S13 - Session P2 - Evaluation of threshold values of nutritional indicators in 3 outdoor horticultural crops

Authors: José María Vadillo, carmen Gimenez, Carlos Campillo Torres *, María del Henar Prieto

Economical and sustainable nitrogen management requires good monitoring of the nutritional status of the crop to detect N deficiency or excess. Both optical sensors and nitrate meters are tools to assess the N status of a crop at critical moments by leaf chlorophyll content and sap nitrate content respectively. The nitrogen nutrition index (NNI) is used as a reference for plant N status and calculated as the ratio between %N of the crops and critical %N. The aim of this study is the development of the NNI for broccoli, sweet pepper and tomato crops in the open field and the comparative of this index obtained from measurements of chlorophyll content, measured with MC-100 equipment (Apogge Instruments Inc., Logan, UT, USA) and NO3 content in sap measured with Laquatwin (Laqua Twin Compact Ion Meter, Horiba, Kyoto, Japan). In order to carry out this work, pepper and broccoli were grown in open field following traditional agronomic practices in 2020, and processing tomato in 2021, under different doses of nitrogen fertilisation with the aim of being able to discriminate values of nutritional status measurements. The N doses applied were null (N0), deficient (N1, -50% of N2), conventional (N2) and surplus (N3, +50% of N2) in each crop. Subsequently, the critical curve was calculated for all crops to obtain NNI and compare it with the other nutritional measures.