Lockhart and Wiseman's Crop Husbandry Including Grassland

Steve Finch,Alison Samuel,Gerry P. Lane

• Publisher: Woodhead Publishing
• Year: 2014
• ISBN:
  9781782423928
• Edition: 9
• Topic: Biological Sciences
• Subtopic: Ecosystems & Habitats
• Index: Biological Sciences

Increased yields, markets, and profitability have led to changes in crop husbandry. Since its first publication in 1966, revised editions of Lockhart & Wiseman's Crop Husbandry Including Grassland have upheld and increased the book's good reputation. This ninth edition maintains its status as the standard textbook for many agricultural courses.

Partone covers the principles of crop production with chapters concerning plants, climate, soil management, fertilizers, manures, weeds, and diseases threatening farm crops. Parttwo surveys crop husbandry techniques. Environmental impact has been addressed in greater detail in this edition. This section looks at issues such as sustainable crop management, precision farming, and organic crop husbandry. The way these general techniques apply to individual crops is explained in part three. This part considers a range of cereals, combinable break crops, root crops, industrial crops, and fresh produce crops. Partfour looks at the use of grassland and forage crops, with chapters considering arable forage crops, the characteristics of grassland, and the corresponding methods for establishing and improving grassland. This part also includes information regarding equine grassland management and conservation of grass and forage crops.

This ninth edition of Lockhart and Wiseman's Crop Husbandry Including Grassland is relevant for students throughout the United Kingdom and Europe. It is a useful reference book for agriculture National Diploma courses, Foundation Degrees, and BSc degrees, and is important for Masters level students entering agriculture from another discipline.

• The previous edition has been widely expanded and remains the standard text for general agriculture, land management, and agri-business courses
• Includes new chapters on cropping techniques, integrated crop management and quality assurance, seed production and selection, and the influence of climate
• Discusses basic conditions for crop growth, how techniques are applied to particular crops, the influence of weather, and the use of grassland

Part I

Principles of crop production

Outline

1 Plants

2 Climate and weather

3 Soils and soil management

4 Fertilisers and manures

5 Weeds of farm crops

6 Diseases of farm crops

7 Pests of farm crops

1

Plants

Abstract:

This chapter describes the biology of plants, the most important organisms on the planet. It covers plant physiology and important biochemical processes such as photosynthesis and respiration. It describes the grouping of plants depending on their life cycle. It discusses the structures which are of most importance to crop production including seeds, roots and leaves. The chapter stresses the importance of the leguminous plants and their role in improving soil fertility. Finally it describes the requirements of plants for growth and development, and how these are controlled by plant hormones.

Key words

physiology; photosynthesis; water; nutrients; plant structure; plant hormones

1.1 Introduction

Plants are living organisms consisting of many specialised individual cells. They differ from animals in many ways and a very important difference is that they can build up valuable organic substances from simple materials such as carbon dioxide and water. The most important part of this building process, called photosynthesis, is the production of carbohydrates such as sugars, starch and cellulose, along with oxygen. They have rigid cell walls enclosing a semi-permeable cell membrane which allows the passage of water through it (osmosis). They have specialised organs such as roots, stems and leaves, are mostly immobile and are primary producers of food in most land-based ecosystems.

1.2 Plant physiology

1.2.1 Photosynthesis

In photosynthesis a blue/green substance called chlorophyll A and a yellow/green substance called chlorophyll B use light energy (normally sunlight but sometimes artificial) to change carbon dioxide and water into sugars (carbohydrates) and oxygen in the green parts of the plant. The amount of photosynthesis per day which takes place is limited by the duration and intensity of sunlight, and the ability of the green parts of a plant to capture it. The amount of carbon dioxide available can also be a limiting factor. Shortage of water, low temperatures and leaf disease or damage can reduce photosynthesis, as can shading by other plants, e.g. by weeds in a crop. The cells that contain chlorophyll also have orange/yellow pigments such as xanthophyll and carotene, and brown pigments called phaeophytins which absorb different wavelengths of light than the chlorophylls. Crop plants can only build up chlorophyll A and B in the light, and so any leaves that develop in the dark are yellow and cannot efficiently produce carbohydrates. The yellowing of leaves (chlorosis) can also be caused by disease attack, nutrient deficiency or natural senescence (dying off).

Oxygen is released back into the atmosphere during photosynthesis and the process may be set out as follows:

(a) The light reaction (light dependent)
This takes place in the thylakoid membranes inside the ‘chloroplast’, an organelle found inside the cells of green tissue. Light provides energy for the chlorophyll molecule that releases electrons. These split water into oxygen and hydrogen.
The chemical reaction of this stage is:

$2{\mathrm{H}}_2\mathrm{O}\to 2{\mathrm{H}}_2+{\mathrm{O}}_2$ [1.1]

[1.1]

The hydrogen then moves into the next stage:

(b) The dark reaction (light independent)
This takes place in the watery stroma of the chloroplast. Here the hydrogen is combined with carbon dioxide by the Calvin Cycle to give carbohydrate and water:

$2{\mathrm{H}}_2+{\mathrm{CO}}_2\to {\mathrm{CH}}_2\mathrm{O}+{\mathrm{H}}_2\mathrm{O}$ [1.2]

[1.2]

The carbohydrates are simple sugars, which can be moved through the vascular system of the plant in solution to wherever they are needed. This process not only provides the basis for all food production but it also supplies the oxygen which animals and plants need for respiration. The simple carbohydrates, such as glucose, may be built up to form starch for storage purposes or as cellulose for building cell walls. Fats and oils (lipids) are formed from carbohydrates by a process of esterification which produces mostly triglycerides. These are usually found in seeds and are a form of concentrated energy. Protein material, which is an essential part of all living cells, is made from carbohydrates and nitrogen compounds and also frequently contains sulphur. These form amino acids which are held together in proteins by peptide bonds.

Most plants consist of roots, stems, leaves and reproductive parts and need a medium in which to grow. These media could be soil, compost, water where plants are grown hydroponically or even air, where the bare roots are sprayed with a fine mist of nutrients and water (aeroponics). In soil the roots spread through the spaces between the particles and anchor the plant. The amount of root growth can be phenomenal. For example, in a single plant of wheat the root system may extend to many miles.

The leaves, with their broad surfaces, are the main parts of the plant where photosynthesis occurs (Fig. 1.1). A very important feature of the leaf structure is the presence of large numbers of tiny pores (stomata) on the surface of the leaf (Fig. 1.2). There are usually thousands of stomata per square centimetre of leaf surface. Each pore (stoma) is oval-shaped and surrounded by two guard cells. The carbon dioxide used in photosynthesis diffuses into the leaf through the stomata. Most of the water vapour leaving the plant, as well as the oxygen from photosynthesis, diffuses out through the stomata.

Fig. 1.1 Photosynthesis.

Fig. 1.2 Stomata on leaf surface.

1.2.2 Transpiration

The evaporation of water from plants is called transpiration. It mainly occurs through the stomata and has a cooling effect on the leaf cells. Water in the cells of the leaf can pass into the pore spaces in the leaf and then out through the stomata as water vapour (Fig. 1.3).

Fig. 1.3 Cross-section of green leaf showing gaseous movements during daylight.

The rate of transpiration varies considerably. It is greatest when the plant is well supplied with water and the air outside the leaf is warm and dry. When the guard cells are turgid (full of water) the stomata are open. When the plant is under drought stress the guard cells lose water and the stoma closes, slowing down the loss of water vapour (transpiration) from the plant. It also slows down the rate of photosynthesis. The stoma also close in very cold weath...