Researchers have found that reducing the amount of synthetic fertilizer used in pineapple production increases crop yields while maintaining soil quality and lowering greenhouse gas emissions, according to a recent Chinese study. Gradual and decreased fertilizer application in combination with the incorporation of organic fertilizers, serve as beneficial for both pineapple growth and the environment.

Pineapple is beloved as a nutritious and delicious fruit, primarily grown in the tropical regions of South America and Asia. The overreliance on synthetic fertilizers in pineapple production is damaging to both soil and air, draining the soil of its nitrogen compounds and causing the emission of nitrous oxide, a potent greenhouse gas. Synthetic fertilizers use inorganic materials, quickly applied and absorbed by soil, while organic fertilizers facilitate nitrogen production via the microbes of the soil and have fewer detrimental effects on soil and climate change.

In this study, researchers sought to examine the impact of fertilizer amount, application schedule, and type (synthetic, organic) on pineapple yield, as well as the economic and environmental benefits. Over two seasons researchers applied five different treatments to fields of pineapple plants:

• control, with no fertilizers
• full synthetic fertilization
• reduced synthetic fertilization
• reduced synthetic fertilization with partial organic substitution
• reduced synthetic fertilization with partial organic and slow-release fertilizer substitution

Crop yield, greenhouse gas emissions, and nitrogen loss were measured for each season.

Pineapple yield was highest when using reduced synthetic fertilizer, organic substitution, and slow application, 26.3% higher than the group that fully applied synthetic fertilizer. This yield increase was greater in the second season, which suggests that the beneficial effects in the soil can accumulate over time. The lowest yield occurred in the group without any fertilizer, and the second lowest in the group that fully applied synthetic fertilizer.

Nitrogen use efficiency–the percent of nitrogen utilized by the pineapple plants–was highest in treatments that incorporated organic fertilizer, 75.5% and 87.7% higher than full synthetic fertilization with and without slow-release, respectively. When synthetic fertilizer was heavily applied, large portions of it were washed away by water–a process known as nitrogen leaching–and another significant portion was converted into nitrous oxide gas and emitted into the atmosphere.

Greenhouse gas emissions were highest when synthetic fertilizer was fully applied, and lowest with no fertilizer at all, with the absence of fertilizer eliminating 58% of emissions. The use of organic fertilizer decreased greenhouse gas emissions by 29% and 27% with and without slow release respectively. These emissions were even compared to the reduced synthetic fertilizer group, at 12% and 10% respectively. Instead of inputting extraneous nitrogen, organic fertilizers stimulate soil microbes to convert existing soil nitrogen into usable compounds, thereby reducing nitrogenous gas byproducts.

This study does not include a treatment that exclusively used organic fertilizer. Although the higher cost of organic fertilizer can be a barrier for use by farmers, this study shows promising results in terms of possible yields and environmental effects in their exclusive application. These encouraging trends need further investigation in other crops and regions to see if the results are replicable.

Overall, this study shows that reducing synthetic fertilizer use is beneficial to pineapple farming, both economically and environmentally. With fertilizer reduction, farmers reduce input costs while also increasing pineapple yield. Furthermore, the environmental impacts cannot be underestimated—reducing fertilizer use helps cut down greenhouse gas emissions on a global scale while preserving soil nutrients on the scale of the field.

Photo by Avrielle Suleiman; https://unsplash.com/@elleirva