Agronomic and Environmental Effects of Phosphorus Fertilizer Application Methods
Date
2017-11-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-1080-0143
Type
Thesis
Degree Level
Masters
Abstract
As farm size increases on the Canadian prairies, improving operational efficiency is important for growers. While seed row placement is generally considered the most effective phosphorus (P) placement method for small grains, there are few recent studies comparing agronomic effectiveness of different P fertilizer placement strategies on the prairies in modern no-till cropping systems and environmental considerations must be made in tandem as snowmelt runoff is an important exporter of P in the prairies. The objective of this research was to evaluate the effect of application strategy of monoammonium phosphate fertilizer (MAP) on crop response and P export in a simulated snowmelt runoff and leachate water over two consecutive years of application. The field study was conducted on a typical no-till field with good inherent P fertility located in the Brown soil zone in south-central Saskatchewan near Central Butte. Three in-soil MAP placement treatments (seed placed, deep banded, and broadcast with incorporation) at 20 kg P2O5 ha-1 and three broadcast (20, 40, and 80 kg P2O5 ha-1) treatments were applied each spring along with a control without P fertilizer in an RCBD set up on two sites in the field. Wheat (Triticum aestivum var. Waskada) was seeded in 2015 and canola (Brassica napus var. LL 250) was seeded in 2016. Treatment was not significant in 2015. In 2016, treatment was significant and uptake of P by canola was significantly higher in the 80 kg P2O5 ha-1 broadcast treatment than in other treatments. In the fall of 2016 after harvest, soil monoliths were collected and used to assess vertical and horizontal distribution patterns of soil available P in the surface soil profile. Mapping of residual P indicated zones of depletion below 5-cm in the in-soil P placement treatments, likely due to stimulated root growth, while the broadcast treatment revealed minor surface loading of P. Only the broadcast application at the high rate (80 kg P2O5 ha-1) showed enhanced export in the simulated snowmelt runoff and leachate, and a higher proportion of the P in snowmelt runoff was in the dissolved reactive fraction in this treatment. Assessment of P forms in the runoff using NMR spectroscopy suggested that higher application rates may also be associated with increased microbial activity and production of organic P forms in the soil. Due to high inherent fertility, lower rates of P would be advisable in these soils as crop response to fertilization was limited and high rates of broadcast MAP substantially increased P export in water.
Description
Keywords
phosphorus, eutrophication, nuclear magnetic resonance, nmr, fertilizer
Citation
Degree
Master of Science (M.Sc.)
Department
Soil Science
Program
Soil Science