Importance of timely harvesting in reducing post maturity losses

By Bob Aston

Farmers have been urged to ensure timely harvesting in order to minimize post maturity losses in the field. Speaking during a workshop organized by Agricultural Sector Development Support Programme (ASDSP) for members of Laikipia Produce and Marketing Co-operative Society at Ng’arua Maarifa Centre, Laikipia West Sub County on May 26, 2015, Mr. James Kamau, Ol-Moran Ward Agriculture Officer said that maize should be harvested at the right stage depending on the intended use.

“Although time of harvesting fall under pre harvesting period, its effect has direct linkage to post harvest challenges. During harvesting, care should be taken to make sure that the produce is not affected in quality or quantity,” said Mr. Kamau.

Dry maize ready for harvesting

He said that physiological characteristics for mature maize include: yellowing of most of the leaves; leaves drying up; yellowing and drying up of the husks; maize cobs begin to droop on the stalk; maize grains acquire a shiny surface; grains becomes too hard and uncomfortable to chew when it is roasted for eating; and black layer develops at the base of grains.

“Maize harvesting should start once the maize attains its physiological maturity. This is usually between 90-180 days depending on the variety and agro-ecological zone,” said Mr. Kamau.

Delayed harvesting after physiological maturity increases chances of storage pest infestation, shattering, damage by birds, wild animals and losses due to theft, thus reducing the quality and quantity available for consumption and sale. Delayed harvesting may also cause a problem as the fields need to be prepared for the next crop.

Harvesting should be timed to coincide with dry weather as wet harvesting enhances rotting of produce. During the wet season break the stem just below the cob and hang it downwards to prevent water entry into the cob. Use of maize varieties with ear rot resistance, ear dropping traits and closed husk cover is also recommended to reduce maize ear rot.

Stooked maize in field

“Early harvesting as soon as the crop reaches physiological maturity will be heavier than if left in the field to dry longer. This results in significant damage to the grain and makes it more difficult to market commercially,” said Mr. Kamau.

Method of harvesting

Cut the maize stalks and stack them in pyramid-shaped heaps (stooking). At this time the grain moisture content is around 26%. Stooking is important before ears are removed from the stalks to allow sun and air to dry the cobs for easier dehusking. Stook maize for two or more weeks to dry in the field (grain moisture will reduce to 18%).

Ensure that stooked maize does not overstay in the field because of theft cases. In such cases, stack the cut stalks in pyramids near your house. After the maize has dried, remove the ears from the stalks and dehusk the ears manually

During harvesting, avoid dropping of dehusked cobs on the bare ground because it increases the chances of fungal/Aflatoxin contamination. Dehusked cobs should be placed in clean containers, mats, tarpaulins or directly into bags to avoid contamination. Separate clean maize from rotten or pest infested cobs. Make good arrangements of transporting clean cobs from the field to the store.