Effects of tillage depth and planting density on photosynthetic characteristics and yield of peanut in coastal saline alkaline land

In order to study the changes of photosynthetic characteristics and yield of peanut in coastal saline-alkaline land under different tillage depths and planting densities, the study was aimed to be conducted in a split-zone experiment in a representative saline-alkaline land of the Yellow River Delta. This experiment is divided into two main time periods: 2023 and 2024, from May to September. The peanut variety “Yuhua 18” was used as the material. The design of the main factor fracture zone was used so as to comprehensively assess peanut growth under different treatment conditions. The main factor split-zone was adopted, as the first major type of treatment area, was set up for three tillage depths treatments of 10 cm, 15 cm and 20 cm, noted D1, D2 and D3 separately. At the same time, the subzones were also divided according to different densities with three planting density treatments of 178,000 plants per hectares, 212,000 plants per hectares, and 261,000 plants per hectares, noted R1, R2 and R3 separately. Under the planting mode of precision sowing of single grains, such partitioning is designed to explore the interactions of different tillage depths and planting densities, which together affect photosynthetic characteristics of peanut leaves at critical reproductive periods such as seedling stage, flowering stage, pod setting stage, and pod filling stage. In addition, including an analysis of yield components at the harvesting stage. The results of the study revealed significant differences in peanut growth status and yield potential under different conditions of treatment. Specifically, under the combination of 212,000 plants per hectares and 20 cm tillage depth, the chlorophyll content and net photosynthetic rate of peanut leaves have performed at the highest level, reached the maximum value at the podding stage. Changes in chlorophyll and photosynthetic capacity during this period helped to increase the overall growth potential of the plant, resulting in an increase in the number of pods per plant and the rate of full pods which were higher than that of the other treatments by percent of 9.52 and percent of 4.58 respectively (averaged for two years). Under the combination of 261,000 plants per hectares planting density and 15 cm tillage depth, the leaf area index of peanut leaves reached the maximum value at the podding stage. This optimized combination of planting density and tillage depth resulted in improved plant population quality and corresponding increases in the rate of kernel and pod yield which were at least higher than that of the other treatments by percent of 5.34 and percent of 2.45 respectively (averaged for two years). Therefore, the above two planting schemes can be used as the preferred choice of high-yielding peanut coupling mode in coastal saline-alkaline land, which are able to make full use of their respective advantages, through scientific management and technical means. By creating the most suitable environmental conditions such as appropriate water, air and heat conditions for peanut growth and development healthily to enhance the efficiency of photosynthesis and promoted the improvement of peanut yield eventually. The results of the study can provide theoretical reference for the development of high-yield peanut cultivation technology in coastal saline-alkaline land, which are of great significance for the exploration and development of saline-alkaline land resources deeply. Meanwhile, it helps to explore more planting options suitable for other cropping patterns of peanut in saline-alkaline land thereby expand the cultivation area of peanut which furthermore, has a decisive impact on guaranteeing a stable supply of food and oil products and of irreplaceable importance for the development and utilization of saline-alkaline land soil resources, so as for guaranteeing the security of national food and oil supply.