**5. Digestate a better stimulant for agricultural production**

Change in the agro-ecological landscape is a serious challenge. This change was observed in humans, society, and the soil ecosystem [25, 26, 35]. This change brought uncertainty to the soil–plant atmospheric system and variation in the environment. This has resulted in continuous depletion of SOM with ease [12, 13]. Similarly, in an agricultural market survey conducted in Europe. It was discovered that after 1990 a negative phenomenon was recorded in agricultural production [12, 30]. The practice of crop rotation was reduced. Increasing demand for staple food brought a cut down in forage crops by 35% [6, 25]. The production of cereal was increased by 54% and rapeseed by 343% [5, 46]. Likewise, a cut down was documented in animal husbandry by 50% [5, 9, 46]. This was identified as a depleting factor for soil organic matter [5, 9, 46]. The use of mineral fertilizer, organic waste, and manure was found useful but digestate was twice richer compare to other forms of manure [3, 15, 30]. Digestate is made of plants with a large amount of N and P. It is a by-product biogas plant that is capable of providing a high yield of spring crop [3, 15, 30]. It is an excellent fertilizer that can enhance the biological properties of the soil. It is widely used in Europe [2, 17, 30]. Digestate average dry matter content ranges between 1.5% and 46%. Digestate is primarily effective at building up the biological quality of the soil [30]. It can efficiently increase the nutrient quality of the topsoil. It plays a significant role in the carbon pool. SOC content initiates positive or neutral ions with the application of digestate [45, 47]. The amount of organic matter applied to determine the SOC content. The higher the digestate, the larger the SOC vice versa [24, 35]. It was reported that larger particles have a positive influence on SOC content than fine particles [30]. The use of animal droppings as the organic compound was significant [12, 40]. Continuous application of digestate creates a better environment for the decomposition of organic matter. It was also recorded that soil with low quality may prevent the decomposition of organic matter [22, 23, 45]. Accurate dosage of fertilizer and accelerated biological processes in the soil enhance productivity [22, 45, 47]. A decrease in pH and soil sorption complex saturation was found to be an attribute of digestate [30]. This may be due to hydrogen and aluminum ion replacement. A significant reduction was recorded in soil acidification with the application of digestate [3, 15, 30]. The agricultural intensive area was typically high in biological activity. This is significant with soil depth [13, 16, 40]. SOC sequestration is high with the regular application of organic manure. It was recorded that a significant amount of 10 t ha−1 of organic manure can increase the SOC stock by 5.5% in 100 years [30, 34, 48]. The use of mineral fertilizer and farmyard manure was also significant to the soil to increasing soil fertility, SOC, and nutrient content [13, 16, 40]. It provides stable nutrients and decreases soil acidity. It was observed that regular application of organic manure provides long-term stable yield and as well improves the quality of the soil [13, 16, 40]. It was found that the use of organic manure and straw is highly valuable to the soil ecosystem [3, 8, 17]. Sufficient application of digestate to the soil can positively influence SOM and SOC content without other manure [15, 30].

**Figure 2.**

*Digestate production and organic carbon sourced from [49].*

Long-term application of digestate maintains SOC content. Postharvest reduces such as straw provide an additional source of organic carbon [4, 24, 30]. A decrease in SOC was recorded in an intensive permanent grassland but SOC and SOM were higher in permanent grassland compare to arable land **Figure 2** [29, 37].
