Growth and yield of sorghum under different conservation tillage and water and nutrient management practices in the South Sudan Zone of Burkina faso

A study was conducted in Nadion, located in the South Sudan zone of Burkina Faso to assess the impact of no-till, tied ridging; ripping and conventional tillage combined with soil fertility management options on soil chemical and physical properties and on sorghum growth and yield. The fertility management options were Control, 2.5 Mg ha -1 of compost, 100 kg ha -1 of NPK + 50 kg ha -1 of Urea, mulching (100 % crop residues applied and 2.5 Mg ha -1 of compost + 100 kg ha -1 of NPK + 50 kg ha -1 of Urea. The experiment was factorial, laid out in split-plot and arranged in a randomized complete block design with three replications on a Lixisol with a slope of 1.5%. Soil moisture was monitored weekly. Soil bulk density, total porosity, aeration porosity were assessed. Infiltration measurements were done after harvesting. Soil samples were analysed for pH, organic carbon, total nutrient (N, P, K) and available nitrogen (NO3 --N and NH4 + ). Plant and grain samples were analysed for nutrient uptake and utilization. Mixed model analysis of the results indicated that conventional tillage decreased soil bulk density at the ploughing depth and increased the total porosity and aeration porosity. Soil structural stability index (StI) tended to decrease under ripping, tied ridging and conventional tillage practices after two years. Infiltration rate varied between 0.82 and 1.15 cm h -1 in the order of Ripping > Conventional tillage > Tied ridging > Zero tillage. Field saturated hydraulic conductivity (Ks) varied from moderately rapid (6-8 cm h -1 ) under ripping, through rapid (8 – 12 cm h -1 ) under Conventional, to very rapid (>12 cm h -1 ) under Zero and Tied ridging. All the tillage treatments recorded greater sorptivity than the Zero tillage with the percentage increment being 3, 7 and 10 under Tied ridging, Conventional and Ripping respectively. The pore sizes varied from 6 to 105 µm (0.006 to 0.105 mm) under Tied ridging and Ripping respectively with a trend of iii Tied ridging > Zero tillage > Conventional tillage > Ripping. Infiltration rate the soil amendments was in the order of NPK + Urea > Control > Compost > Mulch > Compost + NPK + Urea. Saturated hydraulic conductivity was moderately rapid under control, rapid under compost and very rapid under mulch, NPK + Urea and compost + NPK +Urea. Sorptivity under the amendments was in a decreasing order of Compost > Control > NPK + Urea > Compost + NPK + Urea > Mulch with values ranging from 0.535 to 0.781 mm S 1/2 for mulch and compost respectively. The hydraulically functioning pores size recorded under the various soil amendments ranged from 0.008 mm to 0.082 mm in an increasing order of Control < Compost < NPK + Urea < Mulch < Compost + NPK + Urea. At the 0-30 cm depth, soil water stock was significantly higher under Zero tillage than the remaining tillage practices from the third to the ninth week. The mean weekly water stock over the 12 week period of measurement at 30-50 cm depth followed a trend of Tied ridging > Conventional tillage > Zero tillage > Ripping with a range between 31.78 and 43.72 mm for Ripping and Tied ridging respectively. The mean cumulative soil moisture stock at 0-50 cm also varied significantly only at the 4 th and 5 th weeks with the Tied ridging recording the highest. Sorghum straw mulch significantly improved soil water stock than the Control at all depths. NPK + Urea application decreased soil pH while the Compost and the Compost + NPK + Urea application led to an increase in the pH. During the peak rainfall period, ammonium - N content decreased under Tied-ridging and Conventional tillage practices while it increased under Ripping and Zero tillage practices. Tied-ridging and Conventional tillage improved sorghum plant P uptake. The application of NPK + urea and its combination with compost also increased nutrient uptake but reduced their utilization compared to the Control. The combined application of Compost and mineral fertilisers improved soil organic iv carbon, total nitrogen, total phosphorus and total potassium content. In 2012, Ripping increased sorghum grain yield by 14% while the Conventional tillage and the Tied-ridging decreased it by 29% and 40% compared to the Zero tillage practice. The application of Compost + NPK + urea, NPK + Urea and Compost led to 74%, 50% and 29% increase respectively in grain yield over the Control. The two - years cumulative effect of Tied-ridging x Compost + NPK + Urea increased sorghum grain yield by 13% and 28% compared respectively with Zero tillage and Conventional tillage with the same fertility management options.

Source: KNUST