Nutrients plant-growth

Onuf, C. P., Teal,., and Vahela, I. (1977). Interactions of nutrients, plant growth, and herbivory in a mangrove ecosystem. Ecology 58, 514—526. 

The value of langbeinite as a fertilizer is enhanced because, in pure form, it contains 18.8 wt % potassium, 11.7 wt % magnesium, and 23.0 wt % sulfur. AH three elements are essential nutrients for plant growth. Commercial grades contain ca 97 wt % mineral the remaining 3 wt % consists of water-insoluble clays and residual sodium chloride. 

Another area where improved air quaUty has impacted on sulfur use is ia agriculture. As sulfur dioxide emissions have decreased, sulfur content of soils has also decreased. Sulfur, recognized as the fourth most important plant nutrient, is necessary for the most efficient use of other nutrients and optimum plant growth. Because many soils are becoming sulfur-deficient, a demand for sulfur-containing fertilizers has been created. Farmers must therefore apply a nutrient that previously was freely available through atmospheric deposition and low grade fertilizers. 

In hospitals, chemical analysis is widely used to assist in the diagnosis of illness and in monitoring the condition of patients. In farming, the nature and level of fertiliser application is based upon information obtained by analysis of the soil to determine its content of the essential plant nutrients, nitrogen, phosphorus and potassium, and of the trace elements which are necessary for healthy plant growth. 

This represents not only a loss of an essential nutrient for plant growth, but the ammonia is capable of generating alkalinity in rainfall (8). Because of the low rainfall in arid regions, this ammonia is likely to be transported for long distances before affecting the pH of the rainfall (8). 

The cycles of carbon and the other main plant nutrients are coupled in a fundamental way by the involvement of these elements in photosynthetic assimilation and plant growth. Redfield (1934) and several others have shown that there are approximately constant proportions of C, N, S, and P in marine plankton and land plants ("Redfield ratios") see Chapter 10. This implies that the exchange flux of one of these elements between the biota reservoir and the atmosphere - or ocean - must be strongly influenced by the flux of the others. 

C04-0153. Phosphorus is essential for plant growth, and it is often the limiting nutrient in aqueous ecosystems. 

Plants are highly sensitive to soil acidity because many equilibria involving plant nutrients are affected by pH. Phosphorus is a primary example. This essential element for plant growth occurs in soils mainly as phosphates, which are subject to phosphate-hydrogen phosphate equilibria. Consequently, phosphorus is... 

It is well known that chemical compo.sition of rhizosphere solution can affect plant growth. Particularly, uptake of nutrients may be considerably influenced by the ionic concentration of the rhizosphere solution (40). Despite the difficulty of defining the exact concentration of ions in the rhizosphere surrounding each root (or even root portion), it has been unequivocally demonstrated that plants have evolved mechanisms to cope with the uneven distribution of ions in the root surrounding in order to provide adequate supply of each essential nutrient (41). These mechanisms include expression of transporter genes in specific root zones or cells and synthesis of enzymes involved in the uptake and assimilation of nutrients (40,43). Interestingly, it has been shown that specific isoforms of the H -ATPase are expressed in the plasma membrane of cell roots it has been proposed that the expression of specific isoforms in specific tissues is relevant to nutrient (nitrate) acquisition (44) and salt tolerance (45). 

This chapter considers the various types of root products with a potential functional role in the usually tough environment of soil. Only direct effects of immediate benefit to plant growth—e.g., an increase in nutrient solubility—are considered here. Although root products of a plant species may have a direct effect on important groups of soil organisms, such as rhizobia and mycorrhizae. their effect on the plant is not immediate these and aspects related to microbial activity in the rhizosphere are not considered here (see Chaps. 4, 7, and 10). For an extensive and recent review of the microorganisms in the rhizosphere, the reader is referred to Bowen and Rovira (23). 

This chapter focuses on the effects of humic substances present at the rhizo-sphere on plant growth and nutrient uptake. The main structural features of humic substances, their nutritional function, and the capacity to interact with plant metabolism are also presented. 

Humic substances have been proved to stimulate plant growth and nutrient accumulation (for review see Refs. 4,49, and 50). Various studies performed on excised roots or whole plants show that usually the uptake of cationic and anionic... 

Table 2 Changes in Plant Growth Parameter in Response to Iron Stress for Barley Plants Grown in Chelator Buffered Hydroponic Nutrient Solutions...

M. van Noordwijk and S. C. van de Geijn, Root, shoot and soil parameters required for proeess-oriented models of crop growth limited by water or nutrients. Plant Soil I8S (1996). 

D. Robinson and M. M. I. Van Vuuren, Responses of wild plants to nutrient patches in relation to growth rate, Inherent Variation in Plant Growth Physiological Mechanisms and Ecological Consequences (H. Lambers, H. Poorter and M. M. I. van Vuuren, eds.), Backhuys Publishers, Leiden, 1998, p. 237. 

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