Implementation of sequential cropping into JULESvn5.2 land-surface model

Camilla Mathison,Andy Wiltshire,Andrew J Challinor,Sophie Moulin,Sébastien Garrigues,Chetan Deva,Pete Falloon,Karina Williams

doi:10.5194/gmd-14-437-2021

Abstract

Abstract. Land-surface models (LSMs) typically simulate a single crop per year in a field or location. However, actual cropping systems are characterized by a succession of distinct crop cycles that are sometimes interspersed with long periods of bare soil. Sequential cropping (also known as multiple or double cropping) is particularly common in tropical regions, where the crop seasons are largely dictated by the main wet season. In this paper, we implement sequential cropping in a branch of the Joint UK Land Environment Simulator (JULES) and demonstrate its use at sites in France and India. We simulate all the crops grown within a year in a field or location in a seamless way to understand how sequential cropping influences the surface fluxes of a land-surface model. We evaluate JULES with sequential cropping in Avignon, France, providing over 15 years of continuous flux observations (a point simulation). We apply JULES with sequential cropping to simulate the rice–wheat rotation in a regional 25 km resolution gridded simulation for the northern Indian states of Uttar Pradesh and Bihar and four single-grid-box simulations across these states, where each simulation is a 25 km grid box. The inclusion of a secondary crop in JULES using the sequential cropping method presented does not change the crop growth or development of the primary crop. During the secondary crop growing period, the carbon and energy fluxes for Avignon and India are modified; they are largely unchanged for the primary crop growing period. For India, the inclusion of a secondary crop using this sequential cropping method affects the available soil moisture in the top 1.0 m throughout the year, with larger fluctuations in sequential crops compared with single-crop simulations even outside the secondary crop growing period. JULES simulates sequential cropping in Avignon, the four India locations and the regional run, representing both crops within one growing season in each of the crop rotations presented. This development is a step forward in the ability of JULES to simulate crops in tropical regions where this cropping system is already prevalent. It also provides the opportunity to assess the potential for other regions to implement sequential cropping as an adaptation to climate change.

Highlights

Climate change is likely to impact all aspects of crop production, affecting plant growth, development and crop yield (Hatfield and Prueger, 2015) as well as cropping area and cropping intensity (Iizumi and Ramankutty, 2015)
Mathison et al.: Implementation of sequential cropping into JULESv5.2 land-surface model grown for food and those grown for bio-energy in order to mitigate climate change (Frieler et al, 2015)
Garrigues et al (2015a) demonstrate that the Interactions between the Soil, Biosphere and Atmosphere (ISBA) landsurface model (LSM) (Noilhan and Planton, 1989), ISBA-A-gs (Calvet et al, 1998), is able to represent a 12-year succession of arable Mediterranean crops for a site in Avignon, France (Garrigues et al, 2015a, b). This type of cropping system is not typically represented in Land-surface models (LSMs); this study showed that the implementation of crop successions in an LSM leads to a more accurate representation of cumulative evapotranspiration over the 12-year period

Summary

Introduction

Climate change is likely to impact all aspects of crop production, affecting plant growth, development and crop yield (Hatfield and Prueger, 2015) as well as cropping area and cropping intensity (Iizumi and Ramankutty, 2015). Petrie et al (2017) discuss how the use of sequential cropping systems may have made it possible for populations in some areas to adapt to large changes in monsoon rainfall between 2200 and 2100 BC These ancient agricultural practices are common today across most tropical countries but may be a useful adaptation in areas where traditionally mono-crop systems are used, in order to meet a future rising demand for food (Hudson, 2009) or the demand for bio-fuels. This sort of adaptation is already happening in some locations. Warmer spring temperatures in the Brahmaputra catchment have allowed earlier planting of a winter crop, leaving time for a second crop (Zhang et al, 2013)

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