three species of smaller plants. Each group was divided into classes of stem diameter (DBH). Plant height (H) doubled (3.8 to 8.5 m) from the smallest-diameter class to the largest diameter (<5 and 27.5-30 cm), canopy projection areas (CPA) increased 14 times (4.8 to 67.3 m²) and biomass (B) increased 113 times (4 to 454 kg). The highest values are below those found in other tropical vegetation types in more humid sites. The ratio of biomass of separated plant parts to total aerial biomass varied less than their absolute values, indicating that plants develop in a relatively uniform way. Plants with DBH above 17.5 cm had about 70% of biomass consisting of stems and branches > 5 cm diameter, 20% of branches from 1 to 5 cm, 5% of twigs < 1 cm and 5% of leaves. DBH was the single variable that best predicted biomass of parts, in both species groups, according to a power equation (B = a DBH b). H and CPA were also significantly related to biomass for some parts and group, but with R² lower than DBH. Combining DBH and H improved estimation but not enough to justify the extra field effort in determining H. Therefore, plant part biomass can be estimated from measurements of stem diameter, in a non-destructive process