Plant nutrients crop response

Generally, nutrient deficiencies or excesses are caused by soil properties, fertilizer application, interactions between mineral elements during uptake and metabolism, and intrinsic factors of plants and crops with intensive nutrient responses. The rules of these element-specific influences were given by Bergmann (1992). 

The book reviews our knowledge of the chemistry and mineralogy of Mo, the extraction of available Mo from various soils, the various analytical methods of determining Mo content in soils and plants, the biochemical role of Mo in crop production, the technology and application of Mo fertilizers to crops, the responses to Mo of various temperate and tropical crops. Mo deficiency and toxicity in various plant species, the interaction of Mo with other plant nutrients, and the distribution of Mo within the plant. Factors affecting the availability of soil Mo to plants and Mo status in the semiarid and subhumid tropics are also discussed. 

Sulphm is an important plant nutrient (involved in the build-up of amino acids and proteins in the plant), a deficiency of which can limit the response of the plant to nitrogen. Sulphur deficiency has become more pronounced in some, but not all, crops in the last two decades. The natural build-up of sulphm in the plant is now much less because purer fertiliser is being used and the plant itself is growing in a less polluted atmosphere. It is, however, generally only necessary in areas away from industry and then perhaps for certain crops such as second and third cut grass for silage and oilseed rape. 

Soil Nutrient. Molybdenum has been widely used to increase crop productivity in many soils woddwide (see Fertilizers). It is the heaviest element needed for plant productivity and stimulates both nitrogen fixation and nitrate reduction (51,52). The effects are particularly significant in leguminous crops, where symbiotic bacteria responsible for nitrogen fixation provide the principal nitrogen input to the plant. Molybdenum deficiency is usually more prominent in acidic soils, where Mo(VI) is less soluble and more easily reduced to insoluble, and hence unavailable, forms. Above pH 7, the soluble anionic, and hence available, molybdate ion is the principal species. 

Neutral interactions are found extensively in the rhizosphere of all crop plants. Saprophytic microorganisms are responsible for many vital soil processes, such as decomposition of organic residues in soil and associated soil nutrient mineralization/turnover processes. While these organisms do not appear to benefit or harm the plant directly (hence the tenn neutral), their presence is obviously vital for soil nutrient dynamics and their ab.sence would clearly influence plant health and productivity. 

The increased growth response documented in almost all the solarization studies is mainly due to the above-cited higher levels of macronutrients or the improved uptake of micronutrients solubilized by humic substances (Chen and Aviad 1990 Chen et al. 1991). As a consequence of the enhancing effect of solarization on soil nutrients, Flores et al. (2007) suggested the application of low rates of mineral fertilizers before heating soil, in order to avoid an increased vegetative growth of the plants at the expense of crop yield. 

Subsoils vary widely in their ability to support plant growth. In some cases the addition of adequate nutrients will result in good crop growth. However, many other subsoils are problem soils and may support only a limited vegetative cover. Some of the reasons for the wide differences in plant response, mentioned in part above, are discussed in the following pages. 

One of the consequences of this approach is that the actual benefits of fertilizers are over estimated in fertility trials relative to when they are used by farmers. In addition, the resulte from adverse years v en no or poor response to fertilizer occurs are usuatty not reported because weather caused no response to the nutrient. Unfortunately, farmers cannot make decisions under a similar lack of constraints they must make investment decisions regarding seed, pesticides, labor, and fertilizer ir uts in a total farm management context. To majd-mize the benefits from management factors, the limiting factors should be in balance with each other, e.g., the crop variety must be able to benefit from the fertilizers used. Weed and insect control, plant density, water availability, tillage, and other management practices should be adequate for the farmer to realize a profit from fertilizer use. 

Increased knowledge about secondary nutrients and micronutrients, including plant requirements, nutrient sources, and methods of application, has resulted in th increased use. Improvements In soil testing and plant analyses have provided more knowledge about plant needs and the unde variations in plant responses to these nutrients. Higher crop yields and the use of h h-analysis NPK fertilizers also have resulted in increased needs for these nutrients. 

Abstract Cadmium is an important poiiutant in the environment, toxic to most organisms and a potential threat to human heaith Crops and other plants take up Cd from the soil or water and may enrich it in their roots and shoots. In this review, we suimnarize natural and anthropogenic reasons for the occurrence of Cd toxicity, and evaluate the observed phytotoxic effects of plants growing in Cd-supplemented sou or nutrient solution. Cd-induced effects include oxidative stress, genotoxicity, inhibition of the photosynthetic apparatus, and inhibition of root metabolism. We explain proposed and possible interactimis between these modes of toxicity. WhUe discussing recent and older studies, we further emphasize the environmental relevance of the experiments and the physiological response of the plant. 

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