Effect of clay amendments on nitrogen leaching and forms in a sandy soil

Nitrogen (N) leaching in sandy soil decreases fertiliser use efficiency and may depress plant production. Application of high cation exchange capacity (CEC) materials (e.g. high activity clay minerals) is hypothesized to reduce N leaching and increase plant N uptake in sandy soils. However, the mechanism of leaching in sands with clay amendment is not understood. A column experiment was conducted to determine N leaching and N concentration in soil solution in a sandy soil (1.4 % clay) with three soil amendments (nil, clay soil and bentonite clay) and three fertiliser rates (0, 28 N 17 P 22 K kg/ha and 56 N 34 P 44 K kg/ha). Soil amendments were applied at the rate of 50 Mg/ha. The soil columns were leached with de-ionised water equivalent to 50 mm rainfall every 4 days. Concentrations of soil solution extracted by Rhizon samplers indicated that NH4 leaching was decreased 38-43 % by bentonite addition but little of the soil solution N was in NO3 form and bentonite had no effect on mobility of this form of N. The application of bentonite was able to hold NH4 in soil solution of top soil. Leaching of NH4 was delayed to 15 day after fertiliser application in bentonite-amended sand

Growth and yield responses in maize to split and delayed fertilizer applications on sandy soils under high rainfall regimes

The yield of maize (Zea mays L.) on sandy soils with high rainfall regimes is generally low due to poor nutrient use efficiency. Split and delayed basal fertilizer applications are possible strategies to improve the crop yield and reduce nutrient loss through leaching in sandy soils, but their effectiveness under high rainfall regimes to produce a maize growth response needs further investigation. The aim of the study was to determine the effect of fertilizer application methods on the growth, yield and agronomic characteristics of maize on a sandy soil with approximately 1,350 mm of rainfall during crop growth. Field experiments were conducted on Oxic Paleustults (Korat series) with a low cation exchange capacity (CEC) of 2–4 cmol kg–1. Three to four split applications of the fertilizer increased the grain yield from 2.7 to 3.3–4.5 Mg ha–1. There was a greater crop growth rate (CGR) and relative growth rate (RGR) with the split applications of fertilizer during 30–60 d after emergence (DAE). The highest agronomic efficiency (AE) resulted from a three-split application. However, application of fertilizer later than 45 DAE had only a low effective rate. Delaying the basal fertilizer application to 7–15 DAE increased the grain yield to 3.5–3.7 Mg ha–1, whereas a pre–planting application produced a yield of 2.7 Mg ha–1. Delaying the basal fertilizer application to 7–15 DAE improved the CGR, RGR and AE. These results indicated that fertilizer applications to minimize nutrient loss increased the growth and nutrient use efficiency of maize on sandy soil in a high rainfall regime

Fertiliser strategies for improved nutrient use efficiency on sandy soils in high rainfall regimes

Fertiliser application strategies for maize (Zeamays L.) production on sandy soils under high rainfall regimes need to be carefully designed to minimise nutrient losses through leaching and maximise crop yield. Experiments were conducted to determine N, P, and K leaching in sandy soils with 3-6% clay in surface layers under maize production, and the effectiveness of different N, P, and K fertiliser timing and splitting strategies on leaching of N, P, and K and on maize yield. In a column experiment on an Oxic Paleustult (Korat series) with 3% clay, leaching of N, P, and K from fertiliser (114N-17P-22K in kg ha-1) was significant under simulated rainfall, but decreased to negligible levels with 3-5 split applications of fertiliser. Maize N and K uptake increased with 3-5 split applications, but not P uptake. Despite continued intense rainfall and further fertilizer additions, leaching was not recorded after day 30, and this was attributed to the effect of plant water uptake on reducing deep drainage. Split applications of fertilizer maintained NP and K in the 0-30 cm layer during 30-60 days when maize nutrient demand was likely to be at its highest, while in the recommended fertilizer regime NPK in the surface layers declined after 30 days. In a field experiment on an Oxic Paleustult (Korat series) with 6% clay, 3-4 splits of fertiliser increased N and K uptake and increased maize yields from 3.3 to 4.5 Mg ha-1. Postponing basal fertiliser application from pre-planting to 7-15 days after emergence increased uptake of N, P, and K and grain yield emphasising the greater risk of nutrient losses from fertiliser applied at planting than later. Strategies designed to reduce the amount of nutrients applied as fertiliser at planting, such as split application and postponing basal application can decrease the risk of leaching of N, P, and K from fertiliser and improve nutrient use efficiency, and grain yield of maize on sandy soils under high growing season rainfall regimes