Effects of Organic and Conventional Management of Sugar Cane Crop on Soil Physicochemical Characteristics and Phosphomonoesterase Activity Luiza L. A. Purcena,* ,† Maria Carolina B. Di Medeiros, † Wilson M. Leandro, ‡ and Ka ́ tia F. Fernandes † † Departamento de Bioquı ́ mica e Biologia Molecular, ICB II, e ‡ Escola de Agronomia e Engenharia de Alimentos, Universidade Federal de Goia ́ s, Samambaia Goiâ nia, Brazil ABSTRACT: Soil enzymes play an important role in agriculture and particularly in nutrient cycling. They are also involved in the degradation, transformation, and mineralization of organic matter and availability of nutrients in soil. It is believed that organic agriculture causes fewer losses to soil quality and is less aggressive to the environment than conventional management. In this study, the effects of conventional (CM) and organic management (OM) on phosphomonoesterases, an important enzyme for soil fertility, were evaluated and compared to those results from native Cerrado (Brazilian Savanna) soil (NS), because they are the most common phosphatases in soils. The results showed that there were both acid (AcP) and alkaline (AkP) phosphatases in all soils tested and that AcP activity was higher than that of AkP. In contrast to AkP, AcP had its activity affected by land use. In the cultivated areas there was a reduction of almost 50% of AcP activity respect to native unexploited soils and there was no significant difference between organic and CM, demonstrating that independent of the management chosen, there was an impact of land use on AcP activity. Principal component analysis indicated that characteristics related to pH such as alkali saturation (V%), aluminum saturation (M%), Al 3+ , soil total acidity (H+Al), and Ca 2+ are the main factors that permit distinguishing NS from OM and CM. KEYWORDS: phosphomonoesterases, Cerrado, soil, principal component analysis, management ■ INTRODUCTION Soil is a complex ecosystem in which the combination of insects, nematodes, annelids vegetation, microorganisms, and anthropogenic modifications will determine its characteristics. Management of agricultural systems also contributes to soil characteristics and can affect soil quality in the long term by modifying soil physical, chemical, and biological characteristics at a rate that is largely dependent on climate conditions and farming practice. 1 Cerrado, also known as the Brazilian Savanna, soils are acid and have low availability of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), molybdenum (Mo), and zinc (Zn). They are high in aluminum (Al) saturation and possess high P fixation capacities. 2 In addition, Cerrado soils present crop production limitations: 5-6 month dry season; dry spells of 1-3 weeks during the rainy season, generally associated with high evapotranspiration rates; low water-holding capacity, even in clayey soils; limited rooting depth of many crops as a function of aluminum toxicity and/or calcium deficiency in subsurface soil layers. 3 Despite all of these problems, a breakthrough in agricultural development has taken place in the area during recent decades, mainly involving food crops, pasture, and coffee. Yield levels of some of these crops exceed national averages. 3 The overexploitation of soil is a consequence of the current needs to sustain the high demand for food and the search for alternative fuel sources such as ethanol. The ethanol produced from sugar cane monoculture has become very important worldwide, because it is a viable alternative to vehicle fossil fuels, 4 especially considering the increasing prices of oil as a consequence of the risk of shortage. Additionally, in contrast to oil, ethanol is a renewable energy source and reduces the greenhouse effect of gas emissions. Moreover, gas emission produced from sugar cane ethanol is much less aggressive than that from corn because it decreases the use of fossil fuels by using biomass. 4 Several authors have reported that monoculture planting causes the loss of soil fertility because of the nutrients consumed by plants and pesticide use. 5-7 Then, in an attempt to lessen agricultural impacts of monocultures, several manage- ments have been proposed, including organic management (OM), in which only organic fertilizers are used and there is no use of pesticides or synthetic fertilizers. Some papers have already described the benefits of OM 1,8 by preserving some biochemical characteristics such as the global, organic, and basal carbon (C). Nevertheless, the impact of this management on soil enzymes has not been evaluated yet. Biomass and enzymes present in soil are responsible for several chemical reactions such as nutrient cycling and the physicochemical characteristics of this environment. 9 The activities of enzymes in soil have been correlated with plant growth and are reported as a useful tool to measure soil fertility, 10,11 making them great candidates to measure soil quality. In addition, enzymes are sensitive to environmental changes and are more effective than microorganisms as Received: July 22, 2013 Revised: January 21, 2014 Accepted: January 29, 2014 Published: January 29, 2014 Article pubs.acs.org/JAFC © 2014 American Chemical Society 1456 dx.doi.org/10.1021/jf403141w | J. Agric. Food Chem. 2014, 62, 1456-1463