The effect of potassium fertilisation on yield, nutritive value and K, Ca, P and Mg concentration in perennial ryegrass | Vpliv gnojenja s kalijem na pridelek, hranilno vrednost ter vsebnost K, Ca, P in Mg v trpezni ljuljki
2009
Babnik, D., Agricultural Inst. of Slovenia, Ljubljana (Slovenia) | Verbic, J. | Susin, J. | Verbic, J. | Znidarsic, T.
The effect of fertilisation at nine different levels of potassium (K) fertilizer (from 0 to 400 kg K2O ha-1) on the concentration of ammonium acetate lactate extractable potassium (available K) in soil and, consequently, the effect on yield, nutritive value, concentration of K, Ca, P, Mg in perennial ryegrass of the first and second harvest was studied. At the first and second harvest the highest dry matter yield was obtained at the concentration of 16 mg available K2O per 100 g soil and/or at the concentration of 24 g K per kg of dry matter (DM) in grass and/or at 50 g K per kg DM of cell content. With a higher level of K fertilizer applied, when K available in soil was increasing, the DM yield at the first harvest decreased. There was no great change in nutritive value but high increase of K concentration and decrease of Ca and Mg in grass were observed. An unfavourable ratio of K/(Ca+Mg) which implies an increased risk for grass tetany (2.2 mEq) was arisen when K available in soil increased above 40 mg K2O and/or K in grass increased above 30 g kg-1 DM. Significant (p0.05) negative DM yield response could be expected at available K concentration below 10 mg K2O per 100 g of soil, i.e. when K concentration in grass decreases below 15 g K per kg DM and/or K concentration in cell content decreases below 35 g per kg DM. It could be concluded that prediction of K requirements for grassland or for fertilizer planning based on K concentration in forage as an indicator of supplying grass with K would be an important improvement instead of using only soil available K analyses.
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