Curvas de absorción de nitrógeno y potasio en tomate bajo invernaderos con distintos niveles de fertirrigación

Tomato (Lycopersicom esculentum Mill) is the crop that occupies the largest protected area in Uruguay, with 243 ha according to data from the season 2014/2015 (MGAP. DIEA, 2017) and is the second vegetable in terms of entry into the Mercado Modelo. Crop yields have not increased since the 2002-2003 season (MGAP. DIEA, 2017). These yields are lower than those attainable in the region with similar productive resources and good management. The main yield limiting factors identified for season 2014/15/16 were: potassium nutrition in the first place and nitrogen nutrition for spring and summer crops (Berrueta et al., 2019). In order to improve fertigation management at the farm level, the nitrogen and potassium absorption curves (amounts and moments of absorption) for indeterminate tomato grown in spring/summer under greenhouse conditions in Uruguay were determined in this study. Different levels of nitrogen fertilization (deficient, sufficient and excess) were used. The trial was carried out during spring/summer 2019/20 season at the "Wilson Ferreira" experimental station (INIA, Canelones, Uruguay). Tomato cultivar was Lapataia. The trial consisted in three treatments; T1 without additions of nitrogen and potassium, T2 with addition of 100% of the estimated requirements for nitrogen, potassium, phosphorus, calcium, magnesium and micronutrients, and T3 with addition of 150% of the estimated requirements for nitrogen and 100% of the requirements of the rest of the nutrients. It was observed that T3 was the treatment with the highest accumulation of dry matter with 15694 kg ha^-1, followed by T2 and T1 with 15290 kg ha^-1 and T1 13124 kg ha^-1, respectively. Differences in DM production among treatments were observed from 110 DAT onward and were mainly related to DM in leaves. No statistical differences were found in DM accumulated by the fruits nor in yield. T3 showed the highest N uptake (381 kg N ha^-1), followed by T2 (333 kg N ha^-1) and T1 (289 kg N ha^-1), according to the amount of N available for the different treatments. Potassium uptake was higher for T3 (697 kg K ha^-1), without statistical differences with T2 (652 kg K ha^-1). T1 presented the lowest K uptake (515 kg K ha^-1). At the beginning of growing period nutrients uptake were low and the maximum uptake occurred after 90 DAT due to fruit development. 60% of N and 70% of K were allocated to fruits. N uptake was higher at 120-150 DAT, while K uptake was higher at 90-120 DAT. N and K uptake for T1 were high, even without fertilization, demonstrating that soils with similar characteristics are capable of supply nutrients to maintain high growth rates and high yields. The information generated is key to tomato fertilization planning and improving fertigation management, to increase nutrient use efficiency and contribute to more sustainable systems.