Soil Macronutrient Responses in Diverse Landscapes of Southern Tallgrass to Two Stocking Methods

Brian K Northup,Kenneth E Turner,Patrick J Starks

doi:10.3390/agronomy9060329

Brian K Northup, Kenneth E Turner + Show 1 more

Open Access

https://doi.org/10.3390/agronomy9060329

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Abstract

Macronutrient (N, P, S, K, Ca, and Mg) availability and distribution in soils of grassland ecosystems are affected by diverse factors, including landscape position, climate, and forms of management. This study examined flux in plant-available macronutrients in production-scale (60 to 80 ha) paddocks of southern tallgrass prairie of central Oklahoma, United States, managed (2009–15) under two contrasting stocking methods (continuous yearlong; rotational stocking among 10 sub-paddocks). Macronutrient availability within the 0–7.5 cm and 7.5–15 cm soil depths were determined with sets of anion-cation exchange membrane probes at 16 locations within paddocks, oriented along transects from water sources to far corners. No clear overall effect related to stocking method was recorded for all macronutrient distributions. The only significant stocking method × location interaction occurred for K (p = 0.01). All other macronutrients displayed significant (p < 0.08) location effects that were common across stocking methods. Effects relatable to stocking method occurred in interactions with soil depth or time of year (p < 0.10), but responses of macronutrient flux to stocking method in these interactions varied. Higher flux occurred in available S, Ca, and Mg in proximity (<24 m) to water sources, which may be related to grazing, but local features of the landscape may also have been involved. More attention to landscape features included within paddocks, and standardized organization of water and other features within paddocks, would improve the potential to define grazing effects on macronutrient distribution.

Highlights

Macronutrients are present in a range of forms within soils of grasslands, and are related to the nature of underlying parent materials [1]
Percentages of different particle fractions of soils in paddocks assigned to continuous stocking were less consistent than in sub-paddocks assigned to rotational stocking, which was likely due to the greater number of soils encountered within these larger units [25]
Responses noted during this study did not provide clear definitions of the impact of stocking methods on amounts and distributions of flux in most plant-available macronutrients within paddocks

Summary

Introduction

Macronutrients are present in a range of forms within soils of grasslands, and are related to the nature of underlying parent materials [1]. Macronutrient availability and distributions are affected by type and productivity of plant communities, position within landscape, and climate, and varies with time [1,2,3]. Livestock grazing has been considered an important component of altering availability of macronutrients within grassland ecosystems. Redistribute macronutrients within consumed biomass through removal by grazing, movement of nutrients off-paddock in body weight, and recycling through excreta that is returned to the landscape [3,4,5,6]. Re-distribution of macronutrients in excreta tends to be non-uniform, and can result in high concentrations within localized areas of paddocks [7,8]. Increased amounts of labile N, P, K, and S were reported in areas adjacent to watering facilities, corners, and other paddock structures [6,9,10]

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