Influence of urea fertilization and urease inhibitor on the size and activity of the soil microbial biomass under conventional and zero tillage at two sites

Abstract

Fertilizers are frequently used in agriculture to enhance crop yield and quality. Increasingly, microbial and enzyme inhibitors are being used to enhance the efficiency of fertilizer nitrogen use. The assumption being made is that the impact of these compounds is short-term or localized and thus does not adversely impact soil quality. This study investigates the implications of urea fertilizer with and without urease inhibitor [N-(n-butyl) thiophosphoric triamide, NBPT], conventional and zero tillage systems, and soil types on the soil biological characteristics including N mineralization. Microplot studies were conducted in clay loam and fine sandy loam soils in Manitoba. Soil type had a significant effect on the soil organic C but tillage did not have any significant effect. Soil microbial biomass C content ranged widely (131–1215 µg g−1 soil). The clay loam soil generally tended to contain higher biomass C than the sandy loam soil. The potential soil mineral N production (N0) was higher in clay loam soil (92.6 µg g−1 soil) than sandy loam soil (40.2 µg g−1 soil). Tillage systems, urea and urease inhibitor application had no significant impact on the soil biomass C, N0, arylsulfatase or acid and alkaline phosphatase content. At these sites considerable fluctuations occurred in the microbial and biochemical properties due to the variation of soil type. In general, these fluctuations were mainly related to soil organic matter and soil moisture content. Tillage system, urea with and without NBPT application did not contribute any notable impact on the soil biological properties reported in this study. Key words: Soil biological quality, soil type, urease inhibitor, conventional tillage, zero tillage

Conservation Tillage, Rotations, and Cover Crop Affecting Soil Quality in the Tennessee Valley: Particulate Organic Matter, Organic Matter, and Microbial Biomass

“…The decrease in soil microbial biomass C by depth is more pronounced between the first and second layer, especially under no tillage, probably because of surface deposition of crop residue and shallow root growth. The depth variation in microbial biomass could be associated with C stratification because others have found a strong link between them (Carter 1986;Doran 1987;Banerjee, Burton, and Grant 1999). Results confirmed a strong relationship between SOC and microbial biomass C with a correlation coefficient of 0.86 over all treatments and depths (data not shown).…”

“…Anderson and Domsch (1989) suggest that a more diversified microorganism community and larger population are expected under polyculture systems. Furthermore, long-term monocropping under intensive tillage depleted soil organic matter, which could be favorable to rapid organic matter accumulation and increases in soil microbial biomass C. Another factor that could also contribute to a large increase in soil microbial biomass was the clayey soil texture, which also provides favorable conditions for SOC improvement and consequent increased soil microbial biomass (Powlson and Brookes 1987;Banerjee, Burton, and Grant 1999).…”

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

“…An earlier study concluded that the addition of urea alone or urea with NBPT did not affect the biological properties (microbial biomass C?N content and content of arylsulfarase, acid phosphatase and alkaline phosphatase) of the test soil over a period of 1 year and 8 months (Banerjee et al 1999). Further studies of both the long-and short-term effects of NBPT (and other urease inhibitors) on crops/plants and the soil microbiome are obviously still needed.…”

Economic and Soil Environmental Benefits of Using Controlled‐Release Bulk Blending Urea in the North China Plain

“…Soil microbial communities are involved in many important soil biological processes like organic matter degradation, nutrient cycling, and ecosystem function (Lupwayi et al, 2017). At low dosages (such as 50 kg N ha À1 ), N fertilization did not affect soil microbial biomass carbon and activities (Banerjee et al, 1999). At higher N dosages (like 400 kg N ha À1 ), the functional diversity of soil bacteria decreased (Sarathchandra et al, 2001).…”