Impact of Cover Crops on Phosphorus Biochemical Cycling and Dynamics in Texas Agricultural Soils

Phosphorus (P) is a critical yet often limiting nutrient in agricultural systems. This thesis investigates how different soil management practices and preservation methods influence phosphorus dynamics, focusing on phosphatase activity and phosphorus availability in Texas soils. The research is divided into two major studies. The first examines how soil preservation techniques, including air-drying and freezing, affect measurements of phosphatase activity, an enzyme central to phosphorus cycling. To address the challenges of delayed sample processing, statistical models were developed to estimate phosphatase activity in preserved soils equivalent to that in fresh samples. These models offer a practical solution for maintaining accuracy in non-ideal field or lab conditions. The second study evaluates the effect of buckwheat (Fagopyrum esculentum) cover cropping on phosphorus uptake in wheat (Triticum aestivum) across three Texas soil types, Weswood (WSW), Ships (SHP), and Yahola (YHL), and three wheat cultivars (TAM 107, TAM 110, TAM 304). The study also assessed phosphorus fractionation and enzymatic activity under cover crop (CC) and fallow (F) treatments. General linear models (GLMs) were used to assess how treatment, variety, and soil type affected phosphorus pools across crop development stages, revealing significant treatment x variety interactions in select pools. Buckwheat enhanced phosphatase activity and altered the distribution of labile and moderately labile phosphorus pools. Residual Resin P was generally higher in fallow plots, suggesting significant P uptake by buckwheat. SHP soil, with high calcium content, showed the greatest P accumulation in buckwheat biomass, confirming buckwheat's ability to access calcium-bound phosphorus. Wheat grown after buckwheat generally had higher phosphorus concentration in both straw and grain, particularly in low-P soils and responsive cultivars. In contrast, wheat in fallow plots tended to grow taller and produce more biomass, with TAM 107 performing best, likely due to its adaptability to low-input conditions. Overall, these findings highlight the complex interplay between soil type, management, and cultivar, and underscore the potential of buckwheat cover cropping and predictive modeling to support sustainable phosphorus use and long-term soil fertility.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Soil Science

Grantor

Texas A&M University

Year dc:date.issued

2025

Author dc:creator

• Joharzadeh, Leila 1996-

Advisor dc:contributor.advisor

• Mowrer, Jake

Committee members dc:contributor.committeemember

• Terry J. Gentry
• Joseph Edwards

• Agriculture, Agronomy
• Agriculture, Soil Science
• Environmental Sciences

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/1969.1/1597990

OAI record oai:identifier

https://oaktrust.library.tamu.edu/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aoaktrust.library.tamu.edu%3A1969.1%2F1597990