Nitrogen Mineralization as Affected by Temperature in Calcareous Soils Receiving Repeated Applications of Dairy Manure

Abstract

Core Ideas Prediction of N mineralization is dependent on accurate rate correction factors and the ratio of the change of the rate coefficient of mineralization for every increase in temperature of 10°C (Q10) based on temperatures observed in the region. Few studies have investigated N mineralization in soils receiving repeated applications of manures at low temperatures. This study determined that manure additions may lead to larger Q10 values at low temperatures and growing degree‐days may aid in predicting N release from these soils. There are currently no tools available to help predict N mineralization for the silty soils found in southern Idaho receiving repeated manure applications. This experiment aimed to determine the effect of temperature on N mineralization from control and manured soils, develop N mineralization rate correction factors for temperature [ratio of the change in the rate coefficient of mineralization for every 10°C increase (Q10) and temperature factors], and create a simple model for predicting N mineralization as a function of growing degree‐days. Manured and control soils underwent a 49‐d laboratory incubation at five temperatures (–14, 4, 10, 23, and 30°C); soil inorganic N concentration was determined at 0, 1, 3, 5, 7, 13, 20, 28, 35, 42, and 49 d. Net N mineralization was fitted to a zero‐order model, where the rate coefficient (k) values for the manured soil ranged from 0.017 to 1.28 mg kg–1 soil d–1 over the five temperature treatments, whereas k in the control measured 0.028 to 0.53 mg kg–1 soil d–1. The calculated Q10 values from –14 to 30°C were 2.7 and 2.0 for the manured and control soils respectively. At low temperatures (–14 to 4°C), the Q10 for manured soil was 5.1 compared with 1.5 for the control. This suggests that manure additions may lower the temperature threshold for N mineralization under near frozen soil conditions. Manure treatment effects on the temperature factor were not observed, suggesting that manure application history may not need to be considered when developing temperature factor coefficients for N mineralization models.