These are the elements that plants need to survive. Essential elements, whether in large amounts or in minute quantities, are chemical elements that plants need in order to complete their normal life cycle . The functions of these elements in the plant cannot be fulfilled by another. Thus making the element essential for the plant growth and development.

Elements that are needed in large quantities are called macronutrients while those in minute or trace quantities are called micronutrients.

Below is a table of the essential elements of plants.

Name	Symbol	Atomic number	Atomic weight	Classification	Importance to plants
Nitrogen	N	7	14.01	Macronutrient	Constituent of chlorophyll, amino acids and nucleic acids
Potassium	K	19	39.10	Macronutrient	Stimulates a number of enzymatic activities; involved in opening of stomata
Calcium	Ca	20	40.08	Macronutrient	Contributes to cell membrane stability, cell wall rigidity, and cell division
Magnesium	Mg	12	24.31	Macronutrient	A major component of chlorophyll; activates enzymes for respiration, photosynthesis, and DNA synthesis
Phosphorus	P	15	30.97	Macronutrient	Component of membrane phospholipids, nucleic acids, sugar phosphates, ATP, & ADP
Sulfur	S	16	32.07	Macronutrient	Component of some amino acids and some coenzymes for the plant’s metabolic and synthetic processes
Chlorine	Cl	17	35.45	Micronutrient	Involved in water-splitting reaction in photosynthesis, cell division, osmoregulation, and closure of stomata
Iron	Fe	26	55.85	Micronutrient	Component of proteins involved in photosynthesis, respiration, & nitrogen fixation; required for chlorophyll synthesis
Boron	B	5	10.81	Micronutrient	Involved in sugar transport, cell wall synthesis, carbohydrate metabolism, & pollen tube growth
Manganese	Mn	25	54.94	Micronutrient	Required for photosynthetic evolution of oxygen; cofactor in many enzymes
Zinc	Zn	30	65.39	Micronutrient	Component of many enzymes; involved in gene regulation
Copper	Cu	29	63.55	Micronutrient	Cofactor of enzymes involved in redox reactions; involved in cell wall lignifications
Molybdenum	Mo	42	95.94	Micronutrient	Catalyst for nitrogen metabolism
Nickel	Ni	28	58.69	Micronutrient	Component of urease and hydrogenase; involved in mobilization of nitrogenous compounds

Reference:  Alejar, A.M.A. and Sese, M.L.D.(1999).Fundamentals of plant physiology. Philippines: Plant Physiology Society of the Philippines, pp. 77-90

Tags: Essential Elements, macronutrients, micronutrients

Weeds are also plants. The crops planted in the field are also plants so how can we differentiate a weed from a crop?

Weeds are found on land where the native vegetation has been replaced by a controlled system of cropping management. It is man who has forcibly altered the vegetation for other purposes mainly for agriculture. Crops, on the other hand, are plant that fit economically into the scheme of man’s work and existence. These plants are being managed to a certain degree. A plant species become a crop because man developed it to be a crop.

In the early days, weeds were not considered as pests in the field since: a) damage caused by weeds are not visible as those caused by insects and plant pathogens, b) crops are always associated with weeds, c) it is easier to see insects with crops than weeds, d) and there is seldom total crop failure due to weeds.

Damage of weeds to crops is not visible compared to insects that result to feeding trails and to diseases causing lesions and necrosis. When there is a crop, there is always a weed. That is why weeds were not considered as a threat to crop production. Sometimes, weeds look like crops so it is difficult to spot weeds in a heavily planted field. Unlike pests which are very noticeable in the field. Crop failure is less likely attributed to weed competition and there is seldom crop failure. These are some of the reasons why weeds were not regarded as pests before. At present, the direct and indirect contributions of weeds in crop failure have made it one of the pests considered in the field.

Rice bug is a significant insect pest in a rice field. It can reduce the total yield by 30% during harvest if not given attention by farmers. The insect feeds on rice at the milking stage (30-35 days after planting depending on the rice variety) of the plant leaving empty rice grains during harvest. Thus the reduce in the total yield.

A cheaper cultural method of controlling rice bug practiced by some farmers all over the Philippines is by dipping a cloth to a female urine and place it in sticks or poles placed in the boundaries of the field. The urine should come from a female who has already undergone menstruation or if she is already in her menstruation period. Farmers recommended using a wife’s urine as it is more effective than using an unmarried woman’s urine. Still, the latter’s urine can be used as long as she is already in puberty.

The reason for this is that male rice bugs are attracted to the female hormones secreted by the female rice bags. This hormone is similar to the human female hormone, thus, the male hormones will be attracted to the cloth (dipped in the female urine and stuck on a stick or pole) that you have placed in the boundaries of the field. By daytime, the male rice bugs will be gathered around these traps and you can manually kill the male rice bugs. Without the male rice bugs, there wont be any agents to fertilize the female rice bugs. Thus, the rice bug population will be reduced and that you don’t have to spend on additional costs for pesticide application. I hope this information helps.

Tags: rice, rice bug