Alternative fertilisation for processing tomato in Southern Italy.

Two field trials were carried out in Foggia (Southern Italy) in 2002 and in 2003 on a silty-clay soil for evaluating the effect of three organic fertilisers on yield and quality of tomato for processing. The treatments were: 1) organic biological fertiliser (ORG), 2) experimental compost composed of olive residues, sludge and straw (COMP), 3) organic fertiliser mixed with ammonium nitrate (1:1) (MIX), and 4) traditional chemical fertiliser (ammonium nitrate, MIN). All were applied on a 100 kg N ha-1 basis. At harvest, total and marketable fresh and dried yield were measured as well as shoot biomass. N content in the soil and in the shoot tissues was assessed in order to evaluate the N mineral deficit and to calculate N use efficiency (NUE). Meanwhile in the first year no differences were observed among fertiliser treatments, in the second year the ORG fertiliser yielded more than MIX and MIN treatments. The COMP fertiliser showed an intermediate behaviour. No effect due to the fertilisers was observed on fruit quality. The N deficit was positive for the MIX treatment in both years, while in the second year ORG and COMP fertilisers showed negative values and greater N uptake. Higher values of NUE were observed for the MIX treatment in both years