Potatoes are a staple food for a large segment of Kenya’s population and it is important because it is rich in carbohydrates. Potatoes have a life cycle of about three and a half months, making it sometimes possible to produce two crops of potatoes in a year.
Taking into account the production seasons in different producing regions, the production and marketing of potatoes should be planned such that potato supplies to markets are constant and evened out so as to ensure constant flow throughout the year.
The high fluctuations in availability and prices from season to season and within seasons are one of the greatest problems in the production and marketing of potatoes.
Determining soil pH is the primary step that should be undertaken at the site selection stage. The pH value of soil defines the concentration of hydrogen ions present in the soil solution. Fortunately, potatoes can be grown successfully in soils with pH values as low as 5.5 or lower. Caution is required as very low pH values can induce magnesium deficiency and also the fore mentioned aluminum toxicity.
The land should be prepared early before the onset of rain to avoid soil compaction. Preparing the land when it is not wet allows for increased aeration, free drainage, destruction of weeds and decomposition of other crop residues. Potato roots and tubers need loose soils that have adequate air supply and are well-drained to produce good yields. Compacted soils or water-logged soils have poor air supply and lead to poor yields. Plough the soil to loosen it and reduce the soil resistance to root penetration and tuber development.
The following are the steps and methods for land preparation;
Step 1: Vegetation Clearing.
The first step is to slash bushes and weeds. Remove and destroy volunteer potato plants if any. The trash residues can be placed on the contours as trash lines.
Step 2: Ploughing.
Plough the land at least 3 weeks before planting. This should be done to a depth of 25cm when using a disc plough and 15 cm when using hand hoes. If the land is virgin, it is recommended that 2 ploughing should be done at an interval of 1 week but if it is cultivated land, 1 ploughing is sufficient.
Step 3: Harrowing.
Harrow the ploughed land one week later to allow better soil working conditions. Carry out at least two harrowing passes, with the last one being done just before preparing of furrows or ridges so as to destroy young weeds for virgin land but for cultivated land 1 harrowing is sufficient.
Step 4: Levelling.
Leveling is done to allow equal surface water distribution. Using hand hoes, level the land by moving soil into depressed surfaces along the contour. When using a tractor, run a harrow along the contours to achieve a flat site.
Planting should coincide with the start of the rains so as to maximize water utilization. There exists different recommendation on planting potatoes which include: planting on ridges or furrows, spacing, manure and fertilizer use, amount of seed needed and depth of cover. The seed should be planted with the sprouts facing up whether in ridges or in furrows.
- Potatoes grow mostly on loose loamy soils or sandy loam soils which require frequent rainfall/ irrigation.
- Use of certified seed, free from weeds and pests is recommended in order to boost production.
- Plant in beds with the correct tilth to allow good and even multiplication of tubers.
- Accurate planting in the correct tilth to ensure good and uniform multiplication of the potatoes.
- Ploughing gives the potato bed consistent tilth and good aeration to encourage the potato tubers to multiply sideways.
- Potato tubers should always have a soil cover and never see light. Light stops its multiplication.
- Soil cover should be done 2-3 times during the growth cycle.
- Weeds need to be removed as soon as they germinate in order to curb yield losses associated with their presence.
- Control pests and diseases like potato blight by spaying – preventive spraying.
Maintaining and Improving Soil Fertility
Soil fertility in a potato farm can be improved and maintained through interventions such as:
- Application of mulches.
- Application of Bio-fertilizer (compost)
- Application of Farm Yard Manure (FYM)
- Application of Green manure.
- Application of Plant tea/ Liquid manure.
- Soil conservation measures.
- Planting of Nitrogen-fixing plants like legumes.
- Practicing crop rotation and other recommended cultural practices.
- Use of inorganic fertilizers.
- Avoid manure from livestock fed with potato /Solanaceae crop residues.
- Organic fertilizers should not be made using potato crop residue.
Crop rotation is an important agricultural practice in potato production because it helps in managing the build-up of pests and diseases associated with potatoes and other crops from the Solanaceae family. Adoption of suitable rotation plans cuts down on the spread of potato pests and diseases between crop seasons. Grow potatoes only on virgin or fallow land or land where potatoes and other Solanaceous crops have not been grown in the previous seasons. Also, avoid land where volunteer plants from these crops are present since these crops usually act as an alternate host for most potato pests and diseases.
Consider your target yield when considering the nutrient application rate. For instance, producing 56 tons/Ha potatoes require about 235 kg N/Ha, 31 kg P/Ha and 336 kg K/Ha. Potato is a heavy feeder of K (potassium) which DAP does not have because it contains only nitrogen and phosphorus; DAP has too much P (phosphorus) which could cause long-term acidity if used for a long time.
It is advisable to split N (nitrogen) applications during the lifetime of a crop because losses of N occur much faster and cannot survive until crop maturity.
Potato harvesting can be done by hand or through mechanized harvesting. Losses can be incurred/caused by cuts as a result of manual harvesting mechanisms. This can be minimized by using quality and proven equipment i.e potato harvesters which lift the potatoes and the soil just below the crop and the soil is sieved as it passes through. Undamaged potatoes are then dropped back on the soil surface to be weather hardened and then bagged for marketing.
The following should be considered during harvesting;
• Harvest when the soil is dry.
• Harvest when it is relatively cool with cloud overcasts.
• Do not expose harvested tubers to sunlight for a long time so as to prevent them from drying out too quickly and avoid greening of the white skin varieties, which would reduce their keeping quality and consumer acceptance.
• Avoid harvesting when the soils are wet in order to avoid pathogens sticking on tubers.
• Shield harvested tubers from rain to avoid the risk of rotting.
Prepare a marketing strategy before embarking on potato production. The market assessment should include:
• Annual price trends at the farm level, aggregation (broker) level and at wholesale
• Market players (aggregators, transporters, wholesalers, retailers, consumers and market
managers) and their roles.
• The customer behavior and preferences in terms of variety preference, amounts demanded, the quality required, payment modes among others.
• Cost-benefit ratios of marketing own produce versus selling through brokers.
• Identify competitors (other farmers) including an assessment of their strengths and