There has been a notable decline in soil fertility nationally and the impact is even more serious on heavy soils farms. On heavy soils there is the potential to increase annual grass production by 30% where pH, P and K status is optimum.
Seven dairy farms farming on heavy soil type are participating in a monitoring and development programme and contributing key data on farm performance. The farms are deemed heavy, eg predominately clay mineral soils located in high rainfall areas of the southwest of Ireland
Data over the period 2011-2014 shows that on the heavy farms, grass growth varied from 6.8 tonnes DM/ha in 2012 to 11t DM/ha in both 2014 and 2015.
Changes in soil fertility 2010-2015
It has been firmly established in research that soil pH must be corrected as a first step to overall improvement in soil fertility status.
Farmer participants embarked on a programme of soil fertility improvement in 2010. The low pH was due in part to a trend of low usage of lime nationally with higher nitrogen usage masking the impact of low pH on grass growth.
2013 fertiliser plans showed that on a farm size of 68ha, stocked at 1.8 LU/ha that there was a total lime requirement of 278t. The farms have applied on average 90t ground limestone per annum and the impact on farm pH is shown in Table 1. 2015 average fertiliser costs were 3.3c/l on the heavy soils farms with lime accounting for 0.42c/litre of that cost. A comprehensive soil testing programme took place across all the heavy soils farms in December 2015 and the summary outcome is presented in Table 1.
Average pH has increased from 5.7 to 6.1. All but one of the seven farms showed a pH increase. The farms are continuing to focus on applying further lime in 2016 to bring all paddocks to target pH of 6.3 .No noticeable change in soil trafficability has been observed by the farmers largely due to quantities applied being limited to 2t per acre in any one application
P and K Status
Both P and K status has, disappointingly, declined in 2015.The higher P offtake due to increased cow numbers (+15 cows extra per farm since 2011) and 12% high milk solids production compared to 2014 combined with many paddocks still with pH less than six, which is leading to a continuing lock-up (fixation) of applied phosphorus.
K status is closely linked to P status due to the use of compound fertilisers also the higher leaching impact on K of high rainfall. P and K offtake in product leaving the farm becomes even more significant in a quota free environment. All farms need to be aware of this increasing demand for nutrients as milk production increases. A continuing poor response to additional P applications on low pH paddocks on the heavy clay soils is very evident due to fixation.
Lime and loss through drainage/rainfall losses
Because these farms are located in high rainfall areas lime loss is estimated at up to 625kg/ha/year or a loss through drainage alone of 1.2t/acre in a five-year time frame. In addition, lime is required to counteract acidity from chemical N use and loss in milk/meat means a maintenance requirement of 2t/acre every five years is required on these farms.
In effect, any lime applied in 2011-2014 was only keeping pace with the maintenance requirement and was not having an impact on lifting farm soil pH.
Timing of lime application
Lime can be applied at any time of year when ground conditions are suitable. Outside of the normal application peaks at reseeding and late autumn, monthly lime usage statistics suggest that very little lime is applied in the June period. This coincides with a period on grassland farms that grass is being harvested for silage or taken as surplus quality bales (stubble available) and when ground conditions are good for spreading.
For example, a 33ha milking block stocked at 3.5 cows/ha in May/June can potentially have 33% of the area suitable for lime application in June as grass stubble after silage plus paddocks grazed in the previous week or taken as surplus. This would allow two lorries of lime (40t) be applied without any negative impact on animal intake, etc. The key is to have the lime in the yard in mid-May ready to go when the opportunity arises.
Conclusions
Increased productivity on heavy soils requires a clear management focus on increasing soil fertility in a planned manner. In particular, a renewed campaign of lime application is required on all heavy soils programme farms. Stocking rates must be matched to the grass growth and utilisation capacity of the farm .Based on grass grown of 12.5t DM/ha with all winter feed requirement conserved within the farm (including reserve) a potential stocking rate of 2 LU/ha is achievable.
The nature of nutrient behaviour on heavy soils makes it imperative that soil pH is corrected before embarking on high applications of organic/chemical fertilisers.A plan is required that sets out a target tonnage of lime to be applied on farm in 2016.Ideally spread lime when ground conditions are good over the summer period. June is often a suitable time when little lime is applied nationally.A little and often approach works best where high rainfall can lead to excessive losses through drainage and high lime applications can impact on soil trafficability.To read the full Fertilizer Focus Supplement click here.
There has been a notable decline in soil fertility nationally and the impact is even more serious on heavy soils farms. On heavy soils there is the potential to increase annual grass production by 30% where pH, P and K status is optimum.
Seven dairy farms farming on heavy soil type are participating in a monitoring and development programme and contributing key data on farm performance. The farms are deemed heavy, eg predominately clay mineral soils located in high rainfall areas of the southwest of Ireland
Data over the period 2011-2014 shows that on the heavy farms, grass growth varied from 6.8 tonnes DM/ha in 2012 to 11t DM/ha in both 2014 and 2015.
Changes in soil fertility 2010-2015
It has been firmly established in research that soil pH must be corrected as a first step to overall improvement in soil fertility status.
Farmer participants embarked on a programme of soil fertility improvement in 2010. The low pH was due in part to a trend of low usage of lime nationally with higher nitrogen usage masking the impact of low pH on grass growth.
2013 fertiliser plans showed that on a farm size of 68ha, stocked at 1.8 LU/ha that there was a total lime requirement of 278t. The farms have applied on average 90t ground limestone per annum and the impact on farm pH is shown in Table 1. 2015 average fertiliser costs were 3.3c/l on the heavy soils farms with lime accounting for 0.42c/litre of that cost. A comprehensive soil testing programme took place across all the heavy soils farms in December 2015 and the summary outcome is presented in Table 1.
Average pH has increased from 5.7 to 6.1. All but one of the seven farms showed a pH increase. The farms are continuing to focus on applying further lime in 2016 to bring all paddocks to target pH of 6.3 .No noticeable change in soil trafficability has been observed by the farmers largely due to quantities applied being limited to 2t per acre in any one application
P and K Status
Both P and K status has, disappointingly, declined in 2015.The higher P offtake due to increased cow numbers (+15 cows extra per farm since 2011) and 12% high milk solids production compared to 2014 combined with many paddocks still with pH less than six, which is leading to a continuing lock-up (fixation) of applied phosphorus.
K status is closely linked to P status due to the use of compound fertilisers also the higher leaching impact on K of high rainfall. P and K offtake in product leaving the farm becomes even more significant in a quota free environment. All farms need to be aware of this increasing demand for nutrients as milk production increases. A continuing poor response to additional P applications on low pH paddocks on the heavy clay soils is very evident due to fixation.
Lime and loss through drainage/rainfall losses
Because these farms are located in high rainfall areas lime loss is estimated at up to 625kg/ha/year or a loss through drainage alone of 1.2t/acre in a five-year time frame. In addition, lime is required to counteract acidity from chemical N use and loss in milk/meat means a maintenance requirement of 2t/acre every five years is required on these farms.
In effect, any lime applied in 2011-2014 was only keeping pace with the maintenance requirement and was not having an impact on lifting farm soil pH.
Timing of lime application
Lime can be applied at any time of year when ground conditions are suitable. Outside of the normal application peaks at reseeding and late autumn, monthly lime usage statistics suggest that very little lime is applied in the June period. This coincides with a period on grassland farms that grass is being harvested for silage or taken as surplus quality bales (stubble available) and when ground conditions are good for spreading.
For example, a 33ha milking block stocked at 3.5 cows/ha in May/June can potentially have 33% of the area suitable for lime application in June as grass stubble after silage plus paddocks grazed in the previous week or taken as surplus. This would allow two lorries of lime (40t) be applied without any negative impact on animal intake, etc. The key is to have the lime in the yard in mid-May ready to go when the opportunity arises.
Conclusions
Increased productivity on heavy soils requires a clear management focus on increasing soil fertility in a planned manner. In particular, a renewed campaign of lime application is required on all heavy soils programme farms. Stocking rates must be matched to the grass growth and utilisation capacity of the farm .Based on grass grown of 12.5t DM/ha with all winter feed requirement conserved within the farm (including reserve) a potential stocking rate of 2 LU/ha is achievable.
The nature of nutrient behaviour on heavy soils makes it imperative that soil pH is corrected before embarking on high applications of organic/chemical fertilisers.A plan is required that sets out a target tonnage of lime to be applied on farm in 2016.Ideally spread lime when ground conditions are good over the summer period. June is often a suitable time when little lime is applied nationally.A little and often approach works best where high rainfall can lead to excessive losses through drainage and high lime applications can impact on soil trafficability.To read the full Fertilizer Focus Supplement click here.
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