Saturday, 19 October 2013
Friday, 18 October 2013
Mother Earth News
By Sam Glenn Griffith
You can find a bargain in the pool of available small farm tractors, but be sure to put the vehicle through its paces before making a purchase.
The best source of information about small farm tractors for the first-time buyer (a source which, for some reason or other, most such people ignore) are the very farmers in your area who are already raising the kind of crops you aim to grow. So, when you're faced with the need to purchase one of the expensive implements, begin the search by visiting your neighbors.
Note the make and size of the tractors they're using, and ask for evaluations of the machines. (A pleased owner will often be fiercely loyal to his or her "pet" brand, but someone who feels that he or she has been sold a "lemon" will likely fill your ear with all sorts of horror stories. Use a little common sense when weighing extreme opinions and you'll learn a lot.) Ask, too, about the attachments each farmer owns in order to learn which accessories were a waste of money and which he or she wishes had been bought but weren't.
Working farmers can tell you a lot about tractor dealerships, too. The quality of the dealer is every bit as important as is that of the machine itself! Try to determine which sales outlets have good stocks of parts and reputations for quick service. I once had a tractor broken down for two full days—at the height of my busy season — because the dealer didn't have a two-cent packing washer for the machine's hydraulic system.
In fact, it's a good idea to buy a brand of tractor that's supported by two dealerships within a few hours' drive of your home. Then, if the closer establishment can't supply a part you need, you may still be able to keep your machine up and running by going to the other dealer in search of the required part.
A Tractor Field Guide
You may well be surprised to know that it's possible to buy a small farm tractor that's specifically designed to handle just about any task you can imagine. However, the two most common tractor types — and those that'll most likely satisfy the needs of the new farmer — are the utility tractors and the general purpose (also called "row crop") tractors.
Utility tractors are typically low and squat-looking. (A common example, in the lower price ranges, would be one of the Ford 8-N's manufactured in the 1950's.) Utility tractors are designed for pulling and powering implements — such as hay mowers, balers, disk harrows, and trailers — that are attached to either a hitch or a lifting mechanism at the rear of the tractor.
If you don't intend to do any multi-acre rowcrop farming, a utility tractor can be a good investment. However, even though the machines can be used for plowing and cultivating fields, they certainly don't make such jobs easy. The towed-behind attachments necessary to tend row crops with a utility tractor will force you to drive with one eye on the cultivators (for instance) and the other on the row ahead. You'll find that such a setup will sometimes cause you to plow up more peas than weeds ... and give you a backache, to boot.
The general-purpose tractor, on the other hand, can perform almost every job that a utility machine is capable of tackling, yet it's designed to care for row crops. Such tractors have greater ground clearance than do the utility models, a feature that allows them to straddle rows of crops — while cultivating the field — without disturbing the plants beneath them. General purpose tractors also usually carry their attachments between the front and rear wheels, and frequently have their engines set off slightly to the left ... allowing a driver to look down and make sure the cultivator or other implement is exactly where he or she wants it.
In addition, the distances between the left and right wheels of row-croppers can often be adjusted, allowing the machines to be used to tend crops that require a variety of row width settings and enabling you to get the maximum use out of your property and your tractor.
General-purpose tractors are either single-row or multiple-row (the latter are always designated in even numbers) machines. The one-row models, of course, are smaller and usually have the front pair of wheels in line with the rear set. Multiple-row tractors sometimes use a "tricycle" arrangement in which the front tires are placed close together. The larger machines can make short work of big level fields but are also relatively cumbersome and difficult to maneuver, while the tricycle wheel arrangement is somewhat less stable than is the "four-square" pattern common on single-row models.
A Few Farming Fuels
Almost all tractors available today are powered by either gasoline or diesel engines. (You will occasionally see tractors for sale that are fueled by LP — liquid propane — gas, often at very low prices. But unless you can be sure such machines are in prime condition, be wary of them. Parts are scarce, and, after buying one, you could well find yourself stuck with an inoperative "classic.")
The engine in a gasoline-fueled tractor is essentially the same as those found in most automobiles, but the farm implement's powerplant will likely run at a lower RPM and produce more torque per unit of displacement than will an auto engine. Most tractors have relatively low horsepower ratings, too. Don't be misled by this fact: A 20- to 30-HP machine will be more than adequate to handle the chores demanded by a family farm.
A diesel-engined tractor has both advantages and disadvantages as compared to gasoline-powered machines. For one thing, since a diesel engine is "fired" by the buildup in engine compression caused by the movement of the pistons, it doesn't require the points, distributor, and spark plugs—nor the adjustment and/ or replacement of such parts—necessary to a gasoline powerplant.
And, though diesel tractors usually cost more initially than do comparable gasoline-fueled machines, they're less expensive to operate. Diesel oil is still not as costly as is gasoline, and tractors powered by the "bargain" fuel tend to get more work done per gallon than do their gasoline-engined counterparts. Finally, a typical diesel tractor will both outpull and—if carefully maintained, with special attention paid to regular cleaning and replacement of the air, oil, and fuel filters— outlast a gas-powered machine of the same size.
Perhaps the single most annoying drawback of diesel-fueled tractors is their tendency to be difficult to start on cold mornings. Since they're fired by the heat built up by compression in the engine, a good bit of battery power is required to turn the pistons long enough to get a start in cold weather. And, of course, chilly temperatures tend to drain battery power ... in effect adding insult to injury.
However, newer diesels often feature "glow" or heat plugs, which, at the flip of a switch, start to warm the cylinders. After a minute or so of such priming, the engine can usually be cranked and fired with much less difficulty than would otherwise be encountered. Furthermore, heat plugs can be installed on diesel tractors that don't come equipped with them.
The power takeoff unit — the "business end" of which is a splined shaft running from the back of the tractor's differential — is used to power such attachments as hay balers and mowers. The PTO will run off the differential or the engine itself, and is engaged by a combination of its own lever and the tractor's clutch.
There are two types of PTO: "standard" and "live." The latter is generally considered more versatile, since it can be operated while the tractor isn't moving as a result of the clutch's being disengaged ... while a standard unit will work only while the machine is in motion — or in neutral — with the clutch engaged. Therefore when, for example, a "live PTO" tractor's hay baler encounters a large stack of to-be-bound fodder, the operator can, on some models, simply press the clutch in halfway ... bringing the tractor to a stop while the baler handles the pile of hay. With either type of system, the PTO should work when it's engaged, and stop completely when disengaged. If the shaft continues to rotate slowly after disengagement, you can bet that the PTO gear is worn and will require a (probably costly) repair job!
A "Lifting" Experience
Another feature that should be checked before making a purchase is the tractor's lifting system, which will be either a spring (In older, mostly pre-1950, models) or a pump-driven hydraulic system.
If your chosen machine is of the latter type, go over the system very carefully for leaks and beware of any tractor that shows a lot of hydraulic-fluid seepage (the liquid will be a very light, about 10-weight, oil). Before laying your good money down, give the lift a try, too. Hitch a heavy implement to it, then push the lever that operates the lift. If the unit jerks, slips, or wheezes while raising its burden, it may be low on oil (which could be a sign of a leak or of less-than-perfect maintenance). Should the fluid level be correct, though, the same symptoms will indicate that the hydraulic system is badly worn. Cross that tractor off your potential buying list!
Some row-crop tractors have dual hydraulic cylinders, which are worthwhile in that they allow the tractor's operator to vary the depth of the front and rear cultivators if necessary. Be on the lookout, also, for a machine with a hydraulic hose coupling, since this feature will allow you to use some of the more recently manufactured hydraulic implements.
Making the Purchase
Once you've decided upon the features you need — and thus narrowed your list of acceptable tractors — you'll be ready to enter the market. But before buying, take the time to get the feel of prices in your area by reading a few weeks' worth of classified ads and visiting the used equipment lots of nearby dealers. Remember, while doing so, that the price of a used tractor purchased from an individual will be lower than that of a new or used machine bought from a dealer ... but that even older models acquired from reputable dealerships will generally have undergone at least some renovation during their stay in the shop.
If you're buying a used machine, approach the purchase as you would that of a previously owned car or truck. Check the tires (replacements for the rear wheels could set you back $200 apiece, or more), and be sure the engine has good compression. Remember, as well, to start the machine up a few times, drive it around (listening carefully for unusual noises), and generally put it through its paces to see how it will handle the lobs you'll later ask it to do.
When buying a used tractor, it's also usually a good idea to purchase as many of the accessories and implements offered with it as you think you might need... even those that could come in handy a bit into the future. It'll often be difficult to find such equipment later, especially if some of it was made expressly for your older tractor. However, remember to let the information picked up while comparing notes with other area farmers help you choose, since the man or woman who's selling you the tractor could well have been talked into buying unnecessary gadgets when he or she first purchased the machine.
You're on Your Own
With a good bit of common sense, a little caution, and the information I've tried to provide in this article, you ought to be able to buy a small farm tractor that suits your pocketbook and your farming needs. With luck, you'll be so pleased with your first purchase that you'll become a strong defender of the brand, whatever it may be. Who knows, you might even become one of those fortunate individuals who — despite the moans and groans with which he or she describes the farmstead workload when talking to friends and relatives — is always on the lookout for an excuse to take a tractor ride!
Thursday, 17 October 2013
Elissa Jobson in Dessie Zuria
|Zenebech Yeman, 30, has benefitted from Concern's programme in her village of Dessie Zruia. Photograph: Jiro Ose/Concern Worldwide|
To mark World Food Day, Elissa Jobson visits Ethiopia's Dessie Zuria district, where planting potatoes has transformed lives
Dessie Zuria is one of the most critically food insecure woredas (districts) in Ethiopia. About 90% of the population is dependent on rain-fed agriculture in the area, where drought is a perennial problem. The high altitude (upwards of 2,400m) restricts the crops that can be grown, and farmers have been reduced to growing a single staple – barley.
The majority of the area's craggy, mountainous terrain is not suitable for agriculture, and soil degradation has reduced the productivity of much of the remaining land. Unsurprising, the local population is highly susceptible to water shortages, and the rate of chronic malnutrition – a staggeringly high 54% – is 10% above the national average.
However, the humble potato – previously unknown in this region of Ethiopia – is helping to transform the lives of thousands of the poorest farmers.
"I was dependent on barley, which is highly vulnerable to the shortage of rain, and my income was very, very minimal," explained Seid Muhie, 30, a farmer from Dessie Zuria's Gelsha kebele parish. "I was ready to sell my land, settle in a nearby town and become a day labourer. But after growing potatoes, I changed my plans."
Muhie was only able to grow 75kg of barley a year on his 1.5 hectare (4.05 acre) plot of land, earning just 450 birr ($24). He found it difficult to support his family. But four years ago, with the help of the NGO Concern Worldwide, he started planting potatoes.
"The harvest was very good. I produced 40 50kg sacks of potatoes from the same plot of land, and I sold them for 170 birr each sack. I was surprised by the income that I could get from the potatoes," Seid said.
In 2007, Concern started a potato pilot project with just 16 households. The yields from that first season were high, and soon the charity was inundated with requests for seed potatoes. So far 10,000 farmers in Dessie Zuria have benefitted from the project, and the woreda administration has rolled the programme out to a further 7,000 smallholders.
"The potato is now becoming a main crop in Dessie Zuria. And nutrition has improved," said Concern project manager Merid Fantaye.
Seid can attest to this. His family now eats potatoes at least four times a week – daily, if there is a food shortage. "The potato is a solution for hunger," he said. "If there is no injera [a flat unleavened bread that is the staple in much of Ethiopia] we don't worry."
Though global hunger has declined by one-third since 1990, about 842 million people are still chronically undernourished. According to the 2013 global hunger index (GHI), published this week, levels of hunger in 19 countries – the majority of them in sub-Saharan Africa – are alarming or extremely alarming, and the overall level of hunger in the world remains serious.
The authors of the GHI, Concern, the German NGO Welthungerhilfe, and the International Food Policy Research Institute, blamed the continued vulnerability to food shortages on unpredictable shocks – from storms and droughts to high food prices and political instability – to which the world's poorest people are continually exposed.
They have called for a wider focus on building resilience to ensure that communities and households are able to deal with the short-term stresses that push them from subsistence into crisis.
Crop diversification – which includes the introduction of apples and pears as well as potatoes – offers a way to build resilience, and is one small part of the integrated development programme that Concern has been implementing in Dessie Zuria and nearby Delanta. Working with the poorest people in these highly impoverished communities, the project focuses on watershed management, small-scale irrigation, the provision of clean water supplies, health and sanitation education, child-feeding techniques, and the economic empowerment of women through microfinancing and self-help groups.
"If you knock on the door of one of the poorest households you can find … food insecurity, water, sanitation and hygiene problems, health problems, inequality and other things. To address these issues, a multi-sectoral approach is very important," said Endalamaw Belay, north area co-ordinator for Concern.
Belay is convinced that this integrated strategy has improved the resilience of farmers in Dessie Zuria. "Previously our beneficiaries had nothing, so they would migrate to another area," he said. "But currently they have a better capacity to resist if there is a drought in the future."
Certainly the residents of Atinit Mesberia kebele are now better able to cope with the failure of rains or other shocks. The construction of terracing on the high peak above the neighbourhood and the building of a small irrigation canal have reaped dividends. The risk of flash flooding has reduced, soil degradation has been halted, and productivity has increased for the watershed's 200 households.
"My wife is also a member of the savings and credit co-operative set up by Concern. She got three ewes and one ram as a credit," said Seid Asan Abegas, 38, who owns a 0.75 hectare plot of land in Atinit Mesberia. He now has 30 sheep, and has constructed two huts from the sale of his livestock – one for his animals, the other for storing hay and seeds – as well as a corrugated iron-roofed house. "Before, I was a dependent on my family," he said. "I had no assets. I am now independent."
Wednesday, 16 October 2013
If you're someone who has trouble remembering when you used fertiliser on your plants or when you watered them, it's time you got yourself a garden journal. This will help you keep track of your greenery.
- A large diary
- A ring-binder
- Coloured tabs or dividers
Gardening is a stress-release activity. So, make sure the pages are light, colorful and fun. Each section can have a vibrant heading, information spaceholders and borders. You can add photos of your own plants to decorate the pages.
Info to include
The journal has to keep a track of all your plants — when you bought and planted them and how to take care of them. Write each plant's common name as well as its botanical name, its light and water requirements and a record of seedlings and cuttings.
Tuesday, 15 October 2013
Having a garden or allotment should be compulsory, Monty Don has argued, as he advocated a sharing scheme in which the elderly, disabled or those who are too busy let others tend their land.
Don, the television gardener, said having a “stake” in the land was essential to ensure a new generation was interested in plants and flowers.
Speaking at the Cheltenham Literature Festival, he argued that everyone should have access to land they can tend, saying all houses must come with a garden, and all flats an allotment.
Failing that, he said, he would like to see a “sharing scheme”, where people who can’t manage their garden, or are “simply happy to share it” could work with those without.
Don was speaking to publicise his latest book, The Road to Le Tholonet: A French Garden Journey. When asked how best to inspire the next generation, he told an audience: “It is a problem. There aren’t enough young people coming through, there aren’t enough young people working as gardeners. And you need to get people interested.
“It’s very easy to get people interested in primary school but by the time someone’s 13 or 14, they don’t want to be thought of as a kid.
“We have a huge drop-out rate at about the age of 10, and then they come back to it about the age of 30. There is a real gap. And yet, whenever I give a talk or go anywhere, the most knowledgable, the most passionate, the most interesting — as well as interested — people are usually somewhere between 22 and 32.
“So why aren’t we tapping into that reservoir? I think it’s partly to do with home-ownership and access to a garden; access to the land.
“If you don’t give people a stake in this land, how are they going to develop?
“I would like to see a garden or an allotment compulsory, so if it’s a flat, it comes with an allotment, and if it’s a house, it has to have a garden.
“I’d also like a sharing scheme, where people who can’t manage their garden, can’t manage all their garden or are simply happy to share it in some way could do so with people who register.
“It does happen where people dig up a garden, grow veg, they have all the vegetables they want and so do the household who owns the garden. Also the grass is cut.
“It’s by doing it that we get interested in gardening. Nobody is going to get interested in gardening by reading books and learning Latin names.”
Foreign aid agencies of two developed countries are assisting Pakistan’s two major provinces to develop their livestock sector on sound lines.
These are Japan International Cooperation Agency (JICA) and the United States Agency for International Development (USAID). JICA has signed an agreement with Sindh government to help revive its livestock potential under a five-year project. The project marks the beginning of implementation of a livestock development master plan jointly worked out by the provincial government and Japanese experts. The plan will cover the period until 2020, based on the scrutiny carried out from 2011 to 2012.
The USAID has helped the Punjab government by preparing a draft of a new law called Punjab Animal Welfare Act, 2013, on behalf of the livestock and dairy development department. It recently organised ‘a dialogue’ among the stakeholders on the pros and cons of the new law in Lahore. The existing law, Animal Protection Act, promulgated by the British in 1822, has become outdated.
Statistics show that Sindh has 6.92 million cattle, 7.34 million buffaloes, 3.96 million sheep, 1.26 million goats and 278,000 camels while the accumulated livestock holdings of the province stands at 21 per cent of the country. According to Japanese experts, the huge size of animal population is in itself a significant sign of the great potential for the livestock development in terms of high production capability. On country-wide basis, the population of cattle was the largest at 38.3 million during 2012-13 — of buffaloes it was 33.7 million, of sheep 28.8 million and of goats 64.9 million.
Meanwhile, a land measuring 2,500 acres has already been earmarked in district Thatta, about 230kms from Karachi, for setting up Bhambhore dairy and meat processing zone by Sindh’s livestock department. Sindh Board of Investment in collaboration with the department would undertake the investment part of the project. The government has started giving some attention to this sector but no big investment, much less from abroad, has been seen in dairy, beef, mutton sub-sectors of livestock.
Most of the livestock production system in Pakistan is age-old and subsistence oriented. Sire (bull) is being bred with low genetic potential. The breed with best potential such as Sahiwal cow and Nili-Ravi buffalo are rarely found on the farms of small and middle-class farmers who contribute a bigger share of cattle-heads. These have, in fact, become endangered species. There is need to save and exploit the genetic potential of the high yielding breeds.
The Punjab government has allocated a sum of Rs7.2 billion for agriculture and livestock sectors in its ADP for 2013-14. Of this, Rs1.7 billion has been allocated for livestock sector. The break-up shows that Rs739 million has been set aside for new schemes in livestock sector and Rs261 million allocated for ongoing schemes.
The budget documents say that livestock is a newly emerging economic sector with high potential in terms of profitability. Farmers earn about 30 to 40 per cent of their income from livestock. Some government initiatives planned in livestock sector are aimed at enhancing production and marketing of livestock products in Layyah, Mianwali, Khushab and Bhakkar, restructuring and re-organisation of breeding services and strengthening of Buffalo Research Institute at Pattoki.
A by-product of the livestock sector is bio-gas and China has set up 11 million biogas plants by using cattle’s manure. But Pakistan has hardly 3,000 plants. Based on the size of cattle and other animal population, Pakistan can have as many as a million biogas plants. Punjab’s chief minister has, however, taken the initiative on this count. He has launched a project aimed at developing economical biogas plants. Apart from clean fuel, these plants also produce organic fertiliser as a by-product. Another by-product is leather and leather products. Its exports earned $1.1billion during 2010-11 fiscal year which amounted to 4.4 per cent of the total exports.
Historically, livestock has been mostly pursued by small farmers to meet their needs of milk, meat, eggs, food security and cash income on daily basis. Some 30-35 million people in rural areas depend directly or indirectly on livestock for their livelihood. Pakistan happens to be the fifth-largest milk producer in the world but has yet to develop this sub-sector as a large-scale industry and to make it one of the leading foreign exchange earners. The milk production, however, increased by 3.2 per cent and meat 4.5 per cent during 2012-13 as compared to corresponding period last year.
Livestock contributed approximately 55.4 per cent to the agricultural value and 11.9 per cent to the GDP during 2012-13, against almost similar performance a year ago. Gross value addition of the livestock sector at constant cost factor has increased from Rs735 billion (2011-12) to Rs756 billion (2012-13), showing an increase of 2.9 per cent as compared to previous year.
In the wake of the passage of 18th constitutional amendment, the federal ministry of livestock and dairy development was abolished on April 5, 2010 and the subjects of animal health and production were devolved to the provinces. The technical staff of the ministry was initially attached with the commerce ministry and later with livestock wing of the newly created ministry of national food security & research in February 2012. The ministry is redefining its role under its new mandate to serve as catalyst in the development of livestock in the country.
The future plan of the ministry for livestock sector is to achieve five per cent growth in meat and eight per cent in milk production, which are currently around three per cent, by discouraging subsistence livestock farming and encouraging market-oriented and commercial farming covering the entire value chain from farm to plate.
Besides, the ministry plans to promote diversification of livestock products, help the sector play a leading role in the global halal food market and control trans-boundary animal diseases of trade and economic importance. Ashfak Bokhari
Monday, 14 October 2013
Planting roses isn't actually complicated, as long as you have some good advice and tips to start with...
1. Check with your local gardening center or florist for the best type of roses to grow in you climate. If you are a novice, you should look fo? disease resistant types of roses because they require a lot less maintenance.
2. When planting roses, you want to pick a spot that is well lit in the morning. You also want an area that is sunlit for at least 6 hours a day. Roses need a great deal of light if they are to grow properly. If you live in a really hot climate though, you'll probably get the best results by not planting your roses in direct sunlight.
3. Pick an area that has plenty of well drained soil. Great soil has a PH level where the amount of acid in the soil is at about 5.5-7.0. You can get a testing kit for your soil at any garden center.
4. Organic matter like manure or lime helps to nourish the roots of your roses. You should soak the roots in water or puddle clay for many minutes, and cut off any root's ends that are broken.
5. The first 3-4 weeks after planting your roses, you should water them often. Usually this is when the top 2 inches of soil is dry. Roses need a lot of hydration and food to remain healthy.
6. Four weeks after planting, you should start soaking the bed every 2 weeks or so. You should do this in the morning for the best results.
7. Begin fertilization approximately 3 months after planting. Use 3-6 inches of mulch to control the moisture, temperature, and to stops weeds from coming up. Mulch also helps to lock in the vital nutrients your roses need in order to remain healthy.
8. Planting in the Spring is the best.
9. You want to plant your roses in an area that is well circulated with air. Your roses will not grow in an enclosed or tight area.
10. Dig a hole that is two times bigger than the amount of space that your roses take up. It makes it easier to plant them and creates a spaced area for them to grow with freedom. Poor circulation for your roses can cause fungal diseases. Using a larger hole also makes it easier for you to pull them up later and pot them if you'd like
Sunday, 13 October 2013
How many badgers are infected, will enough badgers be culled and is it all worth it? Here is a guide to the recent badger cull
Most badgers aren't infected, is that correct?
The largest study of bovine tuberculosis (TB) in badgers was the randomised badger culling trial, RBCT, which reported in 2007. Nearly 8,900 badgers were culled across large (100 km sq) areas where there was high risk of cattle TB. Their carcasses were subjected to detailed examination and testing, although the standard postmortems missed half of the infections compared with extended postmortems. Overall, 16.6% of the badgers culled between 1998 and 2005 were found to be positive, based on the standard postmortem, indicating that about 33% were actually infected. But this percentage varied geographically and by year in the trial.
Do cattle really catch TB from badgers?
Most badgers are not infected, but those that are can transmit infection to cattle. Using a mathematical model and data from the start of the trial, I estimated that confirmed cattle TB rates would be halved if there were no transmission from badgers (meaning neither direct badger-to-cattle transmission nor onward cattle-to-cattle transmission of those primary infections). But this estimate is quite uncertain. Even without using the model, it is clear that in an 18-month period after widespread culling stopped in the trial, cattle TB in the culling area was reduced by roughly half. This estimate was more precise, being almost certainly between 38% and 66%. Thus, it is very likely that at least 38% of the confirmed cattle TB in trial areas stemmed from badger-to-cattle transmission, with half being the best estimate.
What is "perturbation" and why does it matter for cattle?
|The results of the £50m randomized badge culling trial that ended in 2006 showed that, five years after a series of four annual culls, there was a reduction in confirmed TB infections in cattle in the cull zones|
There are fewer badgers per square kilometre in recently culled areas (unsurprisingly), but the badgers found there ranged more widely. This behavioural effect has been called social "perturbation". Areas with fewer badgers ranging more widely had reduced cattle risks when the reduction in badger density was large (70%). However, in areas with much smaller reductions in badger densities (in particular, land up to 2km outside extensive culling areas and areas subjected to small, reactive culls) there were increased cattle infections, presumably due to the increase in contact with perturbed, infected badgers. Within the trial, badgers culled in areas previously subjected to recent culling were more likely to be infected, presumably due to the perturbation.
Can we really expect a 16% reduction in cattle TB over several years for a single big cull?
The 16% figure was an estimate for the local impact of repeated culls over 150 km sq, taking into account the assumption that the background risk of cattle TB was higher in the culling area than on the land up to 2km outside it. It is not a 16% reduction nationally. Indeed, the impact of a single such cull would not be visible in national statistics.
16% was an average over several years of the cattle risk reduction, observed inside the culling area during four years of annual culling and in the years after culling stopped, set against the cattle risk increase observed up to 2km outside the culling area during the years of annual culling.
How was the number of badgers to be culled arrived at?
For a particular cull zone, the size of the badger population was estimated (call this estimate N). The minimum cull number was then set sufficiently high to be confident that at least 70% of badgers would be culled. Due to statistical uncertainty in the estimate N, that minimum figure was more than 70% times N.
Will the current pilot culls be able to remove enough badgers?
We will have to wait for the report of the independent panel after the pilot culls have finished. The uncertainty over whether enough badgers can be removed (so that the reduction in badger density more than offsets the impact of badger perturbation) arises due to the use of a badger culling technique not used in the RBCT: shooting of free-running badgers. If substantially fewer than 70% of badgers were removed, there would be a risk that the population reduction was insufficient to reduce TB risks to cattle. In a worst-case scenario, it could conceivably be low enough to increase TB risks to cattle, due it seems to social perturbation of the remaining badger population. The tipping point for a reduction in badger density at which a cattle risk reduction becomes a cattle risk increase is not known. This has been a key concern among scientists arguing against the current culling approach.
The government is culling badgers in England. Why don't they cull cows instead?
The government does cull so-called "reactor" cattle every year, after they "reacted" to a diagnostic skin test for TB. In 2012 more than 28,000 cattle were slaughtered in England to control TB. Cattle slaughtered for consumption are also inspected to detect any evidence of infection. Bovine TB control currently costs the government (in other words taxpayers) about £90m a year.
Is badger culling worth doing?
This is the big question. The answer cannot just be purely scientific. There are ethical, animal welfare and economic aspects, in addition to health and safety issues, that must be considered. However, science can provide quantitative predictions for many of the important "what if we?" questions.
• Christl Donnelly is professor of statistical epidemiology at Imperial College London and was a key member of the randomised badger culling trial (RBCT).