Residual Effects of Phosphorus Sources in Grain Amaranth Production

Abstract

2 Productivity of grain amaranth can be improved at a reduced cost through combined use of low-cost rock phosphate (RP) phosphorus sources as well as selection of amaranth varieties with high phosphorus (P) use efficiencies. Rock phosphate sources are known to exhibit differences with respect to grain yield, disease tolerance and P use efficiency (PUE) in amaranth varieties. However, very little is known about their residual release of P. It is probable that the differential performances exhibited by the RPs might be a function of their P residual properties after cropping. Based on these premises this study was carried out to evaluate the residual effects of P sources under continuous croppings for grain amaranth production. The study was a factorial experiment with four replications. Four P sources: single super phosphate -SSP, ogun rock phosphate -ORP, sokoto rock phosphate -SRP, and control; three amaranth varieties: NH84/493, NH84/445 and NH84/452 were factorially combined with two soil types: Kandiudult and Haplustalf. In order to monitor the residual effects of the P sources the experimental plots were cropped consecutively three times. Results from the study revealed that sandy loam Haplustalf was better than the clayey Kandiudult soil in improving grain amaranth yield under continuous cropping system. Grain yield and relative agronomic efficiency (RAE) decreased with continuous cropping for SSP but increased with continuous cropping for ORP and SRP till second cropping, thereafter there was a decrease. Averaged over the three continuous consecutive croppings, SRP and ORP were 68.9% and 73.5% as effective as SSP in increasing grain yield respectively. It was concluded therefore that ORP and Haplustalf soil are best options for grain amaranth production under continuous cropping system.

Phosphorus distribution and availability in untreated and mechanically separated biogas digestates

“…We assume that in our experiment the amaranth roots released organic acids to mobilize P resources in soil to cover the high P demand of this crop. Outstandingly high P uptakes by amaranth were also found in other studies (Ojo et al, 2010;Brandt et al, 2011;Bachmann et al, 2011). Lower pH values after amaranth cultivation were probably also the reason for the decrease in enzyme activities.…”

Management Options for an Efficient Utilization of Phosphorus in Agroecosystems

“…In a pot experiment incorporation of phacelia plants increased the P uptake of the following maize (Zea mays) more than an application of Triple-Super P or cattle manure (Eichler 2004). Outstanding high P uptakes were found for amaranth (Amaranthus cruentus) (Bachmann et al 2011;Brandt et al 2011;Ojo et al 2010), which was related to a considerable decrease of soil pH values-mainly due to the excretion of organic acids (Li et al 2006). The prediction of Prelease from plant tissue is difficult, since the decomposition of the green manure material is a complex process depending on P content in soil, amount and N/P ratio of the green material, P mineralization rates, and P cycling (Oberson and Joner 2005).…”