Investigating the effect of controlled tillage at black cumin (Nigella sativa) planting on energy consumption, physical properties and soil protection (case study: sloping lands of Hezarjarib region, Behshahr)

Recently, conservation tillage (controlled) as a soil stabilization factor has been given much attention so that the soil is less disturbed and at least 30% of plant cover to remain on the soil surface. This greatly helps to maintain soil structure and moisture, especially in sloping fields. The fields of the Hezarjarib Behshahr region are steep, and due to the cold and dry climate and the wind blowing most of the year, it is very important to stabilize and maintain the soil moisture and structure and prevent it from being washed away by the wind. On the other hand, the sloping lands of this region are under dryland cultivation of wheat and barley, which have little income for farmers and require alternative crops. In this way, Black cumin (Nigella sativa) plant is a valuable substitute for them. Therefore, the purpose of this study was to investigate the effect of controlled tillage to cultivate black cumin plants on energy consumption, physical properties and soil protection, as well as plant performance in the sloping lands of Hezarjarib Behshahr region.

The investigated parameters included the required draft force by tillage tool, tractor fuel consumption, and changes in the degree of soil fragmentation and permeability before and after tillage. The input variables included root cutter supplement in two levels (without and with root cutter), tillage depth in two levels (35 and 28 cm for chisel) and forward speed in two levels (low gears 1 and 2). Considering 3 replications for each treatment, a total of 24 experimental plots with 2m width and 40m length were created with the random complete block design (RCBD) method and perpendicular to the slope. Regarding the yield and yield components of black cumin, after harvest, biological yield parameters, root weight, root length, root diameter, the width of root distribution, number of follicles per plant, number of seeds per follicle, thousand seed weight, plant height, stem diameter and performance were measured per unit area.

The results showed that the effect of the input variables was significant only on the required draft force by tillage tool and the tractor fuel consumption, in addition to the biological yield and the yield per unit area of black cumin. The use of a root cutter increased the required draft force by tillage tool and tractor fuel consumption, while harmed soil permeability and crushing, seed weight, biological yield and yield per unit area of black cumin. The use of higher forward speed leads to an increase in draft force and fuel consumption, and the absence of root cutter, leads to a decrease in soil permeability and fragmentation, biological performance and yield per unit area of the black cumin at a greater depth of tillage, while at a lower depth, no significant (5%) difference can be seen between the two speeds. Increasing the depth of tillage up to the range of vertical root growth due to the negative draft of the tillage tool has reduced the draft force and fuel consumption and had a positive effect on soil permeability and crushing plus crop yield.

The best-researched treatment was the used triple action tillage tool, without root cutter supplement, greater ploughing depth and forwarding with low gear 1. In this way, it will be possible to save 25% in fuel consumption due to the negative draft of the rotary plough, increase the depth of the plough and reduce the required draft force by 25%, increase the biological yield (straw) by 25% and increase the yield by 45%.