Greenhouse farmers loose yields to ignorance

greenhouseLack of requisite information on greenhouse farming and management is turning against majority of farmers who rush into the promising venture buoyed by the good returns, with failure to observe simple greehouse rules like sheeting now costing them upto half of their yields.

Yield losses, which should be minimal in greenhouses are now going upto 50 percent of entire harvest, in what is attributed to avoidable circumstances like lack of clear information on the operations of greenhouses.

Utilization of new knowledge and productivity enhancing innovations has been fronted by policy makers in Agricultural sector as the key for transforming small holder agriculture from subsistence to commercial enterprises and for that case, farmers have been sacrificing the little earnings they have to acquire the greenhouses as a high tech kind of farming which guarantees success.

Over 60 percent of greenhouse tomato farmers In Embu and Kirinyaga counties have been getting even lower yields than their open field counterparts despite investing in the costly greenhouses. “Most farmers adopt greenhouse farming based on recommendations from friends, and after witnessing marketing content that greenhouse supplying companies carry out online or on television and therefore adopting the method without prior knowledge of the technology. This therefore explains the many problems like bacterial wilt, insect pests among others that are associated with open field farming being experienced in the greenhouses and consequently curtailing the would be increased yields that motivate farmers into the adoption of the technology,” explained Dr. Jesca Mbaka  Head of Crop Protection Unit at Kenya Agricultural Research Institute (KARI) Thika.

Some of the affected farmers have been seeking help from KARI Thika, “In a week I could record over 10 cases of almost similar nature most of which were undertaking greenhouse vegetable farming. For instance a tomato plant would produce less than 7kgs and yet under optimal conditions in a greenhouse it should produce over 20kgs,” noted Dr. Mbaka.

The numerous cases she received from frustrated greenhouse tomato farmers prompted her and five other scientists from three other institutions with funding from the National Commission for Science and Technology (NCST) to invest in tracking the root cause.  The two year project which initially focused on the major tomato growing areas of Embu and Kirinyaga Counties brought to the light the ignorance by most of these farmers coupled with poor designs from the manufacturers whose interest is economic gains from the sales they record. “We discovered that many greenhouse tomato farmers were still struggling with bacterial wilt, poor hygiene, pests and poor structures which all combined contribute to reduced yields by upto 50 percent and exposing the farmers to more losses compared to the open field farming,” noted Dr. Mbaka. She also explained that, the disappointments that the farmers are encountering explain why the early adopters are abandoning the technology and rate of abandonment has been on the rise with estimates close to over 10 percent annually.

“A visit to the farmers on the ground brought to the limelight the greenhouse management problems like poor hygiene, aeration, soil preparation, choice of a good design among others that farmers were grappling with. The farmers are sold the greenhouses with little or no knowledge on how to manage them,” she said. For farmers to realise the benefits of this technology, the scientists decided to enlighten them on the management of greenhouses. The choice of the right greenhouse sets a farmer rolling either towards success or failure. There are various design structures being retailed to farmers and although some of them cost a fortune they do not guarantee success.  A good greenhouse should be tailor made to comply with a region’s climatic conditions and capable of being regulated to the area's climatic conditions.

Dr. Mbaka also recommends a structure that has double door entry points with the small room between the two entry points having feet cleaning point to deter the transfer of bacteria and other pests from the mud of the feet of the people entering the greenhouse.   The farmer also uses this room to deter pests from the open field and also conduct a body check to ensure that he has no pests like white flies on his clothes before entering the main farming point. Bacterial wilt one of the most endemic diseases in greenhouses infects tomatoes and other horticultural crops, with the plant wilting and is responsible for over 90 percent of yield losses.

Whiteflies another horticultural crops meance have piercing-sucking mouthparts which they use to tap into the plants vascular tissue and steal all the nutrients being transported hence causing deformation of developing buds, wilting and chlorotic leaves. Whiteflies can also transmit some plant viruses and it is recommended that if a farmer's plant gets infected with a virus, they should uproot it. Whiteflies, also like aphids, secrete honeydew, causing the opportunity for sooty mold to grow. Feeding by whiteflies can also cause deformed fruit and discoloration of your tomatoes.

She therefore warns that these pests are dangerous and if a greenhouse is not well built to deter them, then the farmer can experience a total loss as their control through pesticide is expensive and also needs immediate response before the whole plantation is affected.

Solarization is another process that the scientist advised farmers adopting greenhouse tomato farming to embrace in order to realise the gains they yearn for. Solarization is a non pesticidal method of controlling soil borne pests by placing plastic transparent sheets on moist soil during periods of high ambient temperature for at least eight weeks.  For better results, the soil surface inside the greenhouse should be leveled and irrigated before being covered with plastic sheeting.

The plastic sheets allow the sun's radiant energy to be trapped in the soil, heating the upper levels. Solarization according to Dr Mbaka should be done during the hot season months in order to increase soil temperature to levels that kill many disease-causing organisms, nematodes, weed seed and seedlings. In addition, the process leaves no toxic residues and can be easily used on also open field for small or large scale farmers.

Soil solarization also improves soil structure and increases the availability of nitrogen and other essential plant nutrients through speeding up the breakdown of organic material in the soil, which results in the release of soluble nutrients. Adoption of this process will guarantee a farmer threefold yield in greenhouse and also save over 50 percent on the money used to buy pesticides and labour as there will be reduced pests and weeds. “Improved hygiene and solarization reduced by half the amount of pesticide that I used because the spraying intervals were longer as there were reduced cases of pests and diseases. In fact, I never witnessed any wilting of my plants meaning that the solarization process eliminated the bacterial wilt in the soil,” explained Mashaki Joshua a farmer in Mbeere and a beneficiary of the training by the team led by Dr. Jesca Mbaka.

Greenhouse tomato farmers were also encouraged to practice crop rotation to avoid disease build up. “When rotating from tomatoes, one should switch to any other crop apart from green pepper which also habour same pests and disease traits like tomatoes,” noted Dr. Mbaka. The scientists’ sensitization training program is yielding better returns as some of the beneficiaries are reporting success. “Anybody who follows our instructions on greenhouse tomato farming has registered triple yields as one plant that initially could produce 8kgs registered an increase to 20-30kgs which is the recommended yields under all these optimum conditions in the greenhouse,” noted Dr. Mbaka.

Her claim is backed by Raphael Ngari a beneficiary farmer from Embu, “I gained from the KARI scientist’s training and am now equipped with full knowledge of greenhouse production right from the land preparation, plant nutrition to postharvest handling. In addition, I harvested over 8000kgs of tomatoes from my 30 by 6 meters greenhouse and sold it at an average of Sh60 per kg translating to over half a million in a single season,” Ngari explained.


For more information on the greenhouse management and training you can contact Dr.  Dr. Jesca Mbaka on 0722882422

Or email her on This email address is being protected from spambots. You need JavaScript enabled to view it.