Performance evaluation of cone penetrometer device for measuring the subsoil compaction in mulched plots

Soil exhibits layers of extreme compaction from both natural causes and wheel traffic. These compaction layers impede root growth, thereby reducing the plants capacity to obtain water during drought. Subsoil tillage is a remedy for adverse soil compaction that results in improved conditions for crop growth. Mechanical disturbance of subsoil increases water holding capacity and reduces impedance to root penetration. Vertical mulching is a technique that can be used to partially alleviate soil compaction within the critical root zones of deep rooted crops. A study was conducted by placing raw and composted coir pith using a two row subsoil coir pith mulching machine in three different soil depths (250, 350, and 450 mm) at the three application rates of 15 t/ha, 20 t/ha, and 25 t/ha and the effect of soil strength was investigated. The experiment was conducted for a rainfed cotton crop. The soil strength profile was recorded in all the treatments. The cone penetrometer resistance was measured for each increment of 10 mm and recorded manually from a digital force indicator during maturity stages of crop in all the treatment plots. The cone penetrometer resistance was measured directly on the row and the cone index was computed. Deep placement of mulch reduced the soil strength as compared to shallow placement. The lower soil strength (0.5 kPa to 0.8 kPa) in the loosened and mulched zone provided an impedance free zone for the root to proliferate. The rapid increase in cone index values at depths immediately below the respective depth of placement (250, 350 and 450 mm) of raw and composted coir pith mulch indicated that the existence of undisturbed soil profile below the mulched zone which could be potential limiting factor for root development.