Effects of Black Pepper-Groundnut Intercropping on Soil Total Nitrogen and the Physiological Characteristics of Black Pepper (Piper nigrum L.)

Abstract

The utilisation of leguminous groundnut (Arachis hypogaea) has been recognised for its advantageous
effects, including nitrogen (N) fixation, which consequently enhances the soil N availability. The objective
of this study was to analyse the impact of a mixed intercropping system involving pepper (Piper nigrum)
and groundnut on soil total N. Additionally, the study aimed to assess the influence of N on various
parameters, including the Normalised Difference Vegetation Index (NDVI), chlorophyll content, and gas
exchange rate of black pepper. The study employed a randomized complete block design in a field
experiment, with two treatments that were reproduced 15 times. The treatments consisted of the control
group (M0), which involved a pepper plot without groundnut intercropping, and the mixed intercropping
system (M1), which involved a pepper plot with groundnut intercropping. The soil total N content exhibited
a statistically significant increase (p < 0.05) in the context of a mixed intercropping system. The
intercropping treatment resulted in considerably higher values (p < 0.05) for pepper NDVI, foliar
chlorophyll concentration, photosynthetic rates (A), stomatal conductance (gs), and transpiration (E)
compared to the control treatment. Moreover, a positive correlation has been seen between the chlorophyll
content of pepper leaves and the total N content in the soil. Similarly, a positive association has been
established between the A of pepper plants and the total N content in the soil. As a result, the observed
elevation in A under high N circumstances was ascribed to an augmentation in chlorophyll concentration.
Consequently, the integration of groundnut within pepper cultivation systems over an extended period has
the potential to enhance crop productivity through the amelioration of soil conditions.