Effect of alkaline slow release nitrogen fertilizer on soil pH and nitrogen use efficiency of banana

ObjectivesLong term and over use of chemical fertilizers has resulted in soil acidification in banana orchards and decline of banana yield and quality. A new type of chemical fertilizer, alkaline slow release nitrogen fertilizer (ALNF,N22%), has been prepared. The purpose of the paper was to study effects of ALNF application on soil pH value, banana yield, nitrogen use efficiency (NUE) and nitrogen losses in the soil.

MethodsTwo field experiments were conducted in banana orchard, one was fertilizer type and the other was dosage comparison experiments. The fertilizer types experiment had four treatments:alkaline slow release fertilizer (ALNF), controlled release fertilizer blend (CRF_BB), conventional fertilizer (CCF) and no nitrogen treatment (CK). The ALNF dosage experiment included following four treatments:completely ALNF (N 337.5 g/plant), ALNF+60 g N from urea (ACF1, 397.5 g/plant), ALNF+90 g N from urea (ACF2, 427.5 g/plant) and no nitrogen control (CK).

ResultsSoil pH value was increased by 1.2, 1.2, 1.1, 0.6 and 0.3 units in the ALNF treatment compared to the CRF_BB, CCF, CK, ACF1 and ACF2 treatments separately under the super high density cultivation of banana. The banana fruit yields per plant in the ALNF and CRF_BBtreatments were increased significantly by 43.4% and 35.1% compared to that in the CCF treatment. The yields of the ALNF and ACF1 treatments were 50.6% and 40.0% greater than that of the ACF2 treatment. In the N balance, the nitrogen uptakes by CRF_BBand ALNF treated banana plants were 48.9% and 24.8% higher than that by the CCF treated plants individually. The highest apparent loss of N was observed in the CCF treatment which was about 2.3 times of that in ALNF treatment. The highest amount of soil nitrogen residual was found in the ALNF treatment, which was about 1.6 and 2.4 times of those in CRF_BBand CCF respectively. The nitrogen absorption by banana in ALNF was 5.0% and 31.9% higher than those of ACF1 and ACF2 individually, while the soil N residual was increased by 60.8% and 162.6%. The nitrogen apparent loss of the ALNF treatment was about one quarter of ACF2. The NUEs of the CRF_BBand ALNF treatments were increased by 66.7% and 33.7% in comparison with CCF individually (P＜0.05). The NUE of ALNF treated banana was 27.8% and 87.7% greater than those of ACF1 and ACF2 treated banana. The NUE of ACF1 treated banana was 46.9% bigger than ACF2 treated one.

ConclusionAlkaline slow release nitrogen fertilizer was proved to be able to increase soil pH values from 0.3 to 1.2 units, to increase banana yields by 35% to 50%, to raise nitrogen uptakes by 24% to 50%, to enlarge N deposit in soil, to decrease nitrogen apparent loss in soil and to increase NUEs by 27% to 67%. Application of ALNF mixed with urea could cause nitrogen apparent loss and reduce the NUE.