Effects of deficit irrigation combined with the use of biochar and compost on the growth, yield and water use efficiency of green pepper

Abstract

Introduction

Agriculture plays a crucial role in fulfilling human needs, but it is also the world's largest consumer of freshwater. This has a significant impact on water resources worldwide, particularly in arid and semi-arid regions. With the growing global population, agricultural production must be increased to meet demand. This has led researchers to explore various methods, including deficit irrigation techniques, soil nutrient enhancement, and water retention agents, to improve crop performance and productivity. Numerous studies have investigated these methods to enhance crop performance and to reduce water consumption. Previous research has also highlighted the potential benefits of biochar application at a 2% level to improve plant performance. This study aimed to evaluate the effects of continuous deficit irrigation (CDI) along with use of compost as a soil nutrient enhancer and biochar as a water retention agent on the performance, growth, and productivity of bell pepper plants. The study examined the effects of these treatments individually and in combination, as well as the combined effects of biochar and sugarcane bagasse compost at 1.5%, 2%, and 2.5% weight levels and their interactions with CDI on water savings and performance improvement of bell pepper plants in a sandy soil.

Materials and Methods

To investigate the research objectives, during 2023, in the research greenhouse of Tarbiat Modares University, a factorial experimental design was implemented in the form of a randomized complete block design with three factors and a total of 48 treatments in four blocks with a total of 192 pots. The first factor includes three levels of irrigation: 100% (D100), 75% (D75), and 65% (D65) of the plant's water needs. The second factor is sugarcane bagasse biochar with four levels: 0% by weight (B0), 1.5% by weight (B1.5), 2% by weight (B2), and 2.5% by weight (B2.5). The third factor is sugarcane bagasse compost with four levels: 0% by weight (C0), 1.5% by weight (C1.5), 2% by weight (C2), and 2.5% by weight (C2.5). In this research, plant growth rate and plant diameter were investigated, and fruit characteristics such as fruit drop, fruit length, fruit flesh thickness, and fruit fresh weight were investigated. In order to check the functional characteristics of the plant, the number of fruits per plant and the total weight of the fruit per plant, as well as the productivity using the ratio of the total weight of the fruit produced per plant to the volume of water used in each pot, were investigated. The watering of bell pepper plants was not like this. During the 3-day watering cycle, the amount of water used in each pot was calculated and added to the pot, and this cycle continued until the end of pepper cultivation.

Results and Discussion

The results showed that the application of biochar and compost at all levels along with full irrigation had a positive and significant effect on the physical characteristics of the fruit (diameter, length, flesh thickness and fresh weight) compared to the control treatment. The lowest value for fruit characteristics was observed in the control group with 65% plant water requirement. The results for the plant characteristics showed that C2B2.5, C2.5B2 and C2.5B2.5 treatments showed a significant difference in plant height compared to the control treatment. C2.5B2 and C2.5B2.5 treatments also showed the greatest increase in stem diameter and had a significant difference compared to other treatments. Also, the results for the number of fruits per plant and yield showed that C2.5B2 treatment had a significant difference compared to other treatments. It caused a 156% increase in plant yield compared to the control treatment. The lowest number of fruits and plant yield was related to the control treatment. In addition, the C2.5B2 treatment achieved an average productivity of 39.3 kg/m3, which was significantly higher than the other treatments, representing a 139% increase over the control. The control treatment had the lowest productivity with an average productivity of 16.43 kg/m3, which was significantly lower than other treatments. The results of mean square variance analysis related to fruit characteristics showed that the triple effect of biochar, compost and deficit irrigation was significant at the level of 1%, but the triple effect of biochar, compost and deficit irrigation was related to plant characteristics and functional characteristics and productivity. The plant was not significant.



Conclusion

The present study demonstrated that the combined application of biochar and compost in bell pepper cultivation offers substantial advantages. This innovative approach not only significantly enhances crop yield but also improves productivity by optimizing water use. Applying 2% biochar and 2.5% compost to bell pepper plants along with continuous irrigation up to 75% of the plant's water requirement can yield promising results for sandy soils. These findings are particularly crucial for arid and semi-arid regions facing water scarcity. In a world facing water shortages, this method can contribute to water conservation and sustainable agricultural development.