Sugarcane is one of the major crops, which is mainly grown for sugar’s industries by providing them raw material for preparing sugar and other products in Pakistan.
Our sugar industry is the second largest sector after textiles. Sugarcane is tall perennial grass which is usually grown under warm climate (tropical areas). Its height is between 2-6 meter and internodes are rich in sucrose contents. In Pakistan, it is growing in a large area (1313 thousand hectares) after wheat, rice and cotton.
From last few years, the area and production of sugarcane is increasing day by day due to the good economic return and timely payment to the farmer. In the World, Pakistan is fifth largest country of producing sugarcane after Brazil, India, China and Thailand.
In Pakistan, it is third largest crop which shares about 0.7% in GDP of Pakistan after wheat and cotton. It also shares 3.6% in the total agricultural production. It provides raw material for sugar industry and also provides employment for the farmers throughout the whole year. It is used as a fertilizer, bio-fuel and fiber besides providing raw material to sugar industry.
The juice of sugarcane is used for making gur and shakar and the tops are used for feeding animals. During processing of sugarcane in sugar industry, different types of byproducts such as filter-cake, molasses, bagase and wax, are also produced which are used for making soil rich with organic matter, macro and micro-nutrients, paper, clipboard, fuel, fertilizer, alcohol and shoe polish. Compost can also be prepared by using sugarcane trash for improving the soil fertility and crop growth and yield.
Morphology
- Root system
Sugarcane has fibrous roots and these roots are of two types i.e. sett roots and shoot roots. Sett roots are produced from root primodia (at the base of cane) after planting and covering of cane setts from soil. These roots are thin in nature, have many branching roots and remain active for specific period of time. The main function of these roots is to provide water and nutrients to the primary shoot.
After this, these roots are died and new roots are formed from the lower rings of lower nodes of shoot. Lower ring’s roots move downward and upper ring’s roots move upward near the soil surface to support the cane stalk. These roots are known as shoot roots. These are thick, permanent and less branched while sett roots are thin, temporary and highly branched.
- Stalk
It is also known as “millable cane” and produced from the cane setts containing 1-3 buds/cane, after planting. Primary stalk is produced from the sprouting of these buds and secondary stalk is produced from the primary stalk.
Cane has small portion below the soil known as rootstalk. Sugarcane stalk contains nodes, internodes, flowers and leaves. Node is the base of leaf and contains a germination bud (eye) and this bud is wrapped with the leaf sheath.
Each bud has a leaf scar on the lower side. On each bud, there is germination pore from which sprouting takes place. Node contains a root band, bud, wax band and growth ring. Root band from which root primodia is formed, laterly, it develops into sett roots.
The internodes are covered with the leaf sheath and are of different shapes like curved, bobbin, cylindrical and conidial. Tapering of the root stalk starts rapidly and the shoots are developed from the lateral buds. These shoots are called as tillers.
- Leaves
Leaves of sugarcane consist of a leaf blade and a leaf sheath. Each leaf is produced from the node of cane stalk and grow, alternately. Leaf sheath completely, covers the internode and usually, hairy on the outerside. It is dark green in color.
Leaf blade is 1-2 meters in length and 0.05-0.07 meters in width and has color ranges from yellowish green to dark green. Its edges are serrated and midrib is well prominent. At the point of attachment of leaf sheath and leaf blade, there are auricles ( often hairy) on the outside and one ligule inside.
- Inflorescence
It is known as arrow which is an open panicle. It is 0.3m in length and tapered. Recemose is the spikelets arrangement (old flowers and young flowers at the bottom and top, respectively) and both male and female parts are present on the stalk but not all produce fertile pollen.
Some varieties have the ability to produce fertile pollens but they are small in size and remain viable for a very short period of time. Therefore, sugarcane is grown vegetatively, by using the cuttings/setts of cane.
- Cane
It is thick, oval in shape and slightly staggered. It has a small cavity known as pith, hard rind, red blotches and growth ring yellowish and root zone purplish yellow in color. Growth ring is slightly swollen. Usually, the width of growth ring and root zone is equal.
It is cylindrical to conidial in shape. Cane contains a wax band which is tapered and often merges with general bloom. Root zone present on cane is narrow, tapered and having two rows of eyes.
Growth stages
Sugarcane is a C4 plant and it has four critical growth phases which are given as following:
- Germination phase
This phase starts 7 to 10 days (10% sprouting) after planting and continues till 30-35 days (75% sprouting) with base temperature of 12 ºC. It is denoted by the sprouting of the vegetative buds and these buds are affected by two types of environment i.e. internal and external environment.
Internal factors include health, moisture, nutrients presence of the setts and external factors include temperature, moisture and aeration of soil. Warm and moist environment and porous soils are very suitable for germination.
About 28-30 ºC is optimum temperature for the sprouting of vegetative buds. When germination is about 60%, then it gives maximum yield. Cuttings are used for sugarcane which should contain at least three buds for better germination, growth and development.
- Tillering phase
This phase starts (just after first sprout) from 45 days after planting and continues till 120 days after planting. Eight to forty sprouts are formed during this phase depending upon types of varieties. Usually, strong-bushy, medium-bushy and weak-bushy cultivars/varieties produce 20-40, 15-25 and 8-12 sprouts respectively.
Tillering produces appropriate number of stalks for producing good yield. It is affected by many factors like temperature, light, variety, irrigation and fertilizers. From these factors, light is the most important factor affecting the tillering. Tillering requires temperature about 30 ºC and below 20 ºC tillering is stopped.
When temperature is optimum, it produces early and maximum tillers which give good quality and better yield. Usually 6-8 tillers are formed from one bud and only 1-2 tillers are developed in canes later, other dies off. When there is a ratoon crop, then it encourages early and maximum tillers.
- Grand growth phase
Only 15-20% tillers survive and grow well into canes to produce economic yield. It starts from 120 days and continues till 270 days. Under good climatic conditions, stalk of cane produces 4 to 5 internodes in one month. But if there is drought, the internode length is reduced to great extent.
This phase is most important phase because all processes like stem elongation and yield formation are taking place in this phase. This stage requires around 30 degree centigrade temperature with high humidity (80%) for better growth and development and plant reaches its maximum leaf area index in this stage (7-8).
- Maturity and ripening phase
This stage starts from 270 days after planting and continues till about 360 days. In this phase, vegetative growth is reduced and accumulation of sugar is increased and cane stalks converts simple sugars (fructose, glucose) into sucrose.
There is more quantity of sugar in the lower parts and low in the higher or upper parts of sugarcane because sugarcane stalk ripening starts from bottom to top. More sunshine hours with high temperature during day and low temperature during night are required for this phase.
Authors: Tanveer Ahmad*, Prof. Dr. Ashfaq Ahmad, Muhammad Shaukat and Muhammad Akhlaq Mudassir
*Agro-Climatology Lab, Department of Agronomy, University of Agriculture, Faisalabad