Papaya cultivation on nutrient deficient acidic peat soils causes poor growth, yield, and fruit quality of this crop. Alkalinity and the high affinity of clinoptilolite zeolite (CZ) for macronutrients could improve pH, nutrient availability, and papaya productivity on peat soils. A one-year field experiment was conducted to determine the effects of CZ on: (i) soil ammonium, nitrate, P, and K, and (ii) growth, yield, and fruit quality of papaya grown on a peat soil. Treatments evaluated were: (i) different amounts of CZ (25%, 50%, 70%, and 100% of the existing recommended rate of CZ) + NPK fertilizer, and (ii) NPK fertilizer alone. The peat soils with CZ improved pH, ammonium, nitrate, P, and K availability because of the sorption of these nutrients within the structured framework of the CZ. Co-applying CZ (70% to 100%) and NPK fertilizers improved the NPK contents in papaya leaves and the growth, yield, and fruit quality of papaya because of the significant availability of ammonium, nitrate, P, and K in the peat soil for their optimum uptake by the papaya plants. Ability of CZ to buffer the soil pH reduced the need for liming. It is possible to use CZ to improve papaya productivity because CZ can regulate nutrient availability.

Inappropriate drainage and agricultural development on tropical peatland may lead to an increase in methane (CH₄) emission, thus expediting the rate of global warming and climate change. It was hypothesized that water table fluctuation affects CH₄ emission in pineapple cultivation on tropical peat soils. The objectives of this study were to: (i) quantify CH₄ emission from a tropical peat soil cultivated with pineapple and (ii) determine the effects of water table depth on CH₄ emission from a peat soil under simulated water table fluctuation. Soil CH₄ emissions from an open field pineapple cultivation system and field lysimeters were determined using the closed chamber method. High-density polyethylene field lysimeters were set up to simulate the natural condition of cultivated drained peat soils under different water table fluctuations. The soil CH₄ flux was measured at five time intervals to obtain a 24 h CH₄ emission in the dry and wet seasons during low- and high-water tables. Soil CH₄ emissions from open field pineapple cultivation were significantly lower compared with field lysimeters under simulated water table fluctuation. Soil CH₄ emissions throughout the dry and wet seasons irrespective of water table fluctuation were not affected by soil temperature but emissions were influenced by the balance between methanogenic and methanotrophic microorganisms controlling CH₄ production and consumption, CH₄ transportation through molecular diffusion via peat pore spaces, and non-microbial CH₄ production in peat soils. Findings from the study suggest that water table fluctuation at the soil–water interface relatively controls the soil CH₄ emission from lysimeters under simulated low- and high-water table fluctuation. The findings of this study provide an understanding of the effects of water table fluctuation on CH₄ emission in a tropical peatland cultivated with pineapple.

Pineapple cultivation in nitrogen deficient and acidic peat soils leads to poor growth, yield, and fruit quality of pineapples. A study was conducted to determine whether clinoptilolite zeolite (CZ) could improve soil nitrogen availability, growth, yield, and fruit quality of pineapples grown in drained peat soils. Laboratory leaching experiments were conducted to determine the effectiveness of CZ in controlling nitrogen loss from peat soils, whereas an ion-exchange resin method was used to determine nitrogen availability in pineapple cultivation. Treatments evaluated were: (i) different amounts of CZ (25, 50, 70, and 100%) + NPK fertilizer, (ii) NPK fertilizer, and (iii) peat soil only. The peat soils with CZ reduced ammonium and nitrate losses because of the sorption of ammonium within the lattices of the CZ via ion exchange. Co-application of CZ (25%) and NPK fertilizers was more effective in increasing soil ammonium availability, whereas the use of CZ (25% to 100%) improved nitrogen uptake and use efficiency, growth, yield, and fruit quality of pineapple because CZ could regulate the availability of nitrogen ions for pineapple uptake. The buffering capacity of CZ increased soil pH and facilitated organic nitrogen mineralization. The co-application of CZ and NPK fertilizers can be used to improve nitrogen availability and pineapple productivity in tropical peat soils.

Pineapples (Ananas comosus(L.) Merr.) cultivation on drained peats could affect the release of carbon dioxide (CO₂) into the atmosphere and also the leaching of dissolved organic carbon (DOC). Carbon dioxide emission needs to be partitioned before deciding on whether cultivated peat is net sink or net source of carbon. Partitioning of CO₂emission into root respiration, microbial respiration, and oxidative peat decomposition was achieved using a lysimeter experiment with three treatments: peat soil cultivated with pineapple, bare peat soil, and bare peat soil fumigated with chloroform. Drainage water leached from cultivated peat and bare peat soil was also analyzed for DOC. On a yearly basis, CO₂emissions were higher under bare peat (218.8 t CO₂ ha/yr) than under bare peat treated with chloroform (205 t CO₂ ha/yr), and they were the lowest (179.6 t CO₂ ha/yr) under cultivated peat. Decreasing CO₂emissions under pineapple were attributed to the positive effects of photosynthesis and soil autotrophic activities. An average 235.7 mg/L loss of DOC under bare peat suggests rapid decline of peat organic carbon through heterotrophic respiration and peat decomposition. Soil CO₂emission depended on moderate temperature fluctuations, but it was not affected by soil moisture.

Burning pineapple residues on peat soils before pineapple replanting raises concerns on hazards of peat fires. A study was conducted to determine whether ash produced from pineapple residues could be used to minimize carbon dioxide (CO2) and nitrous oxide (N2O) emissions in cultivated tropical peatlands. The effects of pineapple residue ash fertilization on CO2 and N2O emissions from a peat soil grown with pineapple were determined using closed chamber method with the following treatments: (i) 25, 50, 70, and 100% of the suggested rate of pineapple residue ash + NPK fertilizer, (ii) NPK fertilizer, and (iii) peat soil only. Soils treated with pineapple residue ash (25%) decreased CO2 and N2O emissions relative to soils without ash due to adsorption of organic compounds, ammonium, and nitrate ions onto the charged surface of ash through hydrogen bonding. The ability of the ash to maintain higher soil pH during pineapple growth primarily contributed to low CO2 and N2O emissions. Co-application of pineapple residue ash and compound NPK fertilizer also improves soil ammonium and nitrate availability, and fruit quality of pineapples. Compound NPK fertilizers can be amended with pineapple residue ash to minimize CO2 and N2O emissions without reducing peat soil and pineapple productivity.