NIRS grass and clover

Results:

Perennial ryegrass

There are clear increases in yield due to the additional N.

Dry matter yields (t/ha) from different N levels

Under the conservation management treatments Seagoe was the highest yielding variety under all three treatments with Premium and Rodrigo being the lowest two. There were significant differences between the varieties in the two lowest N treatments in the first year harvests and in all N treatments in the third year harvests but rankings were little changed.

Under the simulated grazing management AberGreen was the highest yielding variety under all treatments. Premium ranked higher under the 100 N treatment than the two higher levels of N. Differences in rank with other varieties were small and not significant.

D values showed no significant difference between 100N and 200N in any combination. However, there was a significant difference between the 400N compared to the 100 and 200N. With higher N levels D values decreased under conservation management in year 1 and increased under the simulated management in year 2.

Generally persistence improved with increasing N levels and there was less weed invasion in swards at the higher N levels. This was particularly noticeable at the Yorkshire site at Headley Hall. This could have a significant effect on the need to re­seed. There were some changes in ranking between varieties although the differences in levels of ground cover were small.

Timothy

As with the PRG there were clear increases in yield due to the additional N. Yield differences between the varieties were small and there were no significant rank changes with the N treatments in comparison with the RGCL figures. As with the PRG the D values declined with increasing N levels under the second cut conservation management in year 1 but not with the first cut or the year 2.

Clover

There were significant differences between grass species in the yields of clover with less clover recorded when grown with Cocksfoot and more when Timothy was the companion species. There were no significant yield differences in the combined grass clover yields in both harvest years. Differences between the varieties used within grass species were small and not significant.

Two varieties of clover were used in the trials, both being medium leaf size types. Yields of Crusader were significantly lower than AberConcord in the second harvest year. Yields of grass and clover were similar with both clover varieties in both harvest years.

The Problem:

NIRS is commonly used to analyse grass silage for dry matter, energy and protein. It has been found in a pilot study funded by HCC that when silage with high levels of clover (white or red) is tested by NIRS the protein level is under-valued by around 2% when compared to traditional wet chemistry methods.

Silage analyses are used to calculate rations, so if NIRS is used there is a possibility of over-supplying bought-in protein as the amount in the forage is not correctly measured. This has implications for feed costs and for the environment.

Project Aims:

• To determine digestibility, dry matter, nitrogen solubility and degradability for a range of 90 grass/clover mixed silages
• To improve the current grass silage NIRS calibration curve to take into consideration high clover levels

Approach:

Around 90 silages, either big bales or clamped, will be collected from dairy, beef and sheep farms in GB with a range of white and red clover proportions. The digestibility will be determined by feeding the silages to sheep, while dairy cows will be used to find out the other parameters.

Deliverables:

Through FAA, the improved grass silage NIRS calibration curve will be disseminated to the forage analysis labs that are involved in their ring test. This means the results will be applied to the industry rapidly.