Here is how to grow carrots in saline soils

Hundreds of carrot plants stand in beautiful rows on the farm off Namanga Road in Isinya, Kajiado County.

Their lush green leaves sway as the wind blows gently from the nearby plains. Walking on the five-acre farm owned by Anderson Samperu evaluating the plant’s growth rate, development, size, shape as well as the amount of vegetation they contain are three experts.

“In about a month’s time, they will be much bigger and evenly sized than they are at the moment,” says Eric van Zandwijk, the project manager at Delphy, a Dutch organisation that specialises on plant cultivation.
With him on the farm is Rogier van Opstal, a hydrologist and water management expert from Nectaerra, and Bas Bruning, an ecologist and saline agriculture expert at Salt Farm Texel. Both organisations are based in the Netherlands.

Ground-breaking research
The trio are engaged in a ground-breaking research in which they are growing carrots in saline soil.

“About a third of Kenya’s soils are saline, which means certain crops, including carrots, hardly do well in various areas. However, there are conditions that if observed, a farmer gets 100 per cent harvest in the saline environment,” says Bruning.
Salinisation, according to him, can take place anywhere, but dry to moderately dry areas are more prone to the problem.

Normally, as salinisation of soil and water increases, crop yields decrease to the point that the land can no longer be used for food production.
According to Bruning, salinisation is partly caused by man through using wrong irrigation methods.

“This happens when people use saline water for irrigation. When the water quickly evaporates, it leaves the salt behind, which accumulates over time eventually causing the negative saline effects.

The saline agriculture expert further states that climate change is also worsening the salinisation problem globally due to extreme precipitation in some areas causing saline groundwater to rise. This is heightened by rising sea levels.

“Salinity can also be caused by displacement of oceanic salt, carried by wind and dumped through rains in arable lands. The presence of salts in the soil reduces the ability of the plant to take up water, which leads to reduction in growth rate,” offers Bruning.

Effects of salinity to crops

Once excess salt enters the plant in the transpiration stream, there will be damage to the crop’s cells in the transpiring leaves, inhibiting growth, he adds. The best way to curb the problem, according to him, is for the farmer to focus solely on reducing salt concentration in the soil through use of saline agriculture.

“The first step is to stabilise the soils’ salt concentration and keep it constant. This is achieved through the use of good drainage systems and smart irrigation in determinate rates — in terms of both water amount and method of application. The crops should ideally be watered at the root, and not on the leaf,” he says.

The farmer should also choose the right varieties of the crop to grow for the prevailing salty ecological conditions. The soil’s salt level and water determines the choice of variety.

The carrot varieties grown at Samperu’s farm, which include Nantes, are for saline conditions. Two other varieties under research have been developed in the Netherlands.

Other crops on the five-acre farm are French beans, onions, a variety of vegetables and maize.

Practices such as mulching, proper irrigation and drainage, and agroforestry near the farm, further helps in effectively cultivating crops in saline conditions, according to Opstal.
“Mulching helps in reducing evaporation thus keep sthe salinity of the soil constant. Crops protected with mulch hardly require frequent watering. And water used for irrigation, in most cases, has some amount of salt in it,” he says.

Agroforestry

Opstal advises that agroforestry as well as planting crops such as bananas near the farm helps to reduce the level of wind-caused evaporation, as well as keeps the dampness underneath constant since rapid evaporation is one of the things causing salinity.

“In saline conditions, soil moisture has to remain constant. The farmer, however, has to be vigilant and always look out for fungal infections caused by the constant dampness, in the crops,” notes Zandwijk, adding that whenever the soil and water used for farming are saline, yields tend to be adversely affected.

For good carrot cultivation in saline conditions, Bruning offers that one should start with measuring the salinity of the soil and ensuring that the soil is fine, not coarse. “Coarse soils lead to uneven and malformed carrots which are not good for the markets,” he says.

Testing of the soils, he explains, involves collecting samples from different sections of the farm and it should be done at least three to four times per year.

Rain and precipitation in an area sometimes tend to influence the results of the tests as the rainwater attenuates the intensity of the salinity.
However, when it evaporates, the soil retains intense salinity, which is why it is imperative to carry out several tests, and consider the weather elements, he says.