The use of pineapple liquid waste and cow dung compost to improve the availability of soil N, P, and K and growth of pineapple plant in an Ultisol of Central Lampung

A study that was aimed to elucidate the effect of adding pineapple liquid waste and cow dung compost in increasing the availability of soil N, P, K, contents of N, P, K in pineapple leaves and growth of pineapple plant in an Ultisol was conducted in Central Lampung. The study consisted of two steps, i.e. incubation of pineapple liquid waste with cow dung compost in the soil, and planting pineapple by adding pineapple liquid waste and cow dung compost. Treatments tested in experiment 1 (laboratory incubation experiment) were combinations of pineapple liquid waste (L) and cow dung compost (K). Changes of soil chemical characteristics were observed at 15, 30, 45, and 60 days. Three best treatments of experiment 1 were selected for the experiment 2 (plant growth experiment in a glasshouse). Two control treatments were included in experiment 2. N, P, and K contents in pineapple leaves as well as and pineapple root length were observed at 30 and 60 days. Results of the first experiment showed that addition of pineapple liquid waste and cow dung compost significantly increased soil pH, availability of soil N, P, and K compared to controls at 15, 30, 45, and 60 days. Addition of 20 t cow dung compost/ha and 20,000 L pineapple liquid waste/ha (K3L3 treatment) resulted in higher values of soil pH, total N, available P, and available K than the control. Results of the second experiment showed that the addition of pineapple liquid waste and cow dung compost gave no significant effect on the growth of pineapple plant, but the addition of 20 t cow dung compost/ha and 10,000 L pineapple liquid waste/ha (K3L2 treatment) gave optimum growth compared to other treatments at 60 days. The  K3L2 treatment also had higher pineapple leaf nutrient content, compared to control.