Nitrogen-fixing 'fertilizer trees' have long been used by farmers in farming-difficult areas such as parts of the Sahel. Rainfall is poor, the soils are often sandy and infertile, and yet there are several varieties of acacia and other nitrogen-fixing trees which do well there.
That these trees benefit other crops growing under or between them has long been known. What is perhaps fairly new in recent years is the more scientific study of the phenomenon, and its deliberate encouragement in parts of Africa that have not previously widely used these trees as an additional soil fertility supplementation strategy.
Given all this, 'Can Integration of Legume Trees Increase Yield Stability in Rainfed Maize Cropping Systems in Southern Africa?' seems like a somewhat superflous question whose answer is already known.
Nevertheless, researchers at the World Agroforestry Centre (ICRAF) have been undertaking a 12 year study to find answers to the question. The 'hook' they used to justify the study and give the impression of finding something new was that they were studying the 'stability' of the yields of maize intercropped with Gliricidia sepium.
Amongst the findings:
* the control fields of conventional (inorganic fertilizer-using) maize monocultures had the highest
* close behind were the yields for maize intercropped with Gliricidia sepium and then supplemented with 50% of the inorganic fertilizer that would normally be used in 'conventional' maize monocultures.
This is an interesting practice long used by 'resource poor' farmers-using 'agro-ecological' farming techniques to stretch out and supplement the relatively small amounts of inorganic fertilizers they can afford to buy. This is real world small holder farming, not the pie-in-the-sky 'fully organic or death' mantras mouthed by activists in cushy donor-funded offices in town, worlds away from the realities of scratching out a living from the land..
The study's conclusion: "Maize yields remain more stable in maize–gliricidia intercropping than in fertilized maize monoculture in the long term, although average yields may be higher with full fertilization."
Hardly a ground-breaking study or findings, but still interesting.
African Agriculture
The lucrative tree farming industry is being threatened by a deadly bacterial wilt that has been discovered by Ugandan scientists. The wilt is mainly affecting pine trees - the species that tree farmers most commonly investing in.
Dr Grace Nakabonge from the department of Forest Biology and Ecosystems Management, Faculty of Forestry and Nature Conservation, Makerere University, in an open forum held in Kampala on the theme ‘Biotechnology Research and development in the forest sector’, explained that they were alerted about the problem by farmers from Nakasongola last year.
Scientists are now carrying out a country-wide survey on tree planting and forest conservation to determine the extent of the problem. However, while carrying out this survey, the team discovered that the pine tree species were not only withering in Nakasongola pine plantations, but in pine farms throughout the country.
Pine is grown in the districts of Kabale, Lira, and Busoga region among others. Farmers in Uganda took to pine farming because the trees do not take long to grow, and they have a high demand in the wood industry because they produce good timber.
Dr Nakabonge said the wilt attacks the roots of the trees in the soil and eventually causes them to dry. She said Uganda is not the first country to experience such bacterial wilt attacks on the pine species. South Africa, which is the biggest pine growing country, is facing the same problem.
Scientists in the forestry department at Makerere have sent samples of the infected pine trees to a laboratory at Pretoria University, South Africa, to establish the identity of the deadly bacteria wilt which is destroying these trees.
“Farmers who plant the pine tree on their farms have never experienced this type of bacterial wilt because this is the first incidence of it, but we shall find a method for its eradication. However, in my opinino, the farmers should not give up in their planting projects for this tree species because, with good farm management the trees can always survive,” Nakabonge said.
She said that due to the effect of the climate change, various diseases, pests and other bacterial wilts have emerged and are attacking tree species including the natural trees in our forests.
However, she said that there is need for farmers to adapt to using some hybrid tree species, since the world forest-cover is declining very fast due to demand for the product for energy purposes.
A farmer specializing in growing pine in Ogengo Village, Lira district, Ms Janet Akibua, is one of those whose trees were attacked by the wilt. However, she mistakenly attributed it to the dry weather despite having planted them during rainy season.
According to her, she planted about 1,500 trees last year in October, but after one month many of them began dying, leaving less than 1,000 surviving now. A survey carried out by forest conservation scientists indicates that most Ugandans depend on biomas as a source of energy. They are calling upon the nation’s farmers to establish forest plantations in highly productive tree species such as eucalyptus and pulp which are used in developed countries to manufacture paper.
The Natural Agricultural Forest Research Resources Institute (NAFORI) in Kifu, Mukono, is currently multiplying seedlings of hybrid eucalyptus imported from South Africa and selling them to farmers.
The Commissioner of Forest Sector Support, Ministry of Water and Environment, Ms Rachel Musoke, called upon government to invest more money in research to train more personnel in tree breeding so that quick solutions can be worked out to safeguard the tree species from the emerging wilts. She said that deforestation occurs because the forestry sector is underfunded and few people are sensitized about the dangers of cutting trees and not replacing them.
“In Uganda, 15% of the forest is under National Forest Authority, 15% is under Uganda Wildlife Authority, 69% is allocated to the District Forest Services and 1% to the communities, but no fund is allocated for the latter two,” she said. “This is why 50,000 hectares of forest estate are lost every year.”