Cilthrew Project Update - October 2023

The project is taking place in a single 3ha (7.4 acre) field, known as ‘Mynydd Bach’.

The field’s characteristics vary but are generally as follows: 

• east facing
• loam soils, shallow in places 
• altitude ranging from 124m (406 feet) at lowest point, to 175m (574 feet) at the highest point.
• slope gradient varying throughout the field, 62.5% at its steepest as seen in Figure 1.
• un-stoned track running across the middle of the field, from east to west

Figure 1. Ordnance Survey topography map (Mynydd bach centred).

Soil analysis

Soil analysis results from November 2022 for the whole of Mynydd Bach field (Table 1) was used by farm consultant Marc Jones to provide nutrient recommendations to correct pH, P and K indices as required during the project as detailed below. Ground calcium agricultural limestone was applied to the whole field at a rate of 5 t/ha (2 t/ac) in the spring of 2023 which should have been adequate to increase the pH level to 6.2 which is adequate for grass and clover leys. 

Table 1. Mynydd Bach soil analysis results and recommendations from November 2022
 

Project treatments

Six treatments have been established, consisting of 3 different seed mixtures and each mixture trialled with and without mycorrhizal fungi and rhizobacteria.

The product containing arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria (PGPR) was mixed with the seed before sowing. This product aims to increase N and P availability while also enhancing drought tolerance. In limited trials this has shown a yield increase of up to 25% in grass leys.

The treatments and ley types that are being trialled are as follows in Figure 2.

Figure 2. Details of ley type and treatment

Seed mixtures

Details of the varieties included in the above seed mixes are available in Table 2a, 2b, 2c, 2d, 2e and 2f.

Table 2a. T1; traditional PRG and clover ley

 Table 2b. T2; legume and herb mix (no grass)

Table 2c. T3; diverse multi species ley

Table 2d. T1+; Traditional PRG and clover ley + Mycorrhizal fungi and rhizobacteria mix (SR2)

Table 2e. T2+; legume and herb mix (no grass) + SR2

Table 2f. T3+; diverse multi species ley + SR2

Field layout 

Due to the variation of characteristics within the field, a randomised block design, as seen in figure 3 has been used to ensure a fair trial, with all 6 treatments being replicated 3 times across the field. Each plot is a minimum of 0.0729 ha (27m x 27m squares) with a minimum of 2m buffer zones between each plot in order to avoid fungi or bacteria spreading from the treated to untreated plots.  

Figure 3. The 18 plot areas layout

Initial whole field assessment

Soil assessment following the VESS methodology and earthworm counts were carried out prior to establishing the crop to provide a baseline on soil assessment and biology on 21/08/23.

Crop establishment

For crop establishment the following actions were undertaken: 

1. 2 September 2023 - Current pasture destroyed using Glyphosate at recommended rate.
2. 7 September 2023 - Areas with longer grass and thatch mown to reduce the amount of decaying plant material that would lower surface pH.
3. 7 September 2023 - Tine harrow used to remove thatch and mown grass. 

4. 13 September 2023 - Fertiliser applied for establishment at 400kg/ha of 15:15:15 together with 50kg/ha of Triple Superphosphate (TSP 47%)

5. 14 September 2023 - Seed direct drilled at recommended seed rate for each plot area (detailed in Figure 2), along with slug pellets at recommended rate using Moore Uni-drill.

6. 14 September 2023 - Cambridge roller used for consolidating to ensure good soil to seed contact

Although all plots seemed to establish well initially, a change in the weather brought colder temperatures and high rainfall in October 2023, slowing growth.