Environment Theme

Crop survival in a hot climate

Climatic uncertainties: A farmer applying fertiliser to his rice fields in Medak district, some

60km from Hyderabad. Monsoon rains in India this season (June to September) has been

35% below average, causing rice planting to be 18% lower than for the same period last year.

Climatic changes are affecting food cultivation worldwide. – AFP

In a world that is warming too fast, farming methods will have to change.

CHANGES in temperature, precipitation and wind patterns that are associated with climate

change are expected to affect crop production – hence, food security is a looming issue.

Global warming is projected to alter the production of rice, wheat, corn, soybean, and

potatoes – diet staples for billions of people around the world. Which is why agronomist Dr

Ajit Singh contends that it warrants global concern?

“Food crops that we rely on most are sensitive to climate change as not only are the

temperature and moisture of the surroundings affected, but those in the soil too. Simulation

studies project a 20% and 30% decrease in global crop production, attributed to climate

change, by 2020 and 2030,” says the associate professor at the School of Biosciences at

University of Nottingham Malaysia Campus at a talk titled “Effects of Climate Change on

Food Crop Production”.

“The growth stage is important as the crop will be exposed to drought or heat. Flowering or

fruiting can be extremely sensitive, and the temperature and rainfall changes induced by

climate change will interact with atmospheric gases, fertilisers and soil organic matter to

produce unanticipated responses,” he says.

Climate change will alter the production of major food crops, according to Dr Ajit Singh of

the University of Nottingham Malaysia Campus.

To illustrate how climate change correlates with crop output, Dr Ajit shares data from studies

in three different regions: the African arid climate in Niger Republic, the semi-arid climate in

Sokoto, Nigeria, and the tropics in Alor Star, Kedah. Based on data from the Meteorological

Centre in Niamey, the Niger Republic – which has an annual rainfall of less than 500mm –

recorded no significant increase in temperature between 2003 and 2012. Complete data on

crop production could not be obtained but it showed mixed responses to temperature changes.

“The lack of data meant that we could not arrive at a conclusion but it gave us an idea on the

kind of crops that are resilient or not affected by temperature increases. We found the hungry

rice (Digeteria exilis) and groundnuts to be more resistant. This will prove useful when it

comes to selection of crops in future.”

In the semi-arid climate of Nigeria where the annual rainfall is between 600mm and 800mm,

20 years of data from the Energy Research Centre in Usmanu Danfodiyo University in

Sokoto showed an annual average increase of 0.04°C from 1991 to 2001. Rainfall remained

unchanged during that period. Crops like onions, tomatoes and peppers were found to be

suitable for the dry season when temperatures were lower while rain-fed groundnuts appeared

to be more resilient.

“In Alor Star, Kedah, 30 years of data gathered between 1981 and 2010 showed an annual

average increase in temperature of 0.03°C. If we assume that there were no significant

changes in rice production from either agricultural technology or a newly-introduced variety

during this period, the linear trend analysis between temperature and rice yield demonstrated

a positive response to the increase in temperature during this period,” says Dr Ajit.

He says there are various agricultural practices to offset the adverse effects of climate change

on crop production and soil, such as mulching, that will help with water conservation and soil

fertility, and crop rotation, which contributes to sustainable cultivation.

“Crop rotation or inter-cropping is an effective, natural pest control method since increased

pest attacks are likely to arise from insects that reproduce from a lengthened breeding season

and which multiply and thrive in hotter temperatures,” he explains. He adds, however, that

mono-cropping (growing the same single crop every season) is commonly practised in

Malaysia and other parts of developing Asia because of profitability in the short term.

Cultivation of papaya, pineapple and oil palm are examples of mono-cropping systems.

“Continuous cropping of the same plant results in accumulation of pests and diseases that are

difficult to control. The organisms causing the disease are host-specific, that is, they survive

on one plant only. If another plant is cropped the following year or after five to six years in

rotation, the pests eventually die because they cannot survive on the new host. Crop rotation

and inter-cropping were practised in the past but farmers nowadays do mono-cropping using

high-value crops to reap more profits.”

As ridding pests by using chemical pesticides will add to carbon emissions, Dr Ajit says

organic control should be advocated. He explains that although carbon dioxide is an essential

compound in photosynthesis which also increases water-use efficiency in plants, these

positive effects of the gas can be nullified by related increases in moisture stress caused by

low rainfall and high temperature. Also, increased cloud cover due to higher global

temperature is projected to limit the photosynthesis process and result in decreased crop

production.

Dr Ajit says other ways that farmers can mitigate the effects of climate change on crops is to

improve crop varieties to ensure a diversity of plants, and to conserve germplasm.

“With rising incidences of drought, water-use efficiency has to be optimised. Crop condition,

too, has to be monitored, especially with the presence of weeds which are better-adapted to

arid conditions than crops, and which will lead to increased competition for moisture,

nutrients, and light.”

For food security to be guaranteed, he says people must improve the way they manage

agricultural systems. As most models observe climate change on a global scale, a customised,

local model variation will be needed for people to come up with adaptation measures in

Malaysia. The Food and Agriculture Organisation has urged for a shift to climate-smart

agriculture. Various crops are being planted in different regions. One example is the agro-

forestry system in 120,000ha on the slopes of Mount Kilimanjaro, Tanzania, where coffee is

grown in between forest trees.

In Peru, 3,500 families are helping to conserve 177 varieties of potatoes (an essential food

crop for Peruvians) to protect genetic diversity. In Nigeria, farmers bury urea briquettes in

rice fields, which raised yields by 25% as well as reduced nitrogen release by 40% and usage

of urea by 25%. The technique also prevented loss of fertiliser through surface runoff