The Solar Corridor Crop System

Implementation and Impacts

C. LeRoy Deichman, Robert J. Kremer

• Publisher: Academic Press
• Year: 2019
• ISBN:
  9780128147931
• Topic: Technology & Engineering
• Subtopic: Agriculture
• Index: Technology & Engineering

The Solar Corridor Crop System: Implementation and Impacts presents a case-study format on the planning and implementation of alternative cropping systems designed to maximize incident sunlight and bio-support of all crops in a rotation system. The book describes the basic component of the system, an increased access point of incident sunlight between each row or pairs of rows that enables a more uniform vertical distribution of incident sunlight to chloroplasts within the entire corn leaf canopy. While the production environment and environment specific genetics determine the performance potential of this principle, by maximizing the principles that light is basic to crop yield, a solar corridor ultimately contributes to increased grain yield.

Written by experts who were integral in the development of solar corridor systems, and providing real-world examples of the methods, challenges and future prospects, this book will be valuable for those seeking to increase yield-per-acre through both primary and cover-crops.

• Introduces readers to the concept of alternative row-cropping and its implementation
• Presents real-world experience, including challenges and solutions
• Encourages research in maximizing photosynthesis impact on crop yield

Chapter 1

Photosynthesis in the solar corridor system

Jerry L. Hatfield and Christian Dold, National Laboratory for Agriculture and the Environment, Ames, IA, United States

Abstract

Photosynthesis is the conversion of light into carbohydrates at the cellular level. Photosynthetic rates are determined by the availability of light, carbon dioxide (CO₂), and water for a given temperature regime. There are differences between plant species as classified into C₄ and C₃ plants, especially in their response to light and CO₂. Photosynthesis occurs at the leaf level; however, the overall photosynthetic rate at the unit area level is dependent on the rate of leaf area accumulation by plants and the arrangement of leaves into canopies. Leaf level photosynthesis is affected by the temperature of the leaf and the water and nutrient status that determines the efficiency of the photosynthetic process. At the canopy level, the leaf arrangement becomes the important factor that determines how light is distributed within the canopy, especially diffuse light distribution, and equally important is the effect of the canopy architecture on the movement of CO₂ into the canopy to prevent this from becoming a limiting factor. Canopy architecture is a function of row spacing, plant population, crop species, and mixtures of plants, and radiation use efficiency becomes the critical metric of how canopy architecture integrates multiple factors into a quantitative assessment of cropping systems. Photosynthesis is critical to converting light into carbohydrates, and understanding the limitations of this process will guide us in manipulating the leaf and canopy leaf processes to achieve future productivity gains.

Keywords

Light interception; radiation use efficiency; canopy architecture; canopy arrangement; crop stress

Contents

• Introduction 1
• Radiation use efficiency 4
• Photosynthesis in response to environmental factors 10
  • Carbon dioxide response 11
  • Temperature 14
  • Water 15
  • Nutrients 15
• Plant canopies affect light distribution and photosynthesis 16
  • Leaf area 16
  • Canopy architecture 17
  • Phenological stages 19
  • Plant arrangement into canopies 19
  • Increasing plant productivity 23
• Conclusion 24
• References 25
• Further reading 33

Introduction

Photosynthesis is the capture of light within the chloroplast that combines carbon dioxide (CO₂) with water (H₂O) to create a simple sugar (C₆H₁₂O₆) and can be expressed as

$\left[6{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}\right]\mathrm{light}={\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2$ (1.1)

(1.1)

However, this simple process is made complex by the factors that affect the availability of sunlight onto the leaves in a plant canopy. This can be envisioned through the light response curve diagram, which depicts how available sunlight (irradiance) is related to the rate of photosynthesis (Fig. 1.1). Important features in this diagram include the saturation point where there is no further change in photosynthetic rate with additional light, the compensation point where this amount of photosynthesis offsets the respiration rate, and the photosynthetic efficiency (or quantum yield) which is the rate of increase in photosynthesis per unit of light in the linear phase before saturation is reached. These principles of photosynthesis are known in basic plant physiology and determine the effectiveness of light capture within a plant canopy and the amount of photosynthesis generated (Marshall and Biscoe, 1980; Evans et al., 1993).

Figure 1.1 Generalized photosynthesis response to available photosynthetically active radiation showing light saturation level.

As described in Fig. 1.1, both the amount of incident radiation (1) and the efficiency of the plant to produce photosynthates (2) determine crop production as related to photosynthesis. Photosynthetic efficiency differs among plants with C₃, C₄, and crassulacean acid metabolism (CAM) pathway of carboxylation, and may be limited or enhanced by (un)favorable environmental factors, such as temperature (e.g., Ehleringer and Pearcy, 1983; Yamori et al., 2014), water (e.g., Chaves et al., 2002; Flexas et al., 2006; Ghannoum, 2009), ambient CO₂ concentration (e.g., Farquhar et al., 1980; Von Caemmerer and Furbank, 1999; Leakey et al., 2004; Ainsworth and Long, 2005; Sharkey et al., 2007), nutrients (e.g., Arnon, 1956; Huber, 1985; Sinclair and Horie, 1989; Abadía, 1992; Evans, 1996; Balakrishnan et al., 2000; Cakmak and Kirkby, 2008; Gu et al., 2017), and interactions among them, which eventually impact crop production.

Solar radiation is the sole source of energy for field crops to produce photosynthates, and light interception is often a limiting factor for crop production. For example, solar brightening (i.e., the decadal increase of incident solar radiation) has reportedly increased maize yields in the US Corn Belt, while solar dimming (i.e., the opposite effect) may have affected maize production in Northeast China (Tollenaar et al., 2017; Zhao et al., 2015). What becomes important in canopy level photosynthesis is the amount of light transmitted to each leaf within the plant canopy. This principle was first described by Monsi and Saeki (1953) where they applied the Beer–Bouguer–Lambert law to plant canopies as

$I=I_o{\mathit{exp}}^{-k\mathrm{LAI}}$ (1.2)

(1.2)

where I is the light intensity at any point in the canopy, I_o is the light at the top of the canopy, k is an extinction coefficient, and LAI is the leaf area index of the canopy above the level where I is estimated. Eq. (1.2) states that I decreases exponentially in plant canopies with increasing LAI and the angular arrangement of the leaves, expressed as the extinction coefficient (k). Note that Eq. (1.2) applies to random plant canopy structures with uniform radiation distribution at any canopy level. This is violated in field crops, where plant canopies are arranged in rows and leaves are clumped. In that case,...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Foreword
• Preface
• Introduction
• Chapter 1. Photosynthesis in the solar corridor system
• Chapter 2. Variety selection for the solar corridor crop system (SCCS)
• Chapter 3. Maize water use and yield in the solar corridor system: a simulation study
• Chapter 4. Soil health benefits of the solar corridor crop system
• Chapter 5. Putting it all together
• Chapter 6. The economic and social conditions of the solar corridor cropping system
• Chapter 7. The solar corridor crop system: a pivotal production system for African smallholder farmers
• Chapter 8. Vision
• Index