Effects of adding form and proportion of cassava residues in soilless cultural substrate on the fruit yield and quality and antioxidant capacity of tomato

Objectives In order to reduce the substrate cost of peat, we studied the availability of replacing partial peat with cassava residues, which could help finding a cost effective way for the recycle of cassava residues.

Methods Cherry tomato cultivar of ‘Qianxi’(QX) and large tomato cultivar of ‘Chuanqi 2’ (CQ) were used to carry out a soilless trough experiment. Four substrate formula were made, including peat∶vermiculite∶perlite∶powdery cassava residue = 5∶5∶5∶5 (T1), peat∶vermiculite∶perlite∶granular cassava residue = 5∶5∶5∶5 (T2), peat∶vermiculite∶perlite∶granular cassava residue = 6∶4∶4∶6 (T3), peat∶vermiculite∶perlite∶powdery cassava residue = 4∶4∶4∶8 (T4), and the conventional formula of peat∶ vermiculite∶perlite = 10∶5∶5 was used as control. The physical and chemical properties of the substrates were measured. The growth, yields and fruit qualities were analyzed.

Results The stem diameter, roots activity, and shoot and root dry weight of CQ and QX under T1 and T4 treatments were significantly larger than CK, and the increment under T1 treatment was more than that under T4 treatment. The fruit quality and antioxidant capacity of tomatoes under T2 and T3 treatments were significantly higher than CK, and the increment under T2 treatment was more than T3 treatment. Compared with CK, the soluble sugar, soluble solid, sugar-acid ratio, Vc, lycopene, soluble protein and total phenol contents in CQ and QX fruits were increased by 42.5%, 29.4%, 26.7%, 21.0%, 25.1%, 51.1%, 17.1% and 28.0%, 26.3%, 19.4%, 46.0%, 22.4%, 19.0%, 25.8% under T2 treatment, and the total antioxidant capacity and the scavenging ability of DPPH in CQ and QX fruits were increased by 51.9%, 44.0% and 40.4%, 72.4% respectively. The yields of CQ and QX under T1 treatment were significantly higher than under the other treatments, and were 15.6% and 33.7% higher than under CK. Comprehensive evaluation of two tomato varieties showed an order of T1 > T4 > T2 > T3 > CK.

Conclusions Adding both powdery and granular cassava residues could increase the pH, EC, bulk density and the contents of available N, P and K, and the increment with granular cassava residues are higher than with powdery cassava residues. The good effects on yield and fruit quality are significantly higher with the two formula of replacing half peat (T1 and T2) than with the other two. The best fruit quality could be obtained under T2 treatment, and the highest yield increase under T1 treatment. According to comprehensive evaluation of DTOPSIS, the formulation with peat∶ vermiculite∶perlite∶powdery cassava residue = 5∶5∶5∶5 (T1) is recommended for tomato soilless cultivation.