IRRIGAÇÃO POR GOTEJAMENTO SUBSUPERFICIAL EM CULTIVARES DE CANA-DE-AÇÚCAR IMPACTAM A AGREGAÇÃO DO SOLO?

IRRIGAÇÃO POR GOTEJAMENTO SUBSUPERFICIAL EM CULTIVARES DE CANA-DE-AÇÚCAR IMPACTAM A AGREGAÇÃO DO SOLO? YASMIN REIS MAGALHÃES1; ANDERSON PRATES COELHO2; CAROLINA FERNANDES1; ALEXANDRE BARCELLOS DALRI2 1 Departamento de Ciências da Produção Agrícola, Universidade Estadual Paulista (Unesp), Faculdade de Ciências Agrárias e Veterinárias, Via de Acesso Professor Paulo Donato Castellane, s/n Km 5, 14884-900, Jaboticabal, São Paulo, Brasil. [email protected]; [email protected] 2 Departamento de Engenharia e Ciências Exatas, Universidade Estadual Paulista (Unesp), Faculdade de Ciências Agrárias e Veterinárias, Via de Acesso Professor Paulo Donato Castellane, s/n Km 5, 14884-900, Jaboticabal, São Paulo, Brasil. [email protected]; [email protected] 1 RESUMO Objetivou-se avaliar o efeito da irrigação por gotejamento subsuperficial em cultivares de cana-de-açúcar, contrastantes na responsividade à irrigação, na agregação de Latossolo argiloso. O experimento foi realizado em Latossolo Vermelho eutroférrico, de textura argilosa (587 g kg-1 de argila). Foram coletadas amostras deformadas de solo em vinte pontos em cada uma das quatro áreas de cana-de-açúcar avaliadas nas camadas 0,00-0,10 m e 0,10-0,20 m. As áreas correspondiam ao cultivo irrigado e não irrigado, das cultivares CTC 4 e IACSP93-3046. Foram determinados e calculados o índice de estabilidade dos agregados, diâmetro médio ponderado de agregados, fracionamento físico do carbono orgânico e as classes de agregados. Os dados foram submetidos à estatística descritiva e multivariada de fatores. De acordo com as correlações das variáveis, a agregação do solo foi dividida em dois processos, sendo o primeiro denominado de “Dimensão de agregados” e o segundo “Estabilidade de agregados”. Observou-se que a irrigação por gotejamento subsuperficial promove maior “Estabilidade de agregados” do solo em áreas cultivadas com cana-de-açúcar. Além disso, cultivares de cana-de-açúcar proporcionam diferenças na agregação do solo, sendo que a cultivar responsiva à irrigação IACSP93-3046 promove maior “Dimensão de agregados” do solo em relação a cultivar não responsiva CTC 4. Palavras-chave: diâmetro médio ponderado de agregados, estabilidade de agregados, carbono orgânico, Latossolo. MAGALHÃES, Y. R.; COELHO, A. P.; FERNANDES, C.; DALRI, A. B. DOES SUBSURFACE DRIP IRRIGATION IN SUGARCANE CULTIVARS IMPACT SOIL AGGREGATION? 2 ABSTRACT The aim was to evaluate the effect of subsurface drip irrigation with sugarcane cultivars, contrasting in the responsiveness to irrigation, in the aggregation of Oxisol clayey. The experiment was conducted in a clayey Oxisol (587g kg-1 of clay). Deformed soil samples were collected at twenty points in each four areas of sugarcane evaluated in the layers 0.00-0.10 m and 0.10-0.20 m. The areas corresponded to the irrigated and non-irrigated cultivation of cultivars CTC 4 and IACSP93-3046. The aggregate stability index, weighted average diameter of aggregates, physical fractionation of organic carbon and aggregate classes were determined and calculated. The data were submitted to the descriptive and multivariate factor statistics. According to the correlations of the variables, soil aggregation was divided into two processes, the first being called “Aggregates dimension” and the second “Aggregates stability.” It was observed that subsurface drip irrigation promotes greater soil “Aggregate stability” in areas cultivated with sugarcane. Additionally, sugarcane cultivars provide differences in soil aggregation, and the cultivar responsive to irrigation IACSP93-3046 promotes a larger soil “Aggregates dimension” than the non-responsive cultivar CTC 4. Keywords: weighted average diameter of aggregates, aggregate stability, organic carbon, Oxisol.

Soil Quality Indicators in Conventional and Conservation Tillage Systems in the Brazilian Cerrado

Conventional and conservation tillage systems can alter soil aggregation and total and labile soil organic matter (SOM) contents. This study aimed to determine the degree of soil aggregation, quantify total carbon (TC), permanganate oxidizable carbon (POXC), light organic matter (LOM), and potentially mineralizable carbon (CO2-C) contents in soils aggregates, and assess soil quality indices at sites under conventional and conservation tillage in the Cerrado region of Minas Gerais State, Brazil. Four experimental areas were analyzed: a area under conventional tillage for 20 years, a area under no-till for 6 years, a area under no-till for 18 years, and a reference area of undisturbed Cerrado vegetation. Soil aggregates retained on 8.0 to 4.0 mm sieves were evaluated for size class distribution and mean weight diameter. TC, POXC, LOM, daily and total CO2-C emissions were also analyzed. These data were used to calculate the C/N ratio and sensitivity, carbon pool, and lability indices. The results of SOM compartments were in agreement with those obtained for the soil aggregation status. Environmental conditions at no-till areas promoted macroaggregate formation and preserved TC and LOM contents, resulting in a high degree of aggregate stability. Soil quality indices were sensitive to identify changes between the reference area and managed areas. Soil aggregates from no-till areas had higher CO2-C emissions and accumulations than those from the conventional tillage area.