Incubation methods for assessing mineralizable nitrogen in soils under sugarcane

Abstract

SUMMARYConsidering nitrogen mineralization (N) of soil organic matter is a key aspect for the efficient management of N fertilizers in agricultural systems. Long-term aerobic incubation is the standard technique for calibrating the chemical extraction methods used to estimate the potentially mineralizable N in soil. However, the technique is laborious, expensive and time-consuming. In this context, the aims of this study were to determine the amount of soil mineralizable N in the 0-60 cm layer and to evaluate the use of short-term anaerobic incubation instead of longterm aerobic incubation for the estimation of net N mineralization rates in soils under sugarcane. Five soils from areas without previous N fertilization were used in the layers 0-20, 20-40 and 40-60 cm. Soil samples were aerobically incubated at 35 °C for 32 weeks or anaerobically incubated (waterlogged) at 40 °C for seven days to determine the net soil N mineralization. The sand, silt and clay contents were highly correlated with the indexes used for predicting mineralizable N. The 0-40 cm layer was the best sampling depth for the estimation of soil mineralizable N, while in the 40-60 cm layer net N mineralization was low in both incubation procedures. Anaerobic incubation provided reliable estimates of mineralizable N in the soil that correlated well with the indexes obtained using aerobic incubation. The inclusion of the pre-existing NH 4 + -N content improved the reliability of the estimate of mineralizable N obtained using anaerobic incubation.Index terms: Saccharum spp., net N mineralization, aerobic incubation, anaerobic incubation.(

Blending polymer-sulfur coated and NBPT-treated urea to improve nitrogen use efficiency and grain yield in corn production systems

“…The dry weight of straw left in the soil surface was 16.5 Mg ha -1 at Site 3 and 18 Mg ha -1 at Site 4, which is in agreement with the numbers reported in the literature (Trivelin et al, 2013;Vieira-Megda et al, 2015;Leite et al, 2016;. Sugarcane straw presents a high C:N ratio of 100:1 (Fortes et al, 2012), which results in high N immobilization rates (Mariano et al, 2013), due to increased microbiological activity caused by the energy input into the soil, which is considered to be the main reason behind the low NUE values in sugarcane cropping systems.…”

Predicting Economic Optimal Nitrogen Rate with the Anaerobic Potentially Mineralizable Nitrogen Test

“…Soil texture can influence N mineralization and the ability of PMN an to relate to EONR (Bushong et al, 2007; Mariano et al, 2013; Six et al, 2002). For example, clay particles can form aggregates with organic matter that protect it from mineralization (Bloem et al, 1994; Kuzyakova et al, 2006; Shen et al, 1989), and NH 4 + produced during PMN an analysis can be fixed by clay particles that are abundant in fine‐textured soils (Russell et al, 2006).…”

Misturas de ureia revestida com polímeros e ureia convencional na adubação da cultura de milho

“…A maior fonte de N para as plantas é o solo e não aquele aplicado como fertilizante (FRANCO et al, 2011;MARIANO et al, 2013). A maior parte do N do solo está na forma orgânica (aproximadamente 90%), enquanto que o N inorgânico ou N mineral representa geralmente menos do 10% do N total presente no solo (STEVENSON, 1982 FAURIE, 1990;CANTARELLA, 2007).…”