THE COMBINED EFFECT OF THE TILLAGE DEPTH AND COMPOST APPLICATION ON CALCAREOUS SOIL AGGREGATES AND THE YIELD OF INTERCROPPED FABA BEAN WITH WHEAT

Abstract

Calcareous soils crusting and low organic matter (OM) content are key problems restrict their management and productivity. The aim of this study is to assess the role of tillage at different depths along with the compost application for improving some characteristics of the calcareous soil as well as the yield, and its components of the intercropped faba bean with wheat (1:1 ratio). A field experiment was carried out at the Nubaryia Agricultural Experimental Station through the two successive winter seasons (2019/2020) and (2020/2021) in a split-plot design with three replicates. The main factor (F1) was the plough depth treatments: Chisel plough (20 cm depth) and subsoiler (40 cm depth) one time and twice. The sub-factor (F2) was the applied compost (C1= 5.95 and C2= 11.9 tons ha-1). A control without additions was involved. The wheat and fababean were sown in a 1:1 intercropping ratio mixed with the surface layers by hatchat under a surface irrigation system and the recommended agronomic practices were followed. The tillage treatments combined with increasing the rate of the applied compost have increased the total stable aggregates (TSA), the aggregation index and aggregation degree in the surface and subsurface soil layers (0 – 20 cm, 20 – 40 cm) as well as the saturated hydraulic conductivity (Ks) for both seasons. The water stable aggregates (WSA) distribution revealed that the 8-2 cm aggregates are the abundant size especially in the surface soil layers. The 40 cm depth subsoiler twice treatment combined with the compost rate C2 resulted in the maximum OM for both seasons. The relative maximum OM increase (%) compared to the corresponding control was by 32.3 and 26.7% in the 0 – 20 cm soil layer and by 64.9 snd 60.0% in the 20 – 40 cm soil layer. For the compost rate C2, the most significant relative increase in the wheat grains yield (kg ha-1) was by 74.8% with the plowing two times at 40 cm depth, while for the faba bean seeds yield (kg ha-1) it increased by 145.5% with the 20 cm depth plowing. The studied treatments were effective for improving the calcareous soil properties and productivity.