The most suitable time to sample tagasaste is either between January and March or July and September. The January to March period is only suitable if there has not been significant summer rain. If you are concerned about a mineral deficiency causing visual symptoms on the tagasaste it is best to collect some samples from healthy plants and some from affected plants for a comparison of leaf analysis, which may indicate which mineral is deficient. CSBP Soil and Plant Laboratory is now able to make a recommendation for superphosphate requirements based on the tissue test results. Trace elements Manganese is the only trace element known to limit tagasaste growth, but other trace elements may be necessary for animal production.
Manganese deficiency occurs in tagasaste in similar areas to manganese deficiency in white lupins.
It can be easily identified from the visual symptoms. The deficiency is detected as a yellowing of the plants in winter and spring. A distinctive sign is that not all plants are affected to the same extent, where extensively yellowed plants will be growing right next to healthy ones. There is no good evidence that the application of other trace elements will have an economic benefit to tagasaste growth but several minerals such as copper and zinc tend to occur in tagasaste plants in lower concentrations than generally required for optimum livestock production. If stock are grazing exclusively on tagasaste plantations it may be necessary to supply a trace mineral supplement.