Nutrient requirements of forage crops

Yields and nutrient uptake

IRG and PRG/white clover

The Italian ryegrass and perennial ryegrass/white clover swards were cut 3 times in the season (4 times for the IRG in year 2) and produced excellent season yields of 13-15 t/ha dry matter.

Fodder beet

Only the roots of the fodder beet were harvested; the nutrient content of the tops was returned to the soil and has been excluded from the removal figures. If the tops had been recovered the total dry matter production of this crop at 17 t/ha was the highest of all forages. (The nutrient content of tops - higher protein, lower energy - would complement the reverse nutrient balance of the roots.)

Whole crop wheat

The whole-crop wheat yields of 14 t/ha DM compared favourably to the grass yields and involved only a single harvest.

Kale

Good crops of kale were grown, but in the first year, considerable in-field losses were sustained at harvest which were reflected in the poorer average recovered yields compared to the other crops.

Maize

The maize results relate to only a single year and represent only modest performance.

The study confirmed that high yielding forage crops require very large amounts of potash to achieve maximum growth. This emphasises the importance of maintaining adequate reserves of nutrient in the soil - the aim is to maintain soils at index 2 for P and K.

Peak uptake of phosphate and potash in this study were :-

Nutrients taken up by the growing crops