Grassland Managing nutrients for profitable grass production. The Authority in Potassium and Magnesium

Transcription

1 Grassland Grassland Managing nutrients for profitable grass production The Authority in Potassium and Magnesium

2

3 Grass The best value feedstuff 3 Maintaining a low cost supply of animal feed is one of the key requirements for success in livestock farming. Feeding grass reduces the reliance on bought-in feed and therefore lessens some of the effects of commodity price volatility which has been a major difficulty for the livestock sector in recent times. Grass is particularly well suited to the temperate UK climate and has the potential to yield over 2t/ha dry matter. However, good yields of highly digestible quality forage are possible only with knowledge and attention paid to the nutritional requirements of both grass and clover. Cost of energy from different feed sources Grazed grass Grass silage Kale Forage turnips Brewers grains concentrates Nix, 211 Cost p/mj of ME in DM The greater the proportion of energy that can be derived from home-grown forage, the higher the profitability of the farming enterprise. Influence of energy content of forage on milk yield Energy content of grass silage (MJ NEL / kg DM) DM intake (kg/cow/day)* Energy intake (MJ NEL/cow/day) Potential milk yield * Calculated from Gruber et al 25 DM = Dry matter MJ = Megajoule NEL = Net Energy Lactation Perennial ryegrass Lolium Perenne One of the best maritime grasses for intensively grazed meadows and grassland with high trampling pressure.

4 Soil fertility 4 It is essential that soil nutrients are maintained at the levels recommended by DEFRA if the economic optimum in forage production is to be achieved. It is estimated that fewer than 5% of livestock farms regularly take soil samples. Soil analysis will rapidly and accu- rately inform you what you do need and in many cases, what you don t! Recommended soil levels for P, K and Mg are conveniently put into an index system and the target soil index for P, K and Mg is 2 (2- for potash). Index Index 1 Index 2 Index 3 Phosphorus* (P) mg/l Potash (K) mg/l Magnesium (Mg) mg/l (2-) (2+) * Olsen's method Nutrients should be applied to replace those removed from the field and if soil index is below the recommended target, additional nutrient should be applied to build up soil fertility. Conversely if nutrient levels are above target, then reduced quantities can be applied or even omitted to run down soil levels to target. The following tables reproduced from the Fertiliser Manual give current advice from the 21 edition. Nutrient recommendations (kg/ ha) Grazed grass Index Phosphate (P 2 O 5 ) Potash (K 2 O) Magnesium (MgO) * 25* Grass establishment Index Phosphate (P 2 O 5 ) Potash (K 2 O) Magnesium (MgO) (2-) 4 (2+) * 25* * Recommended by K+S Kali GmbH to help to maintain a healthy balance of minerals in grass which can help to prevent metabolic disorders, such as staggers.

5 5 Considerably higher quantities of nutrients are required for fields in silage or hay production due to the high yields achieved and the fact that vast quantities of dry matter (and therefore nutrients) are removed from the field and need to be replaced. Grass silage Index Magnesium (total for year) * 25 * st cut 23 t/ha Phosphate (P 2 O 5 ) Potash (K 2 O) - previous autumn - spring (2-) 6 (2+) 3 2 nd cut 15 t/ha Phosphate (P 2 O 5 ) Potash (K 2 O) (2-) 6 (2+) 4 3 rd cut 9 t/ha Phosphate (P 2 O 5 ) Potash (K 2 O) (2-) 4 (2+) 2 4 th cut 7 t/ha Phosphate (P 2 O 5 ) Potash (K 2 O) (2-) 4 (2+) 2 Note: Yields shown are appropriate to typical wilted silage at 25% DM. Where yields are higher or lower, nutrient rates should be adjusted accordingly.

6 6 The use of fertilisers in grassland has a direct influence on: yield the botanical composition of the sward the palatability of the forage protein and energy values mineral content And hence the productivity and fertility of the livestock. If grassland becomes short of nutrients, quality and yield are sacrificed. In years where fertiliser use is reduced, clear reductions in energy and protein content are seen. Changes in botanical composition with use of mineral fertilisers Omitting certain nutrients has a profound effect on the sward composition. Where potash was omitted, there was a marked reduction in dry matter yield and when only NK fertiliser was applied, the proportion of the weeds species increased sharply at the expense of the valuable grasses and legumes. When only N fertiliser was applied, this resulted in even lower yield than any other plots due to poor N-use efficiency in the absence of supporting nutrients. Yield and botanical sward composition of a grassland meadow (three cuts following different fertiliser applications, ) Nutrients applied (kg/ ha) Yield (t/dm/ha) Proportion of the sward composition (%) N P 2 O 5 K 2 O* Grasses herbs legumes *K 2 O applied as Korn-Kali Diepolder, LfL Freising 25

7 Grassland A crop with a high demand for nutrients 7 Grassland, particularly intensively managed grass and that which is cut for conservation, has a very high demand for all nutrients, in particular nitrogen, sulphur and potash. Animals however generally receive these minerals in excess and demand more sodium and magnesium. Magnesia-Kainit provides a balance of nutrients essential for both grass and stock and for this reason is sometimes called the 'stockman's fertiliser'. The quantity of nutrients removed from the field in conserved grass is frequently underestimated. The following table shows the nutrient removal from conserved grass with different yield levels and cutting regimes. Effect of site, cutting intensity and yield on nutrient removal from silage fields Net yield P 2 O 5 K 2 O MgO SO 3 (t DM/ ha) (kg/ t DM)(kg/ ha) (kg/t DM) (kg/ ha) (kg/t DM) (kg/ ha) (kg/t DM) (kg/ ha) High yielding areas 3 cuts cuts cuts Lower yielding areas 2 3 cuts cuts cuts Source: DVO amended The potash removal by silage making is all too often ignored and the depletion of K status in such soils can be rapid and dramatic unless sufficient potash is replaced. First cut silage in an intensive situation nutrient Conversion offtake analysis in% factor kg/ha protein 16.9 x.16 yield 3.5 t DM/ha 95 N P.35 x 2.29 x = 28 P 2 O 5 K 2.87 x K 2 O Mg.2 x MgO Ca.65 x CaO Meadow foxtail Alopecurus pratensis Early flowering perennial usually present from the wild and preferring moist fertile soils. Produces high quality pasture grazing and hay. Note the potash removal of a typical high yielding 1 st cut of silage (12 kg K 2 O/ha) is higher than all other nutrients including Nitrogen.

8 Organic manures 8 FYM and slurry are valuable sources of nutrients for grassland but the recycling of nutrients is always less than 1% and therefore use of mineral fertilisers is required to make up the balance. This is of particular importance in fields far from livestock housing which typical- ly get less slurry applications and are frequently found to be below the recommended nutrient indices. New relatively simple analysis tools exist for analysing the nutrients in manures and provide a useful baseline for making a nutrient plan or balance for the farm. Nutrient content of a range of organic manures Unit DM % Available Available Total phosphate potash Magnesium Kg P 2 O 5 Kg K 2 O Kg MgO Cow slurry 1m Pig slurry 1m FYM 1 tonne Sewage sludge (Digested cake) 1 tonne Source: RB29, 21 Note that both sewage cake and FYM contain relatively high quantities of phosphate but that a typical annual application of cattle slurry (5 m 3 /ha) supplies only around half of the annual potash offtake from a multi-cut silage field. Organic manures contain low levels of magnesium and also sulphur (typically around kg SO 3 /m 3 ) although this is almost all bound in organic and/or insoluble forms and is largely unavailable for short term plant uptake. For this reason, current advice in DEFRA s Fertiliser Manual (RB29) is that both sulphur and magnesium from organic sources should largely be regarded as contributing only to the maintenance of soil reserves. Large applications of slurry contain reasonable quantities of potash and typically very little sodium and magnesium as these are not readily excreted by the livestock. This inbalanced K-rich slurry has the effect that it depresses sodium and magnesium content of the forage. By using Magnesia-Kainit as a slurry partner, potash can be topped up, magnesium and sodium in the forage are incereased for healthier mineral content and the palatability of grass after slurry spreading is greatly improved.

9 9 The potash balance in UK grassland is usually negative because the nutrient contribution from organic manures is frequently overestimated. Supplementation with mineral fertilisers is usually necessary to replace nutrients that leave the farm in meat, milk and through leaching. Even on highly intensive farms with 2 3 LU*/ ha, the danger exists that the potash requirement will not be met by organic manures alone and the negative balance will eventually deplete soil fertility. A recent PAAG report (21) concluded that currently 45% of all soils from UK livestock farms are below the target index for K. The following table shows the typical shortfall of P and K for different silage-making scenarios. P and K requirements for typical 3-cut silage grass following slurry applications annual 6% DM cattle slurry m 3 /ha 25 (1 LU*) 38 (1.5 LU) 5 (2 LU) P 2 O 5 from slurry K 2 O from slurry Typical annual offtake P 2 O 5 K 2 O nutrient requirement at index 2 - P 2 O 5 K 2 O kg/ ha Korn-Kali kg/ ha Korn-Kali Additional potash requirement 387 kg/ ha Korn-Kali * 1 LU (livestock unit) represents one 65kg cow. The values in the table are valid for fields at the target index 2- for K. Many fields are below target index however and so additional potash will be required to build the fertility to the required level for satisfactory yield performance. Target concentrations of potash, magnesium and sodium in forage. The mineral composition of grass changes as the season progresses with high K, low Mg and Na early in the Spring whilst in Autumn, K levels drop and Na and Mg typically increase. However some critical levels and ratios exist and should be used as a guide for healthy livestock (see page 15). K content in grass (% DM) Seasonal changes in the K content of grass March April May June July August Italian ryegrass Permanent pasture The potash requirement of the livestock and the forage differ considerably. As a mineral nutrient for animal nutrition, potassium is seldom in short supply because the K content of forage is more than adequate for animal health. However for efficient grass growth, a minimum of 2.5% K content (in DM) is necessary to prevent yield and quality losses.

10 Forage quality with Magnesium and Sulphur 1 Magnesium deficiency is costly Magnesium deficiency in forage is common and is usually mirrored by low blood magnesium in the livestock. This danger appears especially in the spring in grass which is also low in raw fibre. One resulting consequence is the condition hypomagnesaemia, more commonly known as grass tetany or staggers after the staggering gait seen in affected animals. Not only is the magnesium supply in the forage low, the absorption by the animal is often poor at this time due to low sodium levels in the soil and also the forage. A minimum target level should be.2% Mg in the forage dry matter. See page 15 for more information. Sulphur for protein building Sulphur is absolutely essential for forage crops to partner nitrogen in building valuable protein. If sulphur is lacking then the use efficiency of N is drastically reduced with economic and environmental consequences. Sulphur is present in organic manures but is mostly bound up in organic matter and needs breaking down or mineralising before it can be used by plants. This process can be slow over many years and only starts when soil temperatures reach around 1 C, long after grass growth has begun and N is taken up. For this reason, sulphur from manures should not be relied upon for the current years growth and should only be considered as contributing to background soil levels. For the production of high protein content in the forage, a sufficient provision of plant-available sulphur (sulphate) is absolutely necessary. The low sulphur content in slurry is only around 5 1% plant available and therefore an application of a suitable source of fast-acting sulphate (SO 4 ) sulphur from mineral fertiliser is indispensable. Forage analysis indicates a clear sulphur deficiency when an N:S ratio of greater than 15:1 is found. A figure of less than 12:1 is optimal and between 12:1 and 15:1 there is a danger that protein formation will be impaired. A survey of recent forage analysis results indicated than around threequarters of all Silage analyses were deficient in sulphur. In order to calculate this N:S ratio, the forage sample must be analysed for sulphur. The N value is determined by multiplying the protein content by.16. DM (t/ha) Grass yield response to different forms of applied sulphur Spitalhof The temperature dependent sulphur mineralisation is clearly apparent where only slurry was applied. The trials also highlighted the important difference in the effectiveness of two different sources of mineral S fertiliser. When Magnesium sulphate was applied in addition to the slurry, there was a clear increase in DM yield of over 8%. 1. Slurry Slurry + elemental S Slurry + sulphate S Sulphur applied in the sulphate form is worth almost 1 tonne of DM/ha more compared to sulphur applied in elemental form. Source: M Diepolder 24

11 11 Sulphur content of different silage cuts following application of ESTA Kieserit fertiliser S content of forage (% DM) st cut 2 nd cut 3 rd cut kg/ha S 5 kg/ha SO 3 1 kg/ha SO 3 Source: DLR Westerwolds Montabaur, Brenner, 26 Two experiments at LWK Oldenburg over 5 years with S use of fertilizers also resulted in marked improvements of the Silage quality: Increase in crude protein of between.9% and 3.8% Reduction in raw fibre content of between -.2% and - 6.5% Higher energy content of between.3 and 1.2 MJ/kg NEL Moreover, the energy content of the silage was better preserved during the clamping period. Because K+S Kali fertilisers contain magnesium from Kieserite (natural magnesium sulphate), the most plant available form of sulphur is also applied to the grass. The use of Magnesia-Kainit, Korn-Kali, Patentkali or ESTA Kieserit rapidly satisfies both the magnesium and the sulphur demand of the most demanding of forage crops. Timothy Phleum pratense Tall perennial prized for high quality haymaking. Prefers nutrient-rich soils.

12 12 Muriate of potash (MOP) ESTA Kieserit gran. Magnesia-Kainit Slurry Sulphur deficiency can be avoided with the use of fertilisers containing Magnesia-Kainit, Korn-Kali or ESTA Kieserit gran. Sodium Palatable forage means higher intakes Sodium is often at low levels in UK soils and therefore forage tends to be low in sodium also. Livestock, particularly ruminants, have high demand for sodium and a dairy cow has a typical requirement of some 15 2 g/day. Adequate sodium is also required for cow fertility and if the K:Na ratio is greater than 2:1 in forage metablic disorders and fertility problems can result. With a diet deficient in sodium, cows react with marked increase in production of the hormone aldosterone. This hormone is responsible for regulating sodium in the animal but is also important for fertility and studies have shown a direct correlation to low sodium and fertility problems. White clover Trifolium repens A wild and cultivated creeping legume very commonly found in pasture. A 2 3% clover inclusion in a sward can fix upto 18 kg/ha N but is particularly sensitive to low P and K status.

13 13 What happens if the cow gets insufficient sodium? Problem: lack of sodium in the diet Result: low blood sodium stimulates adrenal gland to produce aldosterone 1 Aldosterone to the kidney Aldosterone formation Falling Na level in saliva The cow can regulate sodium at three points in the body: 1 in the kidney 2 in the colon and 3 in the saliva. Low Na in these points stimulates the adrenal cortex to produce aldosterone 3 Aldosterone to the saliva gland Na is increased in the blood 2 Aldosterone in the colon Result: Na excreted in the dung and urine decreases K:Na ratio is crucial for good fertility The potassium level in the forage can be influenced by weather, use of manures or fertilisers and water status at cutting. The following points should be noted: The actual K content of the forage is of less importance than the ratio to other minerals, particularly magnesium and sodium The use of lick-stones, cattle salt, and salt added to the ration has physiological limitations and carries a risk of inducing diarrhoea The sodium content of forage is inherently poor and the critical K:Na ratio of 2:1 is rarely achieved with the use of sodium-free fertilisers. Magnesia-Kainit enriches sodium in the forage and improves the mineral balance through delivery of magnesium, potassium and sodium in a ratio that promotes healthy mineral nutrition of the livestock. K:Na ratio in forage after application of Magnesia-Kainit in 6 different years With Magnesia-Kainit 14 :1 21:1 23:1 18:1 17:1 16:1 Without Magnesia-Kainit 38 :1 75 :1 74 :1 33 :1 5 :1 25 :1 Meadow fescue Festuca pratensis Important perennial forage species forming large tufts. Prefers heavy soil types

14 14 Sodium makes forage more palatable Increased levels of sodium in forage have been proven to increase the palatability of the forage. Studies at the University of Wales found that cows grazing pastures treated with 64 kg/ha sodium had higher forage intakes leading to 15% increase in milk yield with higher protein, butterfat and lactose An additional.32 kg/day increasse in liveweight gain Forage intake by beef steers increased by 29% Rumen ph was effectively buffered for more efficient digestion The clear improvement in forage palatability results in higher biting rates, longer grazing times and less grass rejection. Grass is also grazed tighter and therefore can be utilised more efficiently. More palatable grass means more palatable silage too and cows show a preference for 'tasty' silage enriched with sodium. Daily forage intake (DM/cow) Forage intake and milk yield after treatment with sodium fertiliser NIL 32 kg Na/ha 64 kg Na/ha Forage intake (kg DM/day) Daily milk yield Source: Chiy, Phillips, University of North Wales Milk yield l/day/cow More grass is utilised after treatment with Magnesia-Kainit remaining grass in meadow % Red Clover Trifolium pratense Short lived perennial used as a green manure for its N-fixing ability. Very sensitive to low P and K. Source: Diplomarbeit TU Weihenstephan % Control 6% Magnesia-Kainit

15 Potash, magnesium, sodium and grass staggers reviewing the facts 15 A recent report from the Professional Analysis Advisory Group (PAAG) found that 45% of all soil analysis samples from livestock farms were below target index 2- for potash and therefore at risk of missing out on vital yield. It appears that there is a nervousness about applying potash onto grassland becasue of a fear of increasing the risk of inducing hypomagnesaemia (grass tetany or 'staggers'). Grass staggers is a highly debilitating metabolic disorder but it might be useful to consider the facts and the principal causes of this condition. Hypomagnesaemia literally means 'low blood magnesium' and is most commonly seen around turnout in Spring when forage tends to be rich in potassium and poor in Mg and Sodium. Why is sodium important? Sodium is important because in the absence of sufficient sodium, stock will absorb higher K levels which can hinder Mg absorption from the feed. suggests that this concept is only true when K is measured as a function of DM. If K in fresh herbage is measured, the level is more constant through the year and the higher K figures are purely a result of a higher water content in rapidly growing spring grass. What can be done to lower the risk? Secure an adequate supply of Magnesium Maintain minimum of Mg index 2 in soil Using only water-soluble magnesium fertilisers (ESTA Kieserit, Magnesia-Kainit) Supplementation of stock with Mg through boluses, injections or in feed (costly) Always ensure grassland receives sodium in the fertiliser to maintain the balance of nutrients in forage (target less than 2:1 K:Na ratio). For grazed fields, avoid dressings of potash in the Spring (see RB29 for specific advice on suggested timings). What is luxury uptake? So called 'luxury uptake' is the taking up by plants of excessive levels of K above that required for normal growth. New thinking within the International Fertiliser Society however Target in DM Potassium Magnesium Sodium 2.5% >.2% >.5% Crucial rations of minerals in forage Potassium: Sodium Less than 1:1 to 2:1 target for healthy grass and animals 2:1 to 5:1 Increasing risk of staggers Potassium:Magnesium Less than 2:1 target for healthy grass and animals over 2:1 Increasing risk of staggers The relationship between staggers and sodium content of forage % incidence of staggers Sodium in forage (% DM) Sodium Source: Potash development Association J. Agric. sci 1963

16 Fertiliser range for grass 16 EC FERTILISER Crude potash salt 11( ) Magnesia-Kainit is the perfect grassland fertiliser with four key nutrients for grass and healthy livestock. Magnesia-Kainit can be applied as a straight or can be blended with other nutrients and is tested to spread upto 36 m. Suitable for use in organic agriculture*. 11 % K 2 O water-soluble potassium oxide 5%MgO water-soluble magnesium oxide 27 % Na 2 O water-soluble sodium oxide 1 % SO 3 water-soluble sulphur trioxide (= 4% S) EC FERTILISER Potassium chloride containing magnesium salts 4 ( ) 4% K 2 O water-soluble potassium oxide 6% MgO water-soluble Magnesium oxide 4% Na 2 O water-soluble sodium (3% Na) 12.5% SO 3 water-soluble sulphur trioxide (5% S) Korn-Kali is ideal for highly productive silage or hay fields. With a balanced analysis and higher potash to replace the larger K offtake from conserved grass. Korn-Kali can be applied as a straight or can be blended with other nutrients and is tested to spread upto 36 m. EC FERTILISER Kieserite % MgO water-soluble magnesium oxide 5% SO 3 water-soluble sulphur trioxide (2% S) ESTA Kieserit is the prefect fertiliser for supplying immediately available water soluble magnesium and sulphur for grass and forage crops. ESTA Kieserit can be applied as a straight or can be blended with other nutrients and is tested to spread upto 48 m. Suitable for use in organic agriculture*. * Magnesia-Kainit and ESTA Kieserit are suitable for use in organic agriculture according to EU directives 834/27 and 889/28 and have been certified by the Soil Association.

17 17 On our website, you will find details of the complete fertiliser product range with specialist advice and information on how to get the most from your grassland. You can also find results of field trials and view a gallery of pictures of nutrient deficiency symptoms. Further information materials can be ordered online or by telephoning the freephone number below. Specific recommendations can also be tailored for you by our FACTS certified techncial manager. For contact: Helpline Freephone info@ks-ukeire.co.uk K+S UK & Eire Ltd Unit 13 Watermark Way Foxholes Business Park Hertford SG13 7TZ UK

18 Notes:

19

20 K+S UK & Eire Ltd. Unit 13, Watermark Way Foxholes Business Park Hertford SG13 7TZ Tel Fax A K+S Group Company 7559/1214/w/englisch/NH = Registriertes Warenzeichen der K+S KALI GmbH Technical Helpline Freephone