A simple model for estimation of above and below ground carbon in cereal crops

Carbon (C) is an essential part of healthy soil. Healthy soils play an important role in improving the life of all living organisms on earth (plants, humans, animals, birds, insects, microbes etc.). Best agronomic practices for field crop production sequester more carbon (due to higher photosynthesis) below and above the ground that makes the soils healthy and sustainable. Healthy soils increase yield per unit area and so reduce the problem of food insecurity. Higher photosynthetic efficiency (higher CO2 uptake by the plants) reduces the problem of global warming and climate change. According to an estimate, plants capture about 860 gigatons of CO2 each year from the atmosphere, storing it in their shoots, and roots (1 kg of carbon is equal to 3.67 kg of CO2). The aim of this study was to develop a simple calculation (model) for researchers to easily estimate the carbon content (CC) capture by plants in below (roots) and above ground (shoots) parts. Considerable variation in total CC (TCC) accumulation and its partitioning into above ground parts (ACC) and below ground parts (BCC) exists which depends on crop species and genotypes, crop nutrition, crop competitions and intercropping, fertilizers application, irrigation, tillage, biotic and abiotic stresses, soil types and environment etc. The CC estimation is explained in detail with four examples on major cereal crops (wheat, rice, maize and barley) for the world leading countries in 2018−2019. In the first example using wheat, the TCC estimated for wheat crop in Pakistan was 37.4 metric tons (MT) of which 30.5 MT was allocated into ACC (shoots) and 6.9 MT into BCC (roots). The highest value of TCC accumulation for wheat crop was estimated for the European Union which was 216.3 MT (176.4 ACC + 39.9 BCC). In the second example using rice crop, TCC for the world leading countries was estimated and the leading country was China with TCC of 161.7 MT (131.9 ACC + 29.8 BCC). Example three is about the CC estimation for maize crop, and the leading country was USA having the highest TCC value of 505.3 MT (ACC = 412.1 MT, BCC = 93.2 MT). The Russian Federation ranked first for barley crop and the highest TCC value of 29.2 MT was recorded (23.8 MT ACC + 5.4 MT BCC). It was confirmed while using this model that out of the 100% (TCC) fixed, about 82% CC is partitioned into above ground parts (ACC) and the remaining 18% CC is allocated into below ground parts (BCC). Due to this model, we can easily calculate the TCC accumulation and its partitioning into ACC and BCC per unit area (kg·ha−1). For example, the TCC was easily calculated for the 40 world leading countries for wheat, rice, maize and barley during 2019. The results revealed that the TCC ranged from 4,414 to 13,243 kg·ha−1 for wheat, 4,578 to 11,444 kg·ha−1 for rice, 5,150 to 15,450 kg·ha−1 for maize, and 3,443 to 13,733 kg·ha−1 for barley among the top 40 countries. This is the most simplified approach for estimating carbon content in the below-ground (roots) and above-ground (shoots) parts of field crops.