Fertilisers are chemical compounds given to plants to promote growth; they are usually applied either through the soil, for uptake by plant roots, or by foliar feeding, for uptake through leaves
Fertilisers can be organic (composed of organic matter), or inorganic (made of simple, inorganic chemicals or minerals).
They can be naturally occurring compounds such as peat or mineral deposits, or manufactured through natural processes (such as composting) or chemical processes (such as the Haber process).
These chemical compounds leave lawns, gardens, and soils looking beautiful as they are given different essential nutrients that encourage plant growth.
They typically provide, in varying proportions, the three major plant nutrients (nitrogen, phosphorus, potassium: N-P-K), the secondary plant nutrients (calcium, sulphur, magnesium) and sometimes trace elements (or micronutrients) with a role in plant or animal nutrition: boron, chlorine, manganese, iron, zinc, copper, molybdenum and (in some countries) selenium.
Both organic and inorganic fertilisers were called manures derived from the French expression for manual tillage, but this term is now mostly restricted to organic manure.
Though nitrogen is plentiful in the earth's atmosphere, relatively few plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a biologically useful form).
Most plants thus require nitrogen compounds to be present in the soil in which they grow.
Soils need phosphate and other nutrients.
When farmers apply nutrients, either in organic or mineral form, it is to fertilise the soil, not the plant.
The soil then acts as a conversion system for the crops, receiving, storing, transforming, transporting and exchanging plant nutrients.
A fertiliser formula, targeted towards the needs of a specific crop, may not reach the plant in the desired proportions.
The original composition may be modified, prior to the uptake by roots, through adsorption, fixation, leaching, volatilisation, and reduction, all processes which are governed by a combination of the chemical, physical and biological properties which characterize different soil groups.
The key to growing crops that are plentiful and that contain the nutrients we need is to assure that the local soil has the nutrients it needs.
Manure and compost, for example, typically have, and provide, relatively low nutrient content in comparison to commercial fertilizer.
If enough is spread, it may provide adequate nitrogen, but likely will not provide enough phosphate.
Where animal and crop production are integrated on a farm where organic farming is employed, manure or compost can be hauled daily to the fields or be stored until soil conditions are suitable to apply them.
This practice can provide organic matter and plant nutrients for the small or specialised farm, if it is used in conjunction with an organic phosphate source such as bone meal.
It is, however, more expensive and labour-intensive to collect, handle, store, transport and spread enough manure or compost to fertilise a large-scale agricultural field and provide other nutrient supplements.
Meanwhile, too much manure or compost in one location will increase the likelihood of polluting the groundwater with the nitrates and/or pathogens borne by the materials.
Mineral fertilisers are needed to maintain the level of soil fertility needed to meet the nutritional needs of the world's population.
Phased release phosphorous fertilisers are ideally suited to provide the crop with its immediate phosphorous requirements from the water-soluble proportion and, at the same time, maintain the soil phosphorous reserves from the longer lasting source.
Phased release phosphorous will also minimise phosphorous losses to the environment and, by providing available phosphorous throughout the season, will increase the uptake and utilisation of nitrogen.
Phosphorous is present in a number of forms, most commonly as monoammonium phosphate, diammonium phosphate, dipotassium phosphate.
The level of these phosphates needs to be determined accurately at point of manufacture.
Analysis of these phosphates can be difficult; however, an accurate and reproducible method has been developed.
This easy to use method relies on the thermometric titration of these phosphates.
The sample is titrated with a solution of Mg(NO3)2 to an exothermic endpoint in presence of an excess of ammonium ions.
What is a thermometric titration?.
Titration is the oldest and most widespread method used in analytical chemistry.
For a long time now, potentiometric sensors (indicator electrodes) have been used to cover a wide range of applications in the titration field.
As a result, potentiometric titration has become an established analytical method and features in many standards.
The electrochemical potential is only one of the possible ways of following a chemical reaction.
A far more universal parameter is the reaction enthalpy.
Every chemical reaction is accompanied by a change in enthalpy.
As long as the reaction takes place, this results in either an increase (exothermal reaction) or decrease (endothermal reaction) in the temperature of the sample solution.
For a simple reaction this means that the increase or reduction in temperature depends on the converted amount of substance.
The 859 Titrotherm from Metrohm is a USB-enabled thermometric titrator with one measuring input each for Thermoprobe and potentiometric sensor; four MSB connections for 800 Dosino and stirrers.
Titrotherm software (English dialog), Thermoprobe and USB connecting cable for PC is included.
Metrohm says its Dosino technology has defined a new standard for volumetric titration.
The Dosing Unit with its drive motor is mounted on the reagent bottle and thus guarantees maximum precision with minimum space requirements.
The titrator and two burettes require hardly more bench space than a sheet of DIN A5 paper.
Thermoprobe - quick, precise and robust.
Thermoprobe, a temperature sensor based on semiconductor technology (thermistor), has a short response time of 0.3s and a high resolution of 10-5K.
This makes the Thermoprobe the ideal sensor for thermometric titration, as it can follow any change in temperature quickly and accurately.
The housing made of polypropylene (PP) and epoxy resin provides the sensor with outstanding resistance to many organic solvents and aggressive media.
The software - everything at a glance, everything under control.
The clearly laid out Titrotherm software allows adaptation of the screen view to the particular method parameters and thus provides rapid access to important commands or parameters.
The endpoints are determined by calculating the first and second derivatives of the titration curve; by means of additional optimisation parameters, the reproducibility can be improved even further.
For report generation, the titration data can be exported manually or automatically into a freely arranged, method-specific report form.
