Out of Africa – Kikuyu Management for ME, Production and Profit

Two great summaries of the early work of the Kikuyu Action Group for you to read and download here:

Introduction

Kikuyu is among the four most important pasture species in northern dairy pastures (the others being ryegrass, poa annua and white clover). It continues to spread in Northland and in other coastal areas of New Zealand.

Kikuyu is a controversial plant. Love it or hate it, once established it has to be carefully managed to achieve maximum production.

The Northland Kikuyu Action Group is a farmer-based group, formed in 1999. Up to 2004 research aimed to provide a “tool box” of options for farmers to improve the management of, and returns from, kikuyu-dominated pasture, according to their policies and individual circumstances.

A key objective of the group is to increase the quality (Metabolisable Energy) and dry matter intake of dairy cows during winter and spring. Trial work was designed and carried out by an independent science provider on high-fertility, flat land dairy farms. Trials were based on large plots within paddocks subjected to normal dairy grazing management. Results were obtained from farms near Whangarei, Dargaville, Kerikeri and Kaitaia. Recommendations may have to be modified in other regions.

KAG has now moved on to trialling methods for eradication of kikuyu. This research is still underway.

Ryegrass vs Kikuyu
To understand Kikuyu management farmers must forget what they currently accept as best practise for ryegrass management.

Ryegrass is a temperate grass used throughout NZ. Ryegrass grows from tillers throughout the year. It is weakest during drought, susceptible to insect attack, and has a high risk of facial eczema.

Kikuyu is a subtropical plant that grows leaf stem and stolons above the ground with some rhizomes below. Its main growth period is January to May, with very low growth (0 to 10 kgDM/ha/day) from July to October.

Roots emerge from the stolons which can effectively become another “plant” if the stolon is cut. A kikuyu pasture is a complex of plants of different ages and maturity. Old plants are resilient to drought and to insect attack. Kikuyu pasture has a lower eczema risk than ryegrass.

Rye grass quality does not change much relative to kikuyu. Even during rye’s seed production phase farmers make good quality hay from seeded ryegrass. Ryegrass can be put onto a long rotation in autumn without losing quality. Kikuyu cannot.
For ryegrass the emphasis on feed availability is on more dry matter. For a ryegrass variety later flowering, good sugar levels and a high digestibility are important breeding objectives. For farmers the most important objective is greater yield. Farmers may get a response from applying nitrogen virtually all year round in Northland to ryegrass.

By comparison, the value of kikuyu varies widely during its growth phase. To maximise production from a kikuyu dominant pasture a farmer must understand how to manage its quality. Keeping kikuyu in a leafy growing state to maximise quality is far more important than managing it for extra dry matter yield. Kikuyu declines in quality as it accumulates more dry matter. The faster it grows the quicker it loses quality. On farms with low stocking rates (Northland dairy farm average is only 2.2 cows/ha) old kikuyu needs to be mulched. Forcing stock to eat it will cause losses in production, condition and liveweight.

Research trials have shown that in some areas kikuyu is at least able to match and sometimes outyield ryegrass in animal production from January to May provided its quality is managed.

Nitrogen should not be applied to a kikuyu dominant pasture from late February to May because this is its most active period of growth. Response to nitrogen can exceed 20 kg DM/ha and the response period last up to 12 weeks from a single application. This results in more mulching being required, increasing management costs.

Fertilising so soil fertility is high is one thing ryegrass and kikuyu have in common in order to maximise production.

Pasture Quality of Kikuyu Pasture
Rather than assessing a kikuyu dominant pasture in terms of kgDM/ha (which will over estimate the potential production off the pasture), it is more useful to use the pasture quality, as measured by ME – metabolisable energy.

An understanding of the changing yield and pasture quality of kikuyu leaf, stem and stolon is vital to maximising production from kikuyu.

Figure 1 shows changes in yield and quality during February- March in Northland.

The work of the Northland Kikuyu Action Group (KAG) has shown farmers how the quality or nutritive value of kikuyu declines as it ages.

Kikuyu over 4 weeks of age is ‘old’ – especially when kikuyu is growing rapidly. By 6 weeks the leaf will be just 9 to 10 ME which is barely productive for milk or growth. By this time the stem is around 8 ME and cattle will only eat the leaf. Because kikuyu fiber takes longer to digest kikuyu stem of this age is less valuable than hay, so for cattle it is barely maintenance. Old stolon at only 7 ME has poor digestibility and its overall nutritive value is so poor that cattle forced to eat it will loose weight. This is the reason mechanical control is required, rather than grazing control.

In December and January kikuyu produces a high ratio of leaf to stem/stolon (70:30). This ratio declines during the season and can be as low as (30:70) in autumn.

Best milk production is from fast-growing green leaf (10-11 ME/kgDM). Stem/stolon can be milked off only when it is green and growing (9-10 ME). Quality declines rapidly in the stem/stolon after two to three weeks of growth (8-9 ME). When kikuyu is on a long rotation the feed quality of the stolon is as low as 7 ME. Cattle cannot maintain themselves on this low quality feed, and will lose weight no matter how much kikuyu they eat.

As kikuyu ages it lays down more fibre which is difficult for cows to digest. (It is estimated to take as long as three weeks for kikuyu stolon to pass through the rumen, compared with one week for ryegrass. Therefore, rank kikuyu should not be fed in the last three weeks before calving, if high peak milk production is to be achieved).

Pasture Utilisation
Because kikuyu has stolons it is more complex than rye grass. The tip of the stolon will have young leaves with high ME value but further down the stolon the leaves are older and of lower ME. If a farmer is on a 21 day rotation and the cows do not eat all the kikuyu, then by the next grazing, the unutilised parts are 42 days old (6 weeks) and only the newly grown leaf is productive. This is how a mat develops – as the cows leave the older leaves at each grazing.

Kikuyu pasture utilisation dropped in relation to the amount of old stem and stolon present. On all the dairy farms that were monitored over a 4 year period by KAG the winter and spring utilisation of pasture dropped as the % of kikuyu in it, and its age increased.

In the KAG trials mulched kikuyu pasture was always utilised down to the level of mulching. Residuals reflected the growth and age of the kikuyu. From April mulching between 60 to 80 % of pasture was utilised during winter and early spring.

In unmulched kikuyu pasture grazed after 6 weeks, only the leaf and stem was grazed. Utilisation was only 30 %. Add to this a reduction of 1 to 2 ME for the older leaf and stem and mulching increased energy utilised during winter and early spring from 39 % (Baxter’s near Kerikeri) to as much as 100 % more energy (Naysmith near Kaitaia).
Important Principles Derived from Northland Kikuyu Action Group Research

• Small paddocks are important in maintaining kikuyu quality. This ensures that sufficient grazing pressure is applied each round to prevent a build up of a mat and maximise pasture utilisation (One KAG trial Farm at Dargaville had paddocks 60 % smaller than all the other dairy farms KAG worked with – and the highest stocking rate (2.7 cows/ha) and production over 800 kg MS /ha)
• Kikuyu is more aggressive and harder to manage on heavy clays, with volcanic soils less difficult, and sandy soils easier
• Mulching to ground level is not recommended on the sands because the topsoil is so thin. Drilling and mowing works well. Neither is spraying roundup on sandy soils recommended, other than for eradication for the same reason
• The most dominant most aggressive kikuyu pasture was north of Kaitaia with Whangarei Heads close behind. Kerikeri was less aggressive on a volcanic soil, and Dargaville the least, relative to the other areas
• Kikuyu dominant pasture cover needs to be low by mid-May (1,00 kgDM/ha) after mulching and sowing annuals in April

Research Results
Plot measurements were made using a non-destructive measurement technique based on 7 to 9 visual assessments per plot (6.2 m x 7m) of % species ground cover, and pasture height before, and after grazing, using an Ashgrove rising platemeter (Average of 30 to 40 readings per plot). Plots were grazed on the same rotation as the rest of the farm.

Samples of kikuyu, ryegrass and white clover were analysed for Nutritive value using NIR (AgResearch Feedtech Palmerston North). Kikuyu was dissected into leaf stem and stolon, ryegrass stem was also dissected out when present.

Kikuyu and ryegrass samples were weighed and dried to determine the dry matter/ha in leaf stem and stolon during autumn, winter and spring.

(See appendix one for comments on the effect of measurement technique).

Key Points:

• Rye and poa were the main winter growers. This was a relatively poor result for mulching, and a good result for spraying
• Spraying significantly reduced kikuyu content in March, especially at the higher rate of 6
• Clover composition was reduced by spraying and the % of bare earth increased

Key Points:

• Ryegrass % in the mulched plots without spraying was still 50 % greater than control after 2 years, and 120 % more for the sprayed plots. Experience suggests the main effect of mulching without spraying is over the first winter and spring unless mulching is repeated each autumn.
• Only the high rate of Roundup had a large reduction in kikuyu content after two years. However with this single autumn spray (grass to grass) kikuyu already covered a third of the area by the second autumn.
• There was a 2 year reduction in white clover % using 6 litres of Roundup.
• Mulching without spraying and using 500 ml of Roundup both increased winter and spring growth potential while leaving kikuyu for summer for those farmers who need it. For farmers wanting to eradicate kikuyu the 6 litre grass to grass programme only gave one year of relief.

Pasture Utilisation

Key Points:

• Average ground cover of kikuyu was 63 % on the 7th of April, before the management treatments were begun. Kikuyu covered 36 % of the control plots by 14 July.
• From the 14th of July to the 14th of October cows only “utilised” an average of 40 % pasture grown on the control plots at each grazing. Pasture growth averaged 45 kgDM/ha/day.
• Kikuyu ground cover was 26 % by 14 July on the mulched and sown plots. Mowing and mulching and sowing annuals increased “utilisation” by 8 % compared to control. Pasture growth rate increased by 38 %. Pasture quality utilised increased by 2 MJME/kg DM.
• Kikuyu ground cover percentage was 0 % by 14 July on both the 1 and 6 plots. Spraying, mulching and mowing and sowing annuals increased “utilisation” by 16% and 14 % respectively. Growth rate increased by 42 %, and pasture quality by 2 MJME/kg DM for both the 1 and 6 treatments.
• Compared to no management cows “utilised” between 1,100 and 1,200 more DM/ha over these critical 3 months, because of the combination of increased growth rate and utilisation.
• In addition ME estimates indicated an overall increase of 1MJME/kgDM from 10 – 11 in the pasture “utilised” between the managed and unmanaged plots.
• Unmanaged plots produced an estimated 44,240 MJME. The mulch/mow plots sown with annual ryegrass produced 62,348 MJME.
• Overall the managed plots sown with annuals produced between 38 – 41% more energy over the winter/spring period.
  Baxter’s farm was producing over 700 kgMS/ha and was not as kikuyu dominant as farms at Kaitaia or Whangarei on clay soils, where the increase could be even greater.
• The “volcanic” soil at Baxter’s made it easier to measure utilisation (disappearance) more accurately than on clay soils because pugging was minimal at each grazing.

Download the attached papers to read further….