Growth and yield of tomato on soil amended with waste paper based hydrogels

Abstract

Increased water and nitrogen use efficiency enhances crop production and reduces environmental degradation. Cellulosic hydrogels derived from paper waste can retain and gradually release water and nitrogen for plant growth. This study assessed tomato response to water and NO3− − N in soils amended with hydrogels. The experiment was conducted in a greenhouse on a tomato crop, comprising of following treatments: freeze-dried hydrogels (FDH), oven-dried hydrogels (ODH), control (CO) (without hydrogels) as well as two irrigation treatments (95% and 75% available water content (AWC)). The results indicated that FDH- 95% AWC treatment produced the highest average crop yield of 0.88 kg plant−1, compared to the ODH (0.32 kg plant−1) and control treatments (0.40 kg plant−1). The hydrogel and AWC combinations did not significantly (p > 0.05) impact plant height and stem diameter, while these treatment combinations significantly enhanced crop yield, leaf area index and plant biomass (p < 0.05). FDH and ODH produced higher yields and saved 15 % and 20% of irrigation water (225mm), respectively, compared to the control treatment. There was a noticeably higher water use efficiency in the FDH-95 (3.9 kg m−1 plant−1) treatment compared to the ODH-95 (1.46 kg m−1 plant−1) and control (1.5 kg m−1 plant−1) treatments. The results that under FDH and ODH treatments, excess nitrate was stored in the soil vacuoles and was remobilized for uptake by the plant roots. Moreover, the re-swelling ratio of freeze-dried beads (415.62 ± 18.13%) was recognizably higher than that of oven-dried beads (224.16 ± 5.51%), as freeze-dried beads could re-swell 185.4% times more in water than the oven-dried beads. Therefore, this research demonstrates a clean technology whereby wastepaper can be recycled into biodegradable hydrogels to increase crop productivity.