Soil respiration in relation to cropping sequence, nutrient management and environmental variables

Abstract

ABSTRACT Soil respiration (Rs) measurements in relation to agricultural management and environmental variables are necessary to improve our understanding of net ecosystem carbon balance (NECB) and to predict soil’s feedback to climate change. The objectives of this study were to analyze the seasonal dynamics of Rs in maize-wheat and cotton-wheat crop rotations and to quantify the effects of temperature, moisture and management on Rs, and NECB. Rs was measured in situ by open chambers over 2 years. In-season Rs varied with crop growth and peak rates coincided with the maximum growth stage of a crop. Rs rate was higher in maize than in cotton. Mean Rs in winter wheat was about one-third of that in preceding maize or cotton. Root respiration comprised 13–29% of Rs in different crops. The NECB suggested that soil could be losing organic C at 381–643 g C m−2 y−1. Application of organic amendments along with inorganic fertilizers improved NECB underpinning their role in converting a cropping sequence from potential source to sink of carbon. Temperature sensitivity of Rs was strongly modulated by soil moisture suggesting that increased Rs due to warming coupled with high moisture could provide a positive feedback to climate change.