Soil physical properties in relation to maize (Zea mays) yield after tillage and application of organic and inorganic fertilisers in Abeokuta, southwestern Nigeria

Abstract

Moderation of soil disturbance following tillage operations using external inputs, particularly organic manures, is becoming an important aspect of soil tillage management. This study examined the effects of tillage, poultry manure (PM) and NPK fertiliser on soil physical properties and their relationship with maize yield. The experiment was a split-split-plot design with three replications. Tillage (zero tillage (ZT), minimum tillage (MT) and conventional tillage (CT)) was the main plot, the subplot contained four NPK fertiliser treatments (0, 90, 120 and 150kg N ha–1), and the sub-subplots comprised three PM treatments (0, 10 and 20 Mg ha–1). The soil texture was gravelly loamy sand. Soil bulk density (BD), total porosity (Pt), clay dispersion ratio (CDR) and saturated hydraulic conductivity (Ks) were evaluated. Samples for BD and Ks were collected from the soil surface using stainless cylindrical soil core (5cm in diameter and 5cm in height), whereas samples for CDR determination were collected at 0–20cm soil depth. Compared with the ZT, significantly lower BD was obtained under CT plots at 4 weeks after planting (WAP), which increased at 12 WAP possibly due to slaking and collapse of soil particles by raindrops. Application of PM resulted in significantly lower BD than the unmanured plots. There was a significant interaction effect among tillage, PM and NPK fertiliser on soil physical properties. In plots treated with combined 20 Mg ha–1 PM (PM20) and 150kg N ha–1, the soil Pt of 55.6% and 57.2% obtained under CT and MT respectively at the end of the second year were significantly higher than those of the control plots (48.5% (CT) and 47.5% (MT)). In general, combined application of NPK and PM did not result in significant differences in CDR and Ks under MT and CT but the higher rate of PM (PM20) and NPK fertiliser under ZT significantly raised the CDR and reduced Ks by 20–43% in 2008 and 23–45% in 2009 relative to the unmanured plots. This implies disaggregation (higher CDR), which possibly resulted in creation of water-repellent properties causing lower Ks. Although Ks and CDR showed no significant relation with grain yield, BD was significantly related with maize grain yield with MT tending to produce ~23% and 20% higher maize grain yield than ZT and CT respectively under a typical arable surface soil BD. Therefore, integrated use of PM and NPK fertiliser is beneficial to soil physical qualities, especially under tillage management, but high quantities of PM should be avoided under ZT soil.