Abstract
ABSTRACT The application of nitrogen fertilizers, both organic and mineral, can cause nitrate losses by leaching. To minimize this effect, enzyme inhibitors are used. However, the effects on microbial biomass, which is the most sensitive and dynamic compartment of nutrients in the soil, as well as its effect on nutrients such as phosphorus (P) are unknown. This study aimed to evaluate the influence of the enzyme inhibitor (EI) on soil microbial phosphorus (Pm) when mineral fertilizer (NPK) or liquid swine manure (LSM) was applied in corn cultivation. The experiment was installed in a Humic Cambisol in Lages – SC, Brazil (27° 47’ 08” S; 50° 18’ 09” W) in the 2012/2013 season. The treatments consisted of: i) NPK; ii) NPK + EI; iii) LSM; iv) LSM + EI, applied before sowing of corn, and v) control (without application of fertilizer and enzyme inhibitor) arranged in a randomized block design, under no-tillage system. Soil samples were collected from the 0-0.10 m layer at 0, 10, 25, 58, 90, 135 and 202 days after application of the treatments. The Pm content was not affected by the enzyme inhibitor application but was influenced throughout the crop cycle in response to water balance and corn cultivation.
Highlights
In an attempt to reduce nitrogen (N) losses through ammonia volatilization and nitrate leaching, the use of enzyme inhibitors (EI) such as N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiamide (DCD) has been shown to be viable (Zaman et al, 2009; Dall'Orsoletta et al, 2017)
Pm contents did not differ between treatments, except at 202 days after application of treatments (DAA) (Table 1), when the values observed in treatments that received fertilization were higher than those in the control
The available P extracted by anion exchange resin (P-AER) was not affected by the interaction between sources and sampling periods, only by the factors individually
Summary
In an attempt to reduce nitrogen (N) losses through ammonia volatilization and nitrate leaching, the use of enzyme inhibitors (EI) such as N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiamide (DCD) has been shown to be viable (Zaman et al, 2009; Dall'Orsoletta et al, 2017). Organic fertilization adds to the soil, besides macroand micronutrients that are essential for plant development (Lourenzi et al, 2013), carbonic compounds which act as stimulants of microbial activity (Bünemann et al, 2004; Singh et al, 2016). Soil microbial biomass is responsible for the mineralization of organic compounds, being directly involved in geochemical cycles of C, N and P (Cleveland & Liptzin, 2007; Turner et al, 2013; Singh et al, 2016), but is affected by abiotic factors such as temperature, humidity and availability of nutrients (Gatiboni et al, 2008; Bünemann et al, 2013; Turner et al, 2013). Concomitant use of both inhibitors (DCD and NBPT), since they maintain N in less available forms, can be limiting to soil microorganisms (Mooshammer et al, 2014)
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