土壤学第九章 土壤养分(英文版)

全文电子教材

土壤与土壤资源学

（上篇：土壤学）

林学专业

2 O 2

SO

2

H 2O

O 2

Mineral

Nutrients

英文版—土壤养分

Chapter 9. Soil Nutrients

Soil nutrient availability is one of the factors that often limit tree growth and soil productivity. Other factors commonly limiting for tree growth can include soil moisture availability, climate (such as temperature and precipitation), soil physical properties (such as drainage and soil compaction), or a combination of the above factors. N is often a nutrient that is most deficient for plant growth. Nitrogen deficiency can be caused by low N content in the soil or by the slow release rate in ecosystems such as the boreal forests or peatlands where low temperature or poor aeration encourages accumulation of organic matter and reduces N mineralization rates. Phosphorus is also frequently deficient in soils where there is very little P in the parent material or where most of the P has been lost through weathering during the soil formation processes, such as in the tropics.

There are 16 elements that are considered essential for plant growth. Lack of any of those essential nutrients will hinder the proper growth and functioning of the plants and will prevent the plants from completing their life cycle. Among those 16 essential nutrients, C, H, and O come from the air and water and are usually not deficient, although recent climate change studies using CO2 enriched air showed that increasing atmosphere CO2 concentration can significantly increase forest productivity; however, plants usually acquire the other essential nutrients from the soil. Among the macronutrients (N, P, K, Ca, Mg, and S), Mg and S can also sometimes be deficient for tree growth. Potassium and calcium deficiencies in forests are very rare. In terms of micronutrients (Mn, Zn, Cu, Fe, Mo, B, and Cl), B, Zn, Cu, and Fe deficiencies, especially B deficiency, are most frequently reported. These nutrients are called micronutrients because they usually exist on the earth and are required by plants in very small quantities. In addition to those 16 essential nutrients, cobalt (Co), vanadium (Va), nickel (Ni), silicon (Si), and sodium (Na) have been found to be essential to some plants. For example, nickel has been found to be essential for soybeans and Si for rice. In this chapter, we will discuss the importance of soil nutrients in tree growth, discuss the macronutrients and micronutrients, describe the cycling of nutrients in the soil, and provide an introduction to the mechanisms of plant nutrient uptake.

9.1 Nutrients: available forms, availability and functionality

The interaction of numerous physical, chemical, and biological properties in soils controls the availability of soil nutrients for plant uptake. Understanding these processes will enable us to manage selected soil properties to optimize nutrient availability and soil productivity. To understand these interacting processes will require us to have a good knowledge of the soil properties and processes covered in the earlier chapters. Not all nutrients present in the soil are available for plant uptake and different nutrients have different available forms.