Influence of Compost Amendment on Tomato Vegetative Growth and Photosynthetic Pigments under Greenhouse Conditions in Mardan, Pakistan

The effects of compost amendments on the vegetative growth and photosynthetic pigment content of Solanum lycopersicum (tomato) were studied in a controlled greenhouse environment. The tomato seeds grew in the soil that is 67% by volume a traditional soil and 33% a compost soil, that is 33% of the soil is composed of compost, the remaining soil is traditional soil, for comparison, a group of tomatoes were also planted in purely traditional soil (100%). The observations after two months included changes in the growth level of plants (architecture of the root system), plant biomass (fresh and dry weight), plant leaves count, branching and changes in the content of chlorophyll pigments. The observations were made in the greenhouse of the department of life sciences Abdul Wali Khan University Mardan, Pakistan from January to March 2023. The relative humidity (RH) was maintained at 85% during both day and night, and the atmospheric temperature was 22°C for the day and 18°C for the night in the greenhouse. Independent-samples t-tests revealed that there were statistically significant differences between the compost amended soil group and the control group for the following growth measurements: Light green foliage area, Light green leaf area, and root weight. In particular, the control group had significantly less fresh root weight (t = 4.93, p = 0.039), dry shoot weight (t = 5.18, p = 0.035), and leaf count (t = 5.56, p = 0.031) compared to the experimental group. The spectrophotometric data on spectrophotometric absorptions of four groups of photosynthetic pigments revealed that in most of the soil groups the absorption was significantly higher than that in control (p < 0.05). Chlorophyll-a (663 nm) increased 89%, and chlorophyll-b (645 nm) by 136% compared to the control. There was a 107% and 518% increase in the carotenoid group (470-480 nm) and xanthophyll (518 nm) stain, respectively, over control. This was observed in all the measurements which suggested that the plants treated with compost have more photosynthetic pigment which in turn translates to improved light collection. The reviewed part of the study includes the effect of organic amendments on soil physicochemical properties, nutrient cycles, water retention and microbial activity as environmental studies have been observed all around the world. In the context of the semi-arid environment of Mardan, Pakistan, the body of evidence indicates that compost can be used as an eco-friendly agro-modifier that can enhance agro productivity.