Organic matter accumulation beneath maintained turfgrass systems

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Title: Organic matter accumulation beneath maintained turfgrass systems
Author: Goodman, Harold David
Advisors: Tom Rufty, Committee Chair
Lane Tredway, Committee Member
Danesha Seth-Carley, Committee Member
Fred Yelverton , Committee Member
Abstract: The first objective focused on excessive organic matter (OM) accumulation in creeping bentgrass (Agrostis stolonifera L.) putting greens, which is one of the more important problems in golf course management. Detrimental effects of OM accumulation are particularly acute in the transition zone in the southeastern U.S. In this study, temporal and spatial aspects of OM accumulation were investigated. Root zone samples were collected from 49 golf course greens of different ages. The analyses indicated that OM accumulated very rapidly in the top 2.54 cm, typically exceeding critical levels of 40 g kg-1 within five years. Accumulation over time was best described by a hyperbolic curve, with rates declining to minimal levels within 15 to 20 years. Accumulation at a depth of 2.54 to 7.68 cm was much slower and linear over time, and critical levels were not reached even after 20 years. In field studies on bentgrass plots exposed to different nitrogen treatments, higher nitrogen fertilization led to more rapid OM accumulation, especially near the soil surface. Hyperbolic OM accumulation suggests that the relationship between below-ground bentgrass growth and soil microbial activity changes as greens age, although no mechanistic explanation is available. Rapid accumulation in early years after establishment indicates that it may be unrealistic to expect that OM accumulation can be controlled entirely, but it is clearly essential to intensively manage the system and maintain gas exchange into the rhizosphere throughout the life of a bentgrass putting green. Correct sampling for organic matter levels should be focused near the top of the soil profile. In the second study we examine the extent that C can be accumulated in soil beneath bermudagrass (Cynodon spp.) turfgrass systems. Since substantial evidence indicates that increases in world temperatures are being driven by accumulation of ‘greenhouse’ gases in the earth’s atmosphere, the most important of which is carbon dioxide (CO2), the need to limit or reduce CO2 emissions of has become the most important. It has also been proposed that release of CO2 could be offset by carbon (C) sequestration in long-term storage pools. Recent literature suggests this might be the case, but only one data set has been published and it was from work done in Colorado. For this study, samples were taken from fairways on 59 golf courses of varying ages North and South Carolina. The samples were analyzed using ashing and direct analyzer methods. Direct analysis Accumulation over the first 20 years is about 17.5 Mg ha-1 or 780 lbs per acre in clay soils and about 31.0 Mg ha-1 or 1,400 lbs ac-1 in sandy soils. The potential C sequestration beneath turfgrasses in the Southeast raises the possibility of substantial carbon credits for the turfgrass industry in this region. Lastly, in a series of hydroponic experiments we study how four bentgrass cultivars respond to nitrogen (N) fertility. These experiments clearly show that there is a ‘range’ in N fertilization where shoot growth responds with minimal effects on root growth. It is not possible to relate exact concentrations in solution with fertilization rates in the field, but it is logical to think the target ‘range’, which was about 0.6 mM in our treatments, is similar to that being used with the frequent applications or ‘spoon feeding’ in the field. If fertilization is kept within a ‘target window’ like that identified in these experiments, the possibility for negative environmental leaching effects is minimized.
Date: 2009-12-03
Degree: MS
Discipline: Crop Science

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