Optimum range of twelve tomato cultivars: I. Macronutrients

Responses to macronutrients are compared in tomato (Lycopersicon esculentum Mill.) cultivars (Bufalo [control, a widely cultivated variety in Southern Spain], Corindon, Dombelo, GC-773, GC-775, Nancy, Nea, Sarky, Yunque, Volc ani, 617/83 and 2084/81) grown in controlled greenhouse conditions, were de termined and compared. The following parameters were considered: organic N, NH4, NO3, total and inorganic P; total and soluble Na, K, Ca, Mg; total S and SO4; Cl, endogenous nitrate reductase activity (NRAe), aminoacids and s oluble proteins. Optimum ranges were calculated from yield and plant analys es figures. Those cultivars registering high yields [and therefore attracti ng our attention] demanded varying rates of nutritional applications, so th at their optimum ranges differed. Accumulation of NO. in the leaves (which reduces foliar CI- and seriously affects fruit quality) in all cultivars, i s explained by the greater affinity of the conductive tissue for NO3 over C L. NH, accumulation in the leaves alters pH and may be one cause of high ni trate concentration. High concentrations of mineral N were found in the lea ves of all cultivars and were due to the stronger application of nitrate th an ammonium.