Effect of Tillage Systems, Plant Residue Management and Potassium Fertilizer Application on Yield and some Physiological Characteristics of Roselle (Hibiscus sabdariffa L.)

Crop residue management is one of the main pillars of production in agriculture and in the long run plays an important role in increasing or decreasing crop yields. Adequate amount of potassium sulfate fertilizer in the soil modulates the osmotic pressure in the soil. in this way, the plant's ability to withstand drought increases. Due to the fact that sour tea is one of the most important medicinal plants in Sistan, so it needs more study and research. Therefore, this experiment was conducted to investigate the effect of tillage systems combined with crop residue management and application of potassium fertilizer on yield and some physiological characteristics of sour tea in Sistan climate.

In order to investigate the effect of tillage systems with crop residue management and application of potassium fertilizer on yield and some physiological characteristics of sour tea, an experiment was conducted in the research farm of zabol university agricultural research institute in 2018-2019 as a split plot-factorial in the form of complete block design. randomization was performed in three replications. experimental factors including tillage systems at three levels without tillage, reduction tillage (disc) and conventional tillage (plow + disc) as the main factor and the combination of plant residues at three levels (zero, 30 and 60%) with potassium sulfate fertilizer at three levels (no fertilizer, 75 and 150 kg  ha-1) were considered as secondary factors. measurements were: economic yield, biological yield, harvest index, chlorophyll a, b and carotenoids, anthocyanins, flavonoids and protein.  statistical analysis of data was done with SAS software version 9.1 and mean comparison with duncan test was conducted at 5%.

The results showed that the use of tillage systems and their interaction on the studied characteristics were significant, However, plant residue treatments and their interaction on the studied characteristics except harvest index and anthocyanin were significant, Potassium sulfate treatment and its interaction on the studied properties except harvest index and flavonoids were significant. The highest economic yield of sour tea was equal to 3221.7 kg  ha-1 in the reduced tillage system with 60% of crop residues and 150 kg  ha-1 of potassium sulfate and The highest amount of sepal anthocyanin was obtained from conventional tillage treatment and combined use of 30% residues and 75 kg  ha-1 of potassium sulfate and Conventional tillage and combined use of 30% residues and 75 kg  ha-1 of potassium sulfate increased chlorophyll a, b and carotenoids. Also, non-tillage and conventional tillage treatments increased the amount of flavonoids and protein at the branches. The results of comparing the means of interaction of tillage systems with crop residue management and application of potassium sulfate show that the highest increase in chlorophyll a and carotenoid content of conventional tillage is + 30% of crop residues and 75 kg  ha-1 of potassium sulfate And the highest increase in chlorophyll b was the simultaneous use of conventional tillage + 60% of crop residues and 150 kg  ha-1 of potassium sulfate. the highest amount of protein was related to conventional tillage treatment with zero percent of crop residues and potassium sulfate, the results of comparing the means on the interaction of the treatments showed that the simultaneous application of no-till treatment with zero percent of crop residues and potassium had the best effect on the amount of flavonoids.

The results indicate that the effect of tillage systems combined with crop residue management and application of potassium sulfate in increasing quantitative and qualitative characteristics has had the best results. Under conservation tillage, by reducing tillage operations and maintaining a sufficient amount of plant residues in the soil surface, while improving soil structure and increasing water efficiency and nutrient efficiency, that increased quantitative and qualitative characteristics. Despite the dry climate in the country and the limitations and shortages of water and reducing soil fertility on the one hand and increasing environmental pollution on the other hand, the need to use conservation agricultural systems to maintain yield and stability and ultimately stability and balance of environmental factors is necessary it seems.