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Wednesday, May 19, 2010

Plants Growth Factor

Environmentally Factor determine plant to grow on earth are Light, Temperature, Water and Soil. The present and absent of these 4 factors also determine the distribution of crops by location, cropping pattern, management practices and level of inputs for a favourable conditions. It was the basic knowledge when I learn about basic agriculture subject in university 30 years ago. This article will discuss about the 4 factors with current issues.

1. LightSunlight is an essential for any crop. The amount of sunlight received by plants in particular region affected by the intensity of incoming light and the day length. In Malaysia and other equatorial region, the amount of sunlight is so much so that there was a Hugh variety of plants with green colours and supply oxygen to the world. Other region such as in Northern Pole there was less sunlight and not many vegetation there. The light intensity changes with elevation, latitude and season as well as other factors such as clouds, dusts, smoke etc. The total amount of light received by a crop plants is also affected by cropping system and crop density. For example dense cocoa planting may cause less fruiting capacity if not properly manage the light intensity under the Gliricidia spp tree due to over shading. Ornamental plants required plant shade in the nursery for this purpose.

Different plants differ in their light requirements. Full Sun plants thrive in full sun but grow poorly in shades. Paddy, Pineapple and Citrus are some examples plants need full sunlight to bear flowers and fruits. Partial Sun Plants will produce an edible crop when grow in shady location. However this plants needs about 50-89% sunlight to perform. Crop like cocoa, coffee, vanilla, leafy ornamental are the examples. I manage to involve in cocoa replanting programs in early 1980's to ensure cocoa was grown under coconut or orchard trees with 60-80% shades. Full shade plants thrive in 30-50% sunlight and are weaken under full sun. Shading sometimes is used to inhibit pigment development in crops.

Due to the tilt of earth's axis and its travel around the sun, the day length (also called photoperiod) varies with season and latitude. Photoperiods controls flowering and formation of storage organs in some species (Fruit, Tubers, Seeds ets). There is some explanation on this sun effect as Short-day Plants when the flower produced when day length decreases. Long-Day Plants flower when the day length increases and Day-Neutral plants are not affected by the day length and it able to flower under any light period.

2. Temperature

As we know the temperature influences in Photosynthesis, water and nutrient absorption, transpiration, respiration and enzyme activity. From my observation on vegetable farm at Sengkang recently, seems that the temperature also governs germination, flowering, pollen viability, fruit set, rate of maturation and senescence, yield, quality, harvest duration and shelf life. Different plants required different temperature requirement. My experience saw that Dates/ Pokok Kurma Arab cannot produce flower and fruit planted in Muar. Most crop species required usually at range around 25 Celsius. The extreme temperature was at 0 Celsius and the hottest at 40 Celsius. Temperature change in daytime and nighttime also has an effect on plant growth.

3. Water
As I know ,Water is absolutely essential for any plants to grow. Plants can be grouped according to their natural habitats with respect to water supply. Hydrophytes Plants are plants that are adapted to living in waters or in soil saturated with waters. The hydrophytes usually have large interconnected inter cellular gas-filles spaces in their root and shoot tissues (aerenehyma) to facilitate air exchange. Mesophytes are the most common terrestrial plants that are adapted to neither a long wet nor a long dry environments. Depending on the extension of the root systems and other plants features , however their water requirement are varies. Plants like paddy, mango, apple, banana, rubber and many others are the examples of mesophytes. Xerophytes are plants that can endure relatively long period of drought. Plants like cactus, resins and others usually has a special features such as swollen tissues, deep rooting system to conserved and find the water.

4. Soil
I manage to study as election subject in Soil. Soil is actually a medium that provide anchorage for the plants and supplies water and mineral nutrients for normal growth. Soils consists of mineral matter (N,P,K,Mg, Ca, and micro nutrients) , organic matters, air and water. The proportion of this 4 types mineral will determine the soil properties such as the soil types, pH and fertility. In Malaysia, soil classification determine all the characteristic subject to crop type suitability. There are Segamat Series, Jerangau Series, Briah Series, Rudua Series, Gajah Mati Series where explained the soil type in Malaysia.

Soil Type are divided to four group that is Clay, Clayey loam, Loam and Sand. Loam is composed of sand, silt and clay in relatively even amount. Soil type determine the soil capacity to store the water and nutrients, aeration, drainage and ease of field operation. From my observation sandy soil are easy in land preparation but very low in fertility and water holding capacity. Clayey soil however are more fertile and high water retention but poor in drained and aerated.

Soil pH is a measure of the soil acidity and alkalinity. It affects the availability of nutrient and nutrient uptake ability and existence of microorganism. The best soil pH between pH 6.6 - 7 where most nutrient available. Nutrients in the soil may be chemically tied up or bound to soil particles and unavailable to plants. Individual plants have pH preferences and grow best if planted soils that satisfy their pH requirements. Plants like pineapple able to grow on acidic soil.

Soil Fertility is the inherent capacity of soil to provide plants nutrient in adequate amounts in proper balance for the growth of specified plants. My experience shows that fertile soil are rich in NPK nutrients, trace elements, water and high organic matter such as on commercial vegetable farms in Ulu Tiram, Johor.

Soil Salinity refers to the presents of excess salts in soil water, which often results from irrigated agriculture. Soil salinity always measured in Electrical Conductivity (EC) of soil solution in desiemens per meter (dS/m). Excessive uptake of salts ma cause toxic effect on the plants. In Malaysia coastal area with Bris Soil (Sandy) are area with high potential of salinity. Few TKPM such as at TKPM Mersing, TKPM Rhu Tapai, TKPM Marang, TKPM Janglau are some area with salinity problems.


M Anem
Scientist on Agronomy


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