Soil and Fertilizers

Managing the Environmental Footprint

Rattan Lal, Rattan Lal

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9780429895548
• Edition: 1
• Topic: Ciencias biológicas
• Subtopic: Conservación y Protección del Medio Ambiente

Soil and Fertilizers: Managing the Environmental Footprint presents strategies to improve soil health by reducing the rate of fertilizer input while maintaining high agronomic yields.

It is estimated that fertilizer use supported nearly half of global births in 2008. In a context of potential food insecurity exacerbated by population growth and climate change, the importance of fertilizers in sustaining the agronomic production is clear. However, excessive use of chemical fertilizers poses serious risks both to the environment and to human health.

Highlighting a tenfold increase in global fertilizer consumption between 2002 and 2016, the book explains the effects on the quality of soil, water, air and biota from overuse of chemical fertilizers. Written by an interdisciplinary author team, this book presents methods for enhancing the efficiency of fertilizer use and outlines agricultural practices that can reduce the environmental footprint.

Features:

• 
  
  

• Includes a thorough literature review on the agronomic and environmental impact of fertilizer, from degradation of ecosystems to the eutrophication of drinking water

• 
  
  

• Devotes specific chapters to enhancing the use efficiency and effectiveness of the fertilizers through improved formulations, time and mode of application, and the use of precision farming technology

• 
  
  

• Reveals geographic variation in fertilizer consumption volume by presenting case studies for specific countries and regions, including India and Africa

• 
  
  

• Discusses the pros and cons of organic vs. chemical fertilizers, innovative technologies including nuclear energy, and the U.N.'s Sustainable Development Goals

Part of the Advances in Soil Sciences series, this solutions-focused volume will appeal to soil scientists, environmental scientists and agricultural engineers.

1	Effects of Fertilizers on Soil Quality and Functionality Rattan Lal

CONTENTS

1.1 Introduction

1.1.1 Global Fertilizer Use

1.1.2 The Soil-Water-Air-Quality Nexus

1.1.3 Objectives and Expected Output

1.2 Global Food Demand

1.2.1 Trends in Food Grain Production

1.3 Fertilizer Use and Crop Response

1.3.1 Adverse Impacts on Soil, Water, and Air

1.3.2 Soil Biodiversity and Enzymes

1.3.3 Effects on Soil Enzyme

1.3.4 Soil Physical Properties

1.3.5 Soil Organic Carbon Concentration

1.3.6 Productivity Effects of Organic versus Inorganic Fertilizers

1.4 Holistic Management to Reduce the Input of Chemical Fertilizers

References

1.1 INTRODUCTION

1.1.1 GLOBAL FERTILIZER USE

Global fertilizer supply has increased drastically since 1960. The present global fertilizer supply (N + P₂O₅ + K₂O, 10⁶ Mg) for 2015–2020 (Table 1.1) indicates an increasing trend of 1.46%/yr over the six-year period. However, the rate of increase in global fertilizer consumption was 5.5%/yr between 1960 and 1990 and 2.9%/yr between 1990 and 2020. Among all fertilizers, the annual rate of growth of N was 7.1% between 1960 and 1990, compared with 4.4% between 1990 and 2020 (Table 1.2). The annual rate of fertilizer growth between 1990 and 2020 has been especially high for Asia (i.e., China and India) but has lagged behind in sub-Saharan Africa (SSA).Thus, the agronomic yield of crops in SSA has also stagnated, and the small rate of growth in some regions is much lower than its technical potential (Lal 2017). While the growth rate and the total global consumption of fertilizers have increased, the use efficiency of fertilizer has remained low, especially that of the nitrogenous (N) fertilizer. In developing countries and also in emerging economies (i.e., India and China), the use efficiency of N fertilizers can be as low as 30%. Therefore, a large proportion of the reactive N is leaked into the environment (water and air) with dire consequences.

TABLE 1.1
Total Global Grain Production from 2008–2009 to 2018–2019

Year	World Population (Billions)	Total Grain Production (Million Tons)	Per Capita Grain Production (Kg)
2008/09	6.789	2241.6	330
2009/10	6.872	2241.5	332
2010/11	6.957	2200.4	316
2011/12	7.041	2314.4	328
2012/13	7.126	2266.2	318
2013/14	7.211	2474.7	367
2014/15	7.295	2532.0	347
2015/16	7.380	2058.0	278
2016/17	7.464	2186.0	292
2017/18	7.547	2142.0	283
2018/19	7.631	2120.0	277
2019/20	7.713
2020/21	7.795

Source: FAO (2017a) and UN (2019).

TABLE 1.2
World’s Fertilizer Use from 1960 to 2020

Fertilizer	Fertilizer Use (10^6 Mg/yr)				Annual Growth (%)
	1959/60	1989/90	2018	2020	1960–1990	1990–2020
Nitrogen	9.5	79.2	169.0	170.8	7.1	4.4
Phosphorus	9.7	37.5	51.2	53.1	4.5	1.1
Potash	8.1	26.9	47.2	49.5	4.0	1.2
Total	27.4	143.6	267.4	273.4	5.5	2.9

Source: Adapted and recalculated from Bumb and Baanante (1996, Columns 2, 3, and 6) and FAO (2017b, Columns 4, 5, and 6).

1.1.2 THE SOIL-WATER-AIR-QUALITY NEXUS

The low use efficiency of fertilizer has strong adverse impacts on environmental quality. There exists a strong interconnectivity between soil, water, and air (Figure 1.1). Thus, decline in the quality of one leads to decline in the quality of the other two. Soil degradation, both due to natural and anthropogenic factors, is a serious global issue. It implies a decline in quality and functionality with the attendant weakening of essential ecosystem services or even creation of some disservices, and is a global issue of the twenty-first century with severe ramifications. Already 23% of ice-free land is prone to degradation (Bai et al. 2008). Among principal types of degradation (Figure 1.2), soil physical degradation (i.e., decline in soil structure and accelerated soil erosion by water and wind) are among the ramifications of the Anthropocene (Crutzen and Steffen 2003). Soil erosion by water is causing global transport of sediments at the rate of 36 Gt per year (Walling 2008). Heavy sediment load has strong implications for water quality (e.g., nonpoint source pollution and algal bloom) and air quality (emission of greenhouse gases, especially those of CH₄ and N₂O, the particulate matter), and is associated with the increase in the frequency and intensity of dust storms caused by acceleration of the wind erosion. Soil degradation, and the attendant decline in provisioning of ecosystem services and even generation of some severe disservices, also adversely impacts the use efficiency of fertilizers and uptake of nutrients and water by plant roots. Thus, reducing the risks of soil degradation and restoring degraded soils and desertified lands are high priorities. Soil degradation exacerbates contamination/eutrophication of water and pollution of air, because of the strong interconnectivity among them that leads to the cascading effect (Figures 1.1 and 1.2). Indeed, the quality of soil also determines those of water and air, and vice versa. Furthermore, quality of all three is a strong determinant of the fertilizer use efficiency, and of the use efficiency of nutrients applied and inherent in the soil.

FIGURE 1.1 Constituents of environment quality: Soil, water, and air.

FIGURE 1.2 The cascading effects of soil degradation on the deterioration of water, air, and plants, biodiversity, environment, and human well-being.

1.1.3 OBJECTIVES AND EXPECTED OUTPUT

The objective of this book, and specifically that of this chapter, is to deliberate the interrelationship between the use of chemical fertilizers on the properties and processes of soil, and the interrelationship between soil properties and processes on the use efficiency of fertilizer in general and of essential plant nutrients in particular. The chapter and the book are based on the hypotheses that (1) fertilizer demand can be reduced and efficiency enhanced by reducing the processes of soil degradation (Figure 1.3); (2) an increase in soil organic carbon (SOC) concentration in strongly and severely depleted soils (SOC concentration < 1 g/kg in 0–20 cm depth) would increase fertilizer and nutrient use efficiency; (3) integrated nutrient management (INM), that is, judicious combination of organic amendments and chemical fertilizers, is the best strategy to sustain productivity and reduce the environmental footprint of agroecosystems; and (4) carbon, nitrogen, phosphorus, sulfur (CNPK) is a better recommendation for plant nutrients and soil fertility management than that of nitrogen, phosphorus, sulfur (NPK).

FIGURE 1.3 Constituents of soil organic carbon.

1.2 GLOBAL FOOD DEMAND

Global food demand is increasing because of the growing and increasingly affluent world population. Starting from the beginning of world agriculture about 10 to 20 millenia ago, the world population is now projected to reach 7.8 billion in 2020. The world population is projected to reach 8.5 billion by 2030, 9.7 billion by 2050, and 10.9 billion by 2100 (UN 2019). It is argued that between 2005 and 2050, global grain production may have to be increased by 60% and as much as doubled in some developing countries. That being the case, there is additional demand for arable land area, fertilizers, pesticides, irrigation water, and energy use (Alexandratos and Bruinsma 2012). However, rather than appropriating additional resources to be used for agricultural production, a better strategy would be to narrow the yield gap from existing lands by adopting proven technology so that resources saved (i.e., land, water, and energy) can be saved for nature (Lal 2016, 2018).

1.2.1 TRENDS I...