Effect of different reduced fertigation modes on the yield, quality and economic benefits of honey pomelo

Abstract: 【Objective】In this paper, the effects of different reduced fertilization modes on the yield, qual-ity and economic benefits of honey pomelo were studied through three years test (2016—2018) in order to provide the theoretical basis for the reduction of fertilization .【Methods】In this experiment, 5 irriga-tion and fertilization modes were set up: no fertilizer (CK); traditional fertilization (TF); reduce 30% of fertilization during the top dressing period under burring application of slow controlled release fertilizer (SCR); reduce 30% of fertilization during the top dressing period by sprinkling tape fertilizer (DSF); re-duce 30% of fertilization during the topdressing period by drip irrigation and fertigation (DDF). The test-ed fertilizers were as follows: 1) traditional fertilization treatment, according to the local farmers’hab-its: urea (N 46%), calcium superphosphate (P2O5 12%), potassium sulfate (K2O 50%); 2) Controlled re-lease fertilizer was a special formula controlled release fertilizer (base fertilizer N∶P2O5∶K2O = 10∶6∶10; the flowering stage, N∶P2O5∶K2O = 20∶10∶10; young fruit stage, N∶P2O5∶K2O = 20∶10∶15; the vigor-ous fruit stage, N∶P2O5∶K2O = 15∶15∶20). The controlled-release nitrogen was resin coated urea with ni-trogen content of 43%, and the controlled-release period of 60 days. The phosphorus and potassium in  the formula were monoammonium phosphate and potassium sulfate, respectively. 3) Urea (N 46%), po-tassium dihydrogen phosphate (P2O5 52%, K2O 34%) and total water-soluble potassium sulfate (K2O 50%) were selected as nitrogen fertilizer for sprinkler belt and drip irrigation.【Results】The application of drip irrigation and fertilization technology could improve the quality, yield and economic benefitsin the honeypomelo. (1) The effects of 4 fertilization modes on the average yield of the honeypomelo in 3 years was DDF > DSF > SCR > TF. Compared with TF mode, the average yields of the honey pomelo in the SCR, DSF and DDF modes were increased by 13.20%, 19.00% and 24.67%, respectively. There were significant differences between the three models and the TF model; the average yield of the DDF model was 10.38% higher than that of the SCR model, and the difference between them was significant; the yields of the DDF model in 3years were 4.74%, 6.10% and 3.51% higher than those of the DSF mod-el, with an average increase of 4.79%. The results showed that the effect of the integrated mode of water and fertilizer on improving the average yield of the honey pomelo was better, the drip irrigation fertiliza- tion mode had a certain increase effect on the yield of the honey pomelo. Compared with the TF mode,the average commodity rate of the SCR, DSF and DDF increased by 2.48%, 7.59% and 9.18%, respec-tively. The three-year average second class fruit rates of the SCR, DSF and DDF modes were 11.36%, 6.97% and 5.71%, respectively. The results showed that drip fertilization, sprinkler fertilization and slow controlled release fertilization could improve the marketability of the honey pomelo, and the effect of drip irrigation was the best. From 2016 to 2018, the treatments of the SCR, DSF and DDF significantly increased the single fruit weight and pulp weight compared with the TF mode. The average fruit crack-ing rates showed the following trend: the TF (11.97%) > the SCR (11.30%) > the DSF (9.27%) > the DDF (7.93%). Different fertilization patterns had no significant effect on peel weight and flesh granula-tion rate. Drip irrigation and fertilization (fertigation) significantly improved the basic agronomic traits,increased the single fruit weight and reduced the cracking rate. (2) The partial factor productivity showed an increasing trend year by year. The highest partial factor productivity was the DDF mode, which was increased from 22.73 kg·kg^-1 in 2016 to 36.50 kg·kg^-1 in 2018, with an increase of 60.56%, compared with the TF, SCR and DSF modes, the average partial factor productivity in three years was in-creased by 12.72 kg·kg^-1, 4.17 kg·kg^-1 and 2.06 kg·kg^-1, respectively. The reasonable fertilization mode was beneficial to increase the yield of the honeypomelo and the agronomic utilization rate of fertilizer, while the effect of drip irrigation was the best. (3) The DDF mode was in favor of improving fruit weight, pulp weigh and decreasing fruit cracking rate, and to a certain extent, it could improve the con-tents of soluble sugar, sugar /acid and vitamin C, and reduce the titratable acidity of the honey pomelo.There was no significant difference among different fertilization patterns, the DDF was the best, the DSF was the second; (4) The average input cost of the DDF mode was 60 522.9 Yuan·hm^-2, saving 7 473 Yuan· hm^-2, 7 383.8 Yuan· hm^-2 and 2 502.7 Yuan· hm^-2 respectively compared with the TF, SCR, DSF modes. And the output of the DDF mode was high, the proportion of commodity fruit was large and the comprehensive production efficiency was significantly improved, the average net income was 47.79%, 27.13%, 7.68% higher than the TF, SCR and DSF respectively. And the average input-output ratio of the DDF mode was the highest (4.29∶1), which was 1.31 times higher than that of the TF mode.【Conclusion】According to the parameters of the honey pomelos’yield, partial factor productivity, agronomic characters, quality and economic benefits, drip fertilization was an ideal way of irrigation and fertiliza-tion in the honey pomelo production. The drip irrigation and reduced fertigation method was of great sig-nificance to improving yield, economic benefits, quality and sustainable development in the honey pome-lo orchard.