A guide to identifying and managing nutrient deficiencies in cereal crops

An element is considered essential to plants when it is involved in plant metabolic functions, and its absence prevents plants from completing their life cycle (i.e., to grow and reproduce). Seventeen elements are most commonly identified as essential. These are, in order of relative concentration in plants: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), sulphur (S), chloride (Cl- ), iron (Fe), boron (B), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), and nickel (Ni). Other elements that have been identified as beneficial, but not necessarily essential to all plants, include cobalt (Co), selenium (Se), silicon (Si), sodium (Na), vanadium (V), and aluminium (Al). Among this list, N, P, and K are considered the primary macronutrients; Ca, Mg, and S are considered secondary macronutrients; and the remaining are micronutrients, but this does not mean that they are less important. All the essential nutrients are required by plants in balan ed proportions for optimum growth. Nutrient deficiencies occur when insufficient quantities are available to meet the requirements of a growing plant and are often manifested as visual symptoms on plant parts. Such visual symptoms could take several forms, such as stunting, chlorosis, discoloration, or necrosis. They may be observed in the older or younger parts of the plant depending on the mobility of the nutrient within the plant. Recognizing nutrient deficiency in crop plants is often difficult for even the most experienced eyes. Multiple nutrient deficiencies can occur at the same time and some symptoms are similar for different elements, making it even more confusing. Nutrient deficiencies can also be confused with symptoms of disease, drought, excess water, genetic abnormalities, herbicide and pesticide damages, and insect attack. However, each deficiency symptom is related to some function of the nutrient in the plant. For example, stunting of plants occurs when a nutrient involved in plant functions uch as stem elongation, photosynthesis, and protein production is deficient. So understanding the basics of nutrient deficiency and sufficient field experience can make the task of nutrient deficiency identification easier. Multi-nutrient deficiencies in Indian soils are a major concern. Besides the obvious implication of yield loss of crops, such deficiencies, if not corrected with adequate external inputs, could cause serious damage to the soil quality. Along with the dependence on soil and plant testing, emphasis must be given to walking the fields and developing a trained eye to detect and interpret nutrient deficiency symptoms. Early detection of nutritional disorders through recognition of visual symptoms can allow quick correction of opted nutrient management strategies and prevent yield loss. This booklet on nutrient deficiencies of cereal crops, developed by the International Plant Nutrition Institute (IPNI) and International Maize and Wheat Improvement Center (CIMMYT), is designed as a field guide t identify nutrient deficiency symptoms of the major cereal crops in the field, to understand the underlying causes of such deficiencies and how they might be prevented or remedied. Excellent deficiency photographs provided by Dr. Manoj Kumar Sharma and Dr. Prakash Kumar of Department of Agriculture, Government of Rajasthan, and IPNI, will allow the user of this field guide to understand the development of nutrient deficiency symptoms through the growth stages of the crop. We expect that this book will be a useful reference for researchers and extension staff involved in cereal production and knowledge dissemination and will help minimize cereal yield losses due to nutrient deficiencies.