David B. Mengel

Placement and source effects of phosphate fertilizers on phosphorus availability and reaction products in two reduced-till soils: A greenhouse study

Abstract Crop yields are limited primarily by unavailability of nutrients in agricultural soil. Adoption of reduced-tillage and no-tillage systems leads to stratification of nutrients in surface soil, so management of phosphorus (P) in these systems is a major issue. The objective of this research was to understand the influence of placement (broadcast vs. deep-placed P) and fertilizer source (granular vs. liquid P) on the reaction products of P under greenhouse conditions using soil columns. Phosphorus was added at a rate of 75 kg/ha to two soils: an acid soil from Manhattan, KS, and a slightly acid to neutral soil from Ottawa, KS. At 5 weeks after P application, soil pH, resin-extractable P, and speciation of P in soils were determined at different distances from the point of fertilizer application. Scanning electron microscope with energy-dispersive X-ray analysis and synchrotron-based X-ray absorption near-edge structure spectroscopy were used to understand P speciation. Results for P fertilizer sources and placement with respect to resin-extractable P showed no clear differences between the treatments except for granular broadcast and granular deep-placed treatments in the Ottawa soil. Reaction products formed after application of P in two soils showed some clear differences. The X-ray absorption near-edge structure speciation revealed that Fe-P-like forms dominated in the acidic soil, whereas adsorbed and Fe and Ca-P-like forms dominated in the neutral to slightly acid soil. No clear trends in reaction products were detected with respect to P source or the P placement method. Furthermore, scanning electron microscope with energy-dispersive X-ray analysis of incubated fertilizer granules extracted from soils at 5 weeks showed enrichment of Al, Fe, and Ca in the zones of remaining P in incubated granules, indirectly indicating that these cations enter and or remaining in the granules and begin to react with P before the granules dissolve completely.

Meta-analysis of Winter Wheat Response to Chloride Fertilization in Kansas

Cereal grain yield response to chloride (Cl) fertilization has been reported in most of the Great Plains. The objective of this study was to use meta-analytic methods to summarize and provide quantitative estimates of the effects of soil and fertilizer Cl on wheat (Triticum aestivum L.) response including grain yield and flag leaf Cl tissue level. Meta-analysis evaluated the effect of soil and fertilizer Cl application from different studies on a common scale of effect size. Chloride tissue concentration using the flag leaf correlated well with fertilizer plus soil Cl at a depth of 0–60 cm. However, our analysis indicates possible luxury uptake of Cl in relation to grain yield, with a possible upper limit in plant uptake with soil Cl levels around 68 kg Cl ha–1. Application of Cl fertilizer generated average wheat yield increases of approximately 8%.