Soil
Root zone sand survey
Summary: The objective this study was to determine the range of soil particle sizes found in golf course greens from Southern California and to gain a greater understanding of the nature of Southern California root zone sands.
A particle size distribution measure (PS) was developed to help characterize root zone sands. The PS value provides a single number that describes the range of particle sizes that comprise the root zone sand. A large PS (>1.2) indicates a higher composition of medium sand particles that is desirable. A small PS (<0.6) indicates a higher composition of smaller particles that is undesirable. The PS value was found to be significantly correlated with a number of other soil factors including organic matter content, percolation rate, bulk density, phosphorus, calcium, magnesium, potassium sodium, boron, iron, copper and interestingly, the age of the green. All of the significant correlations with the chemical composition and age of the soil were negative. A negative correlation means a large PS value sand will hold lower levels of nutrients. This relationship is expected and it is well known that higher sand content soils hold less nutrients than finer textured soils. The relationship between PS and age of the greens suggests that the greens are constructed using high sand content materials but the root zone degrades into lower quality finer soils after years of use and management. The reduction in PS may result from decomposition of the materials or addition of fine particles during management or from contaminants in irrigation water.
Based upon these results, some preliminary values have been identified to help understand the aging of greens in Southern California. For example, the correlations suggest that the initial percolation rate of materials used to construct Southern California greens is about 20 inches per hour. The initial PS value for new greens is about 1.6. Several other critical age points were also estimated using the PS model. For example, accelerated percolation rates, greater than 12 inches per hour, are desired in the intensively irrigated Southern California region. Based upon the PS and age relationship, a green may drop from the initial 20 inches per hour to 12 inches per hour in about 13 years. The critical low limit of 6 inches per hour percolation rate minimum for a USGA specification green will be reached in 23 years and an unacceptable percolation rate of 2 inches per hour will be attained in 30 years. These values suggest that after about 13 years of use, the root zone sand will no longer percolate adequately to satisfy the needs of golf play in Southern California.
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Principal investigator: Larry Stowell, Ph.D.
Cooperators: Raymond Davies, Virginia Country Club Jim Duffin, Los Amigos Golf Course John Martinez, Arrowhead Country Club Daniel McIntyre, Antelope Valley Country Club Don Parsons, Old Ranch Country Club Mark Phillips, Laguna Hills Country Club Steve Sinclair, Woodland Hills Country Club Reed Yenny Mesa Verde Country Club David Zahrte, Santa Ana Country Club
Sponsors: Above superintendents and PACE Consulting
Efficacy of Microbes in Soil Salinity Reduction
Summary: A simple experiment was initiated to determine the effectiveness of three strains of bacteria claimed to be salt accumulating microorganisms. Some microorganisms are known to accumulate salts from the environment. These organisms might be used to reduce the salinity of soils provided the organisms are capable of accumulating and sequestering the salts effectively. The results described below indicate that the microorganisms evaluated in this study did not reduce soil salinity.
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Principal Investigator: Larry Stowell, Ph.D.
Cooperator: Don Parsons, Old Ranch Country Club
Sponsors: Old Ranch Country Club and PACE Consulting
Soil Compaction: A Case Study at Candlewood Country Club
Summary: One method of measuring soil compaction, or strength, entails recording the pressure needed to force a rod (cone tip penetrometer) into a soil. If the soil provides resistance of more than 300-400 psi, plant roots have difficulty or are unable to penetrate the soil. For this reason, plant roots are frequently found only in the top 2 3” of soil, where compaction is usually less than 300 psi. In this study, readings taken inside the sand-filled vertidrain holes, one day after vertidrain treatment showed that the vertidrain reduced compaction at depths of 3 - 5” from about 500 psi to less than 400 psi (Figure 1). Five weeks later, we went back to evaluate compaction again, but it was difficult to identify vertidrain holes. For this reason, the readings we obtained (Figure 2) were probably taken from areas between holes. As expected, readings remained unchanged at 500 psi at depths of 3 - 5”. It is likely, however, that the compaction level in the vertidrain holes remained below 400 psi. The common observation of deep roots in vertidrain holes supports this hypothesis. An additional advantage of vertidraining may be improved water infiltration. Even though compaction was not relieved in general throughout the green, the greens take water well in the summer indicating that water infiltration is one of the greatest benefits of this method.
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Principal Investigator: Larry Stowell, Ph.D., CPAg
Cooperator: Mike Caranci, Candlewood Country Club
Sponsor: PACE Turfgrass Research Institute
