Better Brassica Management
Brassicas such as kale, swedes, turnips and rape, can provide high yielding, high quality standing green feed suitable for wintering stock, and as a supplement to pasture in early lactation. Brassicas comprise the largest area of cultivated crops in NZ with well over 250,000 ha grown annually.
While farmers are good at managing pastures they often lack expertise in growing and managing brassicas well. As a result, yields vary widely, and intensive grazing under wet winter conditions can lead to poor utilisation, long-term soil damage, and N and P losses to the environment.
Crop & Food Research is hoping to set up demonstration sites in a number of areas to show what is possible. A great deal is known about brassicas, and they hope to be able to pass this information on.
This project is to encourage farmers to look at the mature crops they are feeding out at present and assess how well they have performed in terms of establishment and management of the growing crop. It looks at the variation in crop yield due to differences in cultivation and management, and especially at the problems of pugging, soil compaction and environmental contamination that need to be avoided on dairy farms.
Brassicas are grown on the central plateau of the Nth Island for summer fodder and extensively in the Sth Island as winter fodder. They are the supplement of choice for many Sth Island dairy farmers.
However, establishment and management of these crops is often poor and huge variations in yield can occur within the same district. Also, while the technology to produce high yielding crops is well known, less is known about utilising them efficiently and producing them sustainably.
Intensive grazing of forage crops during wet winter conditions often leads to poor utilisation and long-term damage to soil quality, with consequent effects on the productivity of the following crops or pasture. Nutrient losses (particularly N and P) from winter crops are also are a real concern.
Well-grown crops can have double the DM output for the same level of inputs. Dr Derek Wilson, crop physiologist with Crop & Food Research, says that if crops are managed effectively, the required dry matter can be grown at half the cost and on half the land area.
In the past three years, we have found yields of 20 to 25 tonnes DM/ha of kale have been produced consistently in Canterbury trials. Similarly, some of the best swede crops in Southland produce over 20 t DM/ha, says Derek.
However, actual yields of winter brassicas are usually well below that. Swede yields in Southland typically range from about 5 to 20 t DM/ha, with a few good crops a little higher, and recent kale fertiliser response trials around NZ have shown yields from 4 to 19 tonnes DM/ha.
There are many causes of low brassica yields. Common ones are:
poor crop establishment
pest problems
lack of water
low soil fertility
inadequate fertiliser
Care is needed with these crops because they can develop high concentrations of undesirable N and S compounds that can be toxic.
They have an unusual nitrogen and sulphur metabolism, and they have compounds in then that can be anti-nutritional and even toxic in higher concentrations, so management of the fertiliser and fertility during the growth of the crops is quite important to make sure that the nitrogen and sulphur ratios don't get out of balance, says Derek.
We are also doing trials at the moment trying to define the soil fertility conditions that create the higher risk of N & S compounds in crops. Because farmers are starting to grow these crops more intensively and putting more fertiliser on them the risk is probably greater.
Limiting grazing at times of risk is also a means of avoiding stock health problems.
Feeding out brassicas under wet conditions is a mission. There is a conflict between the need confine stock to a small area to ensure good utilisation (you can lose 70% of the crop through trampling), and the risk of severe pugging and soil structure damage.
Unfortunately, the combined effects of high yield, high N from dung and urine, and intensive grazing under wet conditions also leads to N losses to the environment.
There are no easy solutions, according to Derek, but farmers should take care to:
Select paddocks that are on suitable soil types
Have a good rotation
Prepare the land well so it can tolerate the treatment that the soil is going to get during grazing
At grazing time use electric fencing to give the animals small areas so that they are not wasting too much of the crop
Have the animals on the grazing area for a short time then move them off
Try to avoid the stock trampling over the grazed area when other breaks are opened up.
In the longer-term, says Derek, it may be better to have feed pads for the stock, cutting and carrying the crop to the pad.
This would reduce the soil and environmental impacts. We might also be looking at other ways of conserving these crops, such as making silage or baleage out of them, he says.
Crop & Food, along with Lincoln University and AgResearch, have an application into the MAF Sustainable Farming Fund to fund a major technology transfer project on brassica crops, aiming to show farmers how to improve the performance of both summer and winter brassicas through a mixture of seminars, field days and trials and demonstration areas throughout the country.
While farmers are good at managing pastures they often lack expertise in growing and managing brassicas well. As a result, yields vary widely, and intensive grazing under wet winter conditions can lead to poor utilisation, long-term soil damage, and N and P losses to the environment.
Crop & Food Research is hoping to set up demonstration sites in a number of areas to show what is possible. A great deal is known about brassicas, and they hope to be able to pass this information on.
This project is to encourage farmers to look at the mature crops they are feeding out at present and assess how well they have performed in terms of establishment and management of the growing crop. It looks at the variation in crop yield due to differences in cultivation and management, and especially at the problems of pugging, soil compaction and environmental contamination that need to be avoided on dairy farms.
Brassicas are grown on the central plateau of the Nth Island for summer fodder and extensively in the Sth Island as winter fodder. They are the supplement of choice for many Sth Island dairy farmers.
However, establishment and management of these crops is often poor and huge variations in yield can occur within the same district. Also, while the technology to produce high yielding crops is well known, less is known about utilising them efficiently and producing them sustainably.
Intensive grazing of forage crops during wet winter conditions often leads to poor utilisation and long-term damage to soil quality, with consequent effects on the productivity of the following crops or pasture. Nutrient losses (particularly N and P) from winter crops are also are a real concern.
Well-grown crops can have double the DM output for the same level of inputs. Dr Derek Wilson, crop physiologist with Crop & Food Research, says that if crops are managed effectively, the required dry matter can be grown at half the cost and on half the land area.
In the past three years, we have found yields of 20 to 25 tonnes DM/ha of kale have been produced consistently in Canterbury trials. Similarly, some of the best swede crops in Southland produce over 20 t DM/ha, says Derek.
However, actual yields of winter brassicas are usually well below that. Swede yields in Southland typically range from about 5 to 20 t DM/ha, with a few good crops a little higher, and recent kale fertiliser response trials around NZ have shown yields from 4 to 19 tonnes DM/ha.
There are many causes of low brassica yields. Common ones are:
poor crop establishment
pest problems
lack of water
low soil fertility
inadequate fertiliser
Care is needed with these crops because they can develop high concentrations of undesirable N and S compounds that can be toxic.
They have an unusual nitrogen and sulphur metabolism, and they have compounds in then that can be anti-nutritional and even toxic in higher concentrations, so management of the fertiliser and fertility during the growth of the crops is quite important to make sure that the nitrogen and sulphur ratios don't get out of balance, says Derek.
We are also doing trials at the moment trying to define the soil fertility conditions that create the higher risk of N & S compounds in crops. Because farmers are starting to grow these crops more intensively and putting more fertiliser on them the risk is probably greater.
Limiting grazing at times of risk is also a means of avoiding stock health problems.
Feeding out brassicas under wet conditions is a mission. There is a conflict between the need confine stock to a small area to ensure good utilisation (you can lose 70% of the crop through trampling), and the risk of severe pugging and soil structure damage.
Unfortunately, the combined effects of high yield, high N from dung and urine, and intensive grazing under wet conditions also leads to N losses to the environment.
There are no easy solutions, according to Derek, but farmers should take care to:
Select paddocks that are on suitable soil types
Have a good rotation
Prepare the land well so it can tolerate the treatment that the soil is going to get during grazing
At grazing time use electric fencing to give the animals small areas so that they are not wasting too much of the crop
Have the animals on the grazing area for a short time then move them off
Try to avoid the stock trampling over the grazed area when other breaks are opened up.
In the longer-term, says Derek, it may be better to have feed pads for the stock, cutting and carrying the crop to the pad.
This would reduce the soil and environmental impacts. We might also be looking at other ways of conserving these crops, such as making silage or baleage out of them, he says.
Crop & Food, along with Lincoln University and AgResearch, have an application into the MAF Sustainable Farming Fund to fund a major technology transfer project on brassica crops, aiming to show farmers how to improve the performance of both summer and winter brassicas through a mixture of seminars, field days and trials and demonstration areas throughout the country.