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SULPHUR AND ITS COMPOUND SULPHUR AND ITS COMPOUND:A.SULPHUR (S) Sulphur is an element in Group VI(Group 16)of the Periodic table . It has atomic number 16...






CROP PRODUCTION(IV):FIELD PRACTISES, Field practices. Operations carried out in the field to facilitate proper growth and optimum yield.


Growing of crops of different families on the same piece of land in an orderly sequence.  It is commonly carried out I n annual crops.

Solanacea (potato family) Tomatoes, Irish potatoes, tobacco, pepper, brinjals.
Graminae (grass family) Maize, sorghum, wheat, barley, rice, sugarcane.
Leguminosae (legume family) Beans ,peas ,groundnuts ,Lucerne ,cowpeas


Cruciferae (cabbage family) Cabbage, kales, spinach, lettuce, Chinese cabbage.

Importance of crop rotation.

  1. Maximum utilisation of nutrients.  

Different crops vary in their nutrient requirements in terms of depth of absorption and type of nutrients. Maize absorbs a lot of nitrogen and low potassium while cassava absorbs a lot of potassium and less N. deep rooted crops absorbs nutrients from deeper layers of soil as compared to shallow rooted crops. Therefore alternating such crops ensures nutrients from different layers are utilised.

  1. Control of soil borne pest and diseases build up.

Crops of the same family are attacked by same pests and diseases.  To control such pests and diseases, such crops should be alternated with crops from different families.   iii. Control of weeds.

Parasitic weeds such as Striga spp (witch weed) are specific to grass family and can be controlled by planting non-grass crops. iv. Improvement of soil fertility.

Leguminous crops in rotation programme helps in fixing nitrogen thus improving soil fertility.

  1. Improvement of soil structure.

A grass ley (piece planted with grass) should be established at the end of the rotation programme. Roots of grass binds soil particles together improving its structure.

  1. Control soil erosion.

Crops such as maize planted in rows should be alternated with cover crops that protect the soil from agents of soil erosion.



  1. Crop root depth.

Deep rooted crops should be alternated with shallow rooted crops.

  1. Crop nutrients requirements.

Heavy/gross feeders should come first in a newly opened land that is relatively fertile.

  1. Weed control.

Crops associated with certain weeds should be alternated with those that are not. Alternate crops that are not easy to weed with those that are easy to weed.

  1. Pests and disease control.

Crops of the same family should not follow each other in a rotation programme because they are attacked by the same pest and diseases.

  1. Soil fertility.

Include a leguminous crop in the programme to improve soil fertility.

  1. Soil structure.

Include a grass ley at the end of the rotation programme to improve soil structure.


  1. Monocropping/monoculture.

Practice of growing one type of crop in a farm.


  • Leads to build up of pests and diseases if one crop is grown continuously.
  • The crop uses on the nutrients it requires leaving other nutrients unused.
  1. Intercropping.

Practice of growing two or more crops in the same piece of land at the same time.

Crops takes a long time together in the field.

Common intercrops include:

  • Maize-beans.
  • Banana- coffee.
  • Maize-beans-potatoes.

Advantages of intercropping. 

It offers better ground cover controlling soil erosion and smothering weeds.

  1. Mixed cropping.

Growing two or more crops in the same piece of land but in specific sections at the same time.



Placement of materials either organic or inorganic on the ground next to the growing crop.

Importance of mulching. 

  • Reduction of evaporation rate.
  • Smothers weeds.
  • Moderation of soil temperatures. Ø Reduction of speed of runoff.

Types of mulching materials. 

  • Organic mulching materials. Include: maize stalks, Napier grass sawdust and wood shaving.
  • Inorganic/synthetic materials. May be black or transparent polythene sheets.

Advantages of mulching.

  • Prevents water evaporation thus maintaining moisture in the soil for plant use.
  • Acts as an insulator thus modifies soil temperatures preventing fluctuation of day and night temperatures especially in bare soils.
  • Controls soil erosion by reducing the speed of running water and intercepting raindrops and increasing rate of infiltration.
  • Controls weds by suppressing their growth.
  • Organic materials decompose resulting into humus that improves soil structure and water holding capacity.
  • Organic mulch materials improves soil fertility by releasing nutrients after decomposition.

Disadvantages of mulching.

  • Provides a breeding ground and hiding place for pests that attack crops.
  • Traps light showers of rainfall thus lowering the chances of raindrops reaching the soil.
  • It is a fire risk.
  • Expensive to acquire, transport and apply.


  1. Thinning

Uprooting/removal of excess seedlings to allow space for the remaining seedlings.

Uproot when the soil is moist to avoid damage of roots of remaining seedlings.

Importance of thinning.

Reduces competition for growth resources. Which are space, light intensity, nutrients.

To achieve optimum plant population.

  1. Gapping

Filing or replacement of dead seedlings. Timely gapping should be done to prevent shading of the newly established plants especially in crops that do not tolerate shading such as tobacco.

Seeds fail to germinate because of:

  • Poor viability.
  • Attack by soil borne pests and diseases.

Gapping ensures optimum plant population.

  1. Rouging.

Uprooting and destroying infected plant. Destruction is by burning or burying deep in the soil.

Prevents spread of diseases that are difficult to control. E.g.

  • Armillaria root rot in tea.
  • Black rot in cabbages.
  • Maize smut in maize.
  • Maize streak virus.
  • Maize lethal necrosis disease.
  1. Pruning.

Removal of excess or unwanted parts of a plant.


Reasons for pruning. 

  1. To remove the diseased and unwanted parts of a plant. Annual pruning in coffee involves removal of suckers, branches and leaves that are excess old or diseased.
  2. To control cropping. Fruit crops have a tendency to bear biennially. This is due to unproportional ratio of vegetative and productive parts.  Pruning thus ensures uniform bearing.
  3. To facilitate picking. Perennial crops should be maintained at a convenient height for harvesting.eg tea and coffee.
  4. To train the plant so that it have the required shape. To restrict upward growth and encourage lateral growth especially in tae to have a uniform plucking table. Capping in coffee (38cm) encourages growth of suckers that develops into stems.
  5. To ease penetration of spray. Pruning opens up the bush making spray to penetrate easily. This economises on the use of spray.
  6. Control of pests and diseases. It eliminates Micro-climate that favours the breeding of pests.  Some diseases thrive best in humid, bushy dark parts of the plant.  g. CBD and antestia bug are controlled by open pruning.


Pinching out.

Removal of the terminal bud especially in tomatoes. Also carried out in fire cured tobacco. In tea and coffee it is called capping and it discourages upward growth and initiates lateral growth.

Annual pruning.

Removal of branches that have borne two crops and have undesirable growth characteristics.


Done in tree crops where branches are cut.

Coppicing. Cutting of the tree above the ground as a method of harvesting fodder.

Pollarding.  Cutting all the branches and the top of the tree.

Lopping.  Cutting branches from a tree in a haphazard manner.

N/B care should be taken when pruning to avoid injuring the crop.  This is because production will lower as the tree is trying to heal the wound.  Cut surfaces may be root of pathogens entry thus should be protected by application of paint or Stockholm tar.

Tools used in pruning. 

  1. Pruning saw, cutting hard branches and stems in coffee and citrus.
  2. Pruning knife. Cutting/pruning tea.
  3. Pruning shears. Trimming hedges.
  4.  Pruning/cutting soft branches in coffee and citrus. 



Plucking table formation in tea.

Formative pruning method.

Pegging method.

 Formative pruning method.

The plant is capped at different height to discourage vertical growth and encourage lateral growth. However it takes long to bring tea into bearing.

Pegging method.

Plant is allowed to grow for one year to a height of 25-30cm and then cut back 15cm above the ground. This encourages development of more branches which grow to 60-75cm which are then forced to grow at an angle of 30-45 by use of pegs.  Tips are nipped off to stimulate dorminant buds to grow into shoots.

 Methods of pegging.

  1. By use of individual hooked sticks.

Peg measuring 50cm long are used to hold the branches.  It requires a lot of pegs as each branch requires a peg.

  1. Use of rings and pegs.

A ring 30cm in diameter is used.  Ti is placed on branches that are gently forced to bend to the sides at an angle of 30-45.

3 pegs are used to hold it in position.  Tips of shoots are nipped off to encourage growth of more shoots.

  1. Use of parallel sticks (fittos) and pegs.

Two parallel light fitos are placed on either side of a row of bushes. Pegs hold the fitos down.  Light sticks (45cm) long are placed under the parallel sticks to hold in position any branches between the fitos.


Cutting back of shoots to the desired table height (20cm above the pegging height.)

Involves removing 3 leaves and a bud from each shoot above the required table height. The initial height is 50cm above the ground level. Two Y-shaped sticks 50cm in height and a long straight stick 2cm long are used as a guide in establishing a uniform plucking table.


Encourages formation of a uniform plucking table.

Maintenance of the plucking table.

Maintenance pruning.

Cutting back tea bush to 5cm above the last pruning height after 2-5 years.  3 months after tipping is done.


Cutting down the tree bushes down to 45cm above the ground to maintain the plucking table.  Done after every 40-50 years.

Pruning mature trees.

Points to consider.

  1. Side branches growing below the pruning height should never be cut back as it reduces spread of the bush and consequently the yield.
  2. The outside edge of the bush should not be cut at a higher level than the centre and there should be no attempt to have a dish-shaped frame.
  3. Small branches and twigs on the frame should be removed by hand. There should be no “cleaning up” of the frame with a knife after pruning.
  4. Pruning knife must always be sharp so that the branches are cut rather than broken.
  5. After several pruning, tea bushes should be cut back to the original table. (Change of cycle.).
  6. Branches should be cut across to minimise area of wound. Long slopping cuts tend to increase die back and the risk of fiction.
  7. The bushes should be pruned parallel with the slope and not a horizontal plane.
  8. All branches are left to rot in the field as they contain a lot of nutrients and also acts as mulch.
  9. Several branches should be placed on top of the frame to offer protection during the dry period. These should be removed as new shoots start to emerge.
  10. At regular intervals, tea bushes should be pruned back to 5cm above the previous pruning level. This avoid development of detrimental callus tissue.


Reasons for pruning coffee.

  1. To regulate bearing. Unpruned coffee produces a heavy crop in one season and a light one in the next season.
  2. To remove old and unproductive branches.
  3. To make harvesting easy by regulating the height of trees.
  4. Open pruning facilitates penetration of sprays.
  5. There is economic use of sprays.
  6. To open up the bush and bush and allow air circulation. This removes Micro-climate suitable for pest and disease organisms.

 Systems of pruning coffee.

  1. Single stem.
  2. Multiple stem.



 Involves establishing one permanent stem with a strong framework of primary branches. At each capping, the best growing suckers is allowed to continue growing upward.  Capping encourages development of a strong primary branches.

First capping    53cm

Second capping.  114cm Final capping.  168cm.

The final height is 1.5-1.8M.

The initial crop is borne on the primary branches.  As the bush matures, the main crop is borne on secondaries and tertiaries.  Annual pruning (done after harvesting) will involve removal of suckers, dead and damaged branches, those touching the ground and those with undesirable growth characteristics such as: those growing inwards, downwards, crossing and touching each other.  De-suckering is done throughout the year.

Advantages of single stem pruning.

  • Allows easy picking and spraying. Ø Minimises breakages of branches.


  • Requires skilled labour to establish.
  • Takes time to bring bushes into bearing.
  • Shade trees are required to avoid scorching of the top branches and the berries.


Aims at establishing 2 or 3 main upright stems with laterals to bear the crop.

Types of multiple pruning systems.

Multiple capped.

Multiple non-capped.

 Multiple capped.

The main stem is capped at 38cm and 2-3 shoots are allowed to grow to a height of 1.5-1.8M and then they are capped.

Multiple non-capped.

 The main stem is capped at 38cm, 2-3 shoots are allowed to grow and are not capped.

The crop is borne on the laterals crossing, dry, broken laterals are removed.  The stems grow tall and bend outward due to the weight of the crop. When stems get old, (4-6years) they are removed. (Changing the cycle).this involves pruning inner laterals to allow light penetration and encourage growth of new suckers

Annual pruning.  It will involve: removal of laterals that have borne 2 crops, those that are dry/broken.

Advantages of multiple non-capped system. 

  1. Requires less skills to establish.
  2. Easy to prune.
  3. Does not allow accumulation of CBD due to removal of old branches.


  1. Breakages of stems and branches.
  2. Difficulties in gathering berries from the top points.
  3. Difficulties in spraying the tall bushes.
  4. Rotting of stumps with age.


Process of cutting the main stem at a height of 53cm when the plant is 69cm tall.


Removal of suckers from coffee bushes.  Should be done as soon as they appear.

Changing the cycle.   

Replacement of the old bearing stems by suckers.  Done after every 4-6 years.

18 months before cutting down the old stems, suckers removal is stopped, 3 suitable and evenly spaced suckers are selected.  Inward pointing laterals should be cut higher towards the end of the cycle to allow light penetration and encourage development of healthy suckers.



Involves removal of extra suckers in the stool.  3-6 stems per stool is ideal.  They should be at different stages of development to ensure they come to bearing at different times.


  • Removal of extra suckers.
  • Removal of dry and diseased leaves.

Suckers should be cut deeply at the roots to stop them from regenerating. Use a sickle or panga for pruning in bananas.


Involves removal of old stems down to the level of the top foliage at the end of each year.  Failure to remove dead stalks results in:

  • Yield decline.
  • Increase in incidences of bud disease.


Practice of manipulating the plant to grow in a designed direction and shape.

Include: staking, propping, trelishing.

  1. Staking.

Staking is the practice of supporting plants having weak stems with the help of a thin strong stick.

Crops staked.

  • Tomatoes
  • Garden peas.
  • Tall/indeterminate bean varieties.
  1.    Propping 

Practice of providing support to tall varieties of bananas or those with heavy bunches using forked (Y-shaped) sticks.

  1. Trelishing

Practice of providing support to crops having vines by using wire or sisal strings.

EARTHLING UP.         

Placement of soil in form of a heap around the base of the plant.

Importance of earthling up.

  1. Promotes seed production in groundnuts.
  2. Prevent lodging in maize.
  3. Improves tuber formation in Irish potatoes and sweet potatoes.
  4. Improves drainage around the plant in tobacco.

Care should be taken not to injure the roots.


  1. Control of weeds.

Weed. Plant growing where they are not wanted and whose disadvantages outweigh the advantages.  Weeds compete with crops for growth resources and some act as alternate host of pests and diseases that attack crops.

  1. Control of crop pests.

Pest.  Living organism that is harmful to the crop.  Include: insects, nematodes, rodents, thrips, and mites.   They lower the quantity and quality of crop products, transmit crop diseases and increases the cost of production.

  1. Control of crop diseases.

Disease.  Any alteration in the state of an organism and function of a plant or its parts.

Categories of crop diseases.

  1. Fungal diseases.

Diseases caused by fungi.


  • CBD
  • Rust of maize.
  • Armillaria root rot.
  1. Viral diseases.


  • Ratoon stunting of sugarcane.
  • Rosette disease of groundnuts.
  • Cassava mosaic.
  • Maize streak virus.
  • Maize lethal necrosis disease.
  1. Bacterial disease.


  • Bacterial wilt in tomatoes.
  • Black arm of cotton.
  • Black rot in cabbages, kales etc.
  1. Nutritional deficiency.
  • Blossom end rot in tomatoes.



Factors determining stage/time of harvesting.

  1. Purpose of the crop.

Maize meant for silage making should be harvested before flowering while that for grain production should be harvested after grains mature.

  1. Market demand.

Consumer’s preference should be considered e.g. maize can be harvested while green or when dry depending on the market demand.

  1. Concentration of the required chemical.

The part being harvested in relation to the chemical required.  In coffee the ripe berries provide the required caffeine while in tea two leaves and a bud give high quality tea leaves.

  1. Weather conditions.

Crops should be harvested during the dry spell to prevent losses. Planting should be timed so that the crop matures in the right time. (Synchronisation of planting and harvesting time.)

  1. Prevailing market prices and profit margins.

In some crops harvesting can be delayed to wait for better prices. This makes one to realise higher profit margins.  E.g. in carrots and pears.

Methods of harvesting.

Crop.  Method of harvesting. 
Coffee. Ripe berries are picked and put in bags ready for pulping in the factory.
Tea. Two young leaves and a terminal bud are plucked and put in airy baskets to prevent fermentation.
Irish potatoes. Tubers are lifted using sticks, panga, or forked jembe.
Beans. Green pods are picked for the market.  Dry beans the whole plant is uprooted after drying, spread on mats to dry further, threshed and winnowed.

Precautions during harvesting.

Harvest when it is dry to prevent rotting of produce.

Delayed harvesting should be discouraged as some crops get spoilt in the farm.


Practices carried out on the crop after harvesting.

  1. Threshing

Act of removing maize grains from cobs, beans from pods, sorghum from the heads.


Facilitate cleaning and subsequent storage.

  1. Drying

Prevents rotting and fungal attack of the stored produce. Maize is dried to a moisture content of 13%.

  1. Cleaning

Winnowing in cereals and pulses to remove chaff from the grains. It increases quality of the produce by removing foreign materials.

  1. Sorting and grading.

The produce should be sorted and graded according to quality and size.

  1. Dusting

Applying chemical powder on seeds to prevent attack by storage pests.

  1. Processing

Transformation of raw materials into final products.

Reasons for processing.

  1. Improves flavour of the produce in tea and tobacco.
  2. Improves keeping quality in fruits when canned or made into juices or sauces.
  3. Reduces bulkiness in order to lower transportation and storage cost e.g. in sugar-cane.
  1. Packaging.

Placement of produce into containers for storage, sale or transportation.


Reduces damage to the produce.

Makes it easier for the farmer to quantify the produce and set prices.



It ensures availability of the products throughout the year.  Agricultural produce are perishable and thus require to be prepared before they are stored.

Types of storage.

Ideal storage structures should be:

  • Water-proof/leak proof. Ø Rodent free.

 Traditional storage structures.

They are elevated from the ground by posts. Their walls are roofed with thatch materials such as grass, reed etc.


  1. Rat and weevil attack.
  2. Rotting of grains.
  3. Limited in size.

  Modern storage structures. 

Involves improving the storage conditions of produce to prevent losses.

Characteristics of a good grain store.

  • Rat/vermin proof.
  • Well ventilated.
  • Easy to load and offload.
  • Pest free.
  • Leak proof.
  • Well secured to minimise theft.
  • Cool conditions to minimise overheating of grains that would lead to cracking of grains.

Preparation of the store.

  1. Cleaning the store.

The store should be cleaned thoroughly removing all debris of previous crop that might harbour storage pest.

  1. Maintainance

Broken and worn out parts should be repaired or replaced to ensure security of produce.

Ensure the store is leak proof.

  1. Dusting

Using appropriate chemicals to control storage pests

  1. Clearing vegetation around the store. To help keep off vermin from the store.