Soil-applied nitrogen uptake by young olive cultivars intercropped or not with Paspalum notatum

Nitrogen (N) applications can be made in orchards to meet the N demand of the olive tree (Olea europaea L.), which may differ between cultivars. But part of the N in the fertilizer may be taken up by ground cover plant species, which can be native, such as Paspalum notatum (P. notatum), derived from the Pampa biome in South America and present in olive orchards. The study aimed to evaluate the recovery and distribution of N fertilizer by olive cultivars, grown alone and intercropped with P. notatum. Young plants of olive cultivars 'Arbosana', 'Coratina' and 'Picual', with and without intercropping with P. notatum, were grown in pots with sandy soil for 16 months. Urea enriched with 10% excess atoms of 15N (0.32 g N vase-1) was applied. Dry matter production and total N and 15N values in soil and plant organs were evaluated. Photosynthetic and chlorophyll a fluores-cence parameters were determined. Fertilizer-derived N (Ndff), soil-derived N (Ndfs) and fertilizer-derived N recovery were calculated. The highest values of recovery of applied N were observed in the organs of olive trees grown without the presence of P. notatum. Ndff applied to the soil surface was accumulated mainly in the leaves and roots of olive trees. The recovery of applied N in cultivars 'Arbosana', 'Picual' and 'Coratina' were low, not exceeding 15% of the N supplied. P. notatum showed a great ability to compete with olive trees for mineral forms of N available in the soil. This is because it decreased growth and N in organs of the olive cultivars.