Haiying Tao

Optimum Phosphorus (P) fertilization is essential for crop yield and quality, economic return, and the environment. However, agronomic and economic responses to P fertilization are unclear for cabbage grown in the soil and environment in Connecticut. The goal of this study was to quantify agronomic and economic responses to P fertilizer application rates of fall cabbage grown on a P-deficient Woodbridge fine sandy loam in Connecticut. Field experiments were conducted in 2024 and 2025 using five P rates (0, 56, 112, 168, and 224 kg P ₂ O ₅ ha ^-1 ) arranged in a randomized complete block design (RCBD) with four replications. Marketable head yield and head tissue P concentration were analyzed, and their responses to P rates were described using Linear Plateau, Quadratic Plateau, Quadratic, and Mitscherlich models. P applications resulted in significantly greater marketable yields compared with the unfertilized controls in both years, and yield increased significantly up to 168 and 112 kg P ₂ O ₅ ha ^-1 in 2024 and 2025, respectively. Model fit statistics were similar among models but estimated agronomic and economic optimum rates varied widely. The quadratic model ensured the greatest economic net return in both years, with economic optimum rates of 172.8 and 167.9 kg P ₂ O ₅ ha ^-1 in 2024 and 2025, respectively. Head tissue P concentrations increased significantly as P application rates increased up to 168 kg P2O5 ha ^-1 in both years, and the critical concentrations derived by the models ranged from 0.252% to 0.468%. These findings provide preliminary estimates of P fertilizer application rates for optimizing productivity and profitability of cabbage grown in a P-deficient soil representative of a common soil series. Additional experiments are needed to develop P fertilizer recommendations across a broader range of soil series and soil-test P levels in Connecticut.

Introduction: Introducing beneficial soil biota such as arbuscular mycorrhizal fungi (AMF) to agricultural systems may improve plant performance and soil fertility. However, whether bioinocula species composition affects plant growth and soil fertility, and whether fertilizer source influences AMF colonization have not been well characterized. The objectives of this research were to: (1) assess if AMF bioinocula of different species compositions improve raspberry (Rubus idaeus L.) performance and characteristics of soil fertility and (2) evaluate the impact of fertilizer source on AMF colonization.Methods: Five bioinocula with different AMF species compositions and three fertilizer sources were applied to tissue culture raspberry transplants in a randomized complete block design with eight replicates. Plants were grown in a greenhouse for 14 weeks and plant growth, tissue nutrient concentrations, soil fertility, and AMF root colonization were measured.Results: Shoot K and Zn concentrations as well as soil pH and K concentration increased in the Commercial Mix 1 treatment (Glomus, Gigaspora, and Paraglomus AMF species) compared to the non-inoculated control. RFI (raspberry field bioinoculum; uncharacterized AMF and other microbiota) increased soil organic matter (SOM), estimated nitrogen release (ENR), and soil copper (Cu) concentration compared to the non-inoculated control. Furthermore, plants receiving the Mix 1 or RFI treatments, which include more AMF species, had greater AMF root colonization than the remaining treatments. Plants receiving organic fertilizer had significantly greater AMF colonization than conventionally fertilized plants.Conclusion: Taken together, our data indicate that coupling organic fertilizers and bioinocula that include diverse AMF species may enhance raspberry growth and soil fertility.

The time delay in receiving conventional tissue nutrient analysis results caused red raspberry (Rubus idaeus L.) growers to be interested in rapid sap tests to provide real-time results to guide immediate nutrient management practices. However, sap analysis has never been conducted in raspberry. The present work aimed to evaluate the relationship of petiole sap nitrate (NO₃^–), potassium (K⁺), and calcium (Ca²⁺) concentrations measured using compact ion meters and leaf tissue total nitrogen (TN), potassium (K), and calcium (Ca) concentrations measured using conventional tissue nutrient analysis. The relationship of petiole sap NO₃^– and leaf tissue TN concentrations with plant growth and production variables was also explored. Fertilizer treatments of urea were surface applied to raised beds of established “Meeker” floricane red raspberry plots at control, low, medium, and high rates (0, 34, 67, and 101 kg N ha^–1, respectively) in 2019 and 2020. The experiment was arranged in a randomized complete block design with three replications. Whole leaves were collected from representative primocanes in mid- and late- July and August 2019 and 2020 (i.e., four sampling time points per year). At each sampling time point, a subsample of leaves was used for petiole sap analyses of NO₃^–, K⁺, and Ca²⁺ concentrations using compact ion meters, and conventional tissue testing of leaf tissue TN, K, and Ca concentrations, respectively. There were no interactions between N fertilizer rate and year nor between N fertilizer rate and sampling time. No significant differences were found due to N fertilizer rate for petiole sap NO₃^–, K⁺, Ca²⁺ nor leaf tissue TN, K, Ca concentrations. However, significant year and sampling time effects occurred in measured petiole sap and leaf tissue nutrient concentrations. Overall, the correlations between petiole sap NO₃^– and leaf tissue TN, petiole sap Ca²⁺ and leaf tissue Ca, petiole sap K⁺ and leaf tissue K concentrations were non-strong and inconsistent. Future research is warranted as the interpretation of correlations between raspberry petiole sap and leaf tissue nutrient concentrations were inconclusive.

Optimizing nitrogen (N) fertilizer rates maintains good red raspberry (Rubus idaeus L.) production while alleviating environmental risks. Although raspberry growers in Washington are using the caneberry nutrient management guides derived from western Oregon, these guides may not be appropriate for other production regions given the differences in climate, soil type, and crop productivity. However, limited research has been conducted to observe the impact of the N fertilizer rate on floricane red raspberry growth, yield, and fruit quality in Washington. The aim of this study is to evaluate the response of “Meeker” floricane red raspberries grown in northwest Washington, USA, to different N fertilizer rates in order to provide information for future local nutrient management guides. Treatments of urea (46% nitrogen (N)) were surface-applied to raised beds of established ‘Meeker’ raspberry plots at controls, low, medium, and high rates (0, 34, 67, and 101 kg N ha⁻¹, respectively) in 2019 and 2020. The experiment was arranged in a randomized complete block with three replications. Fruit yield and quality, plant growth and leaf tissue nutrient concentrations, and soil characteristics were evaluated. There were no N fertilizer rate treatment effects for the yield, fruit quality, plant growth, leaf tissue nutrient concentrations, and soil characteristics, except for fruit titratable acidity and soil ammonium (NH₄-N) concentrations. The lack of a plant response may be due to nutrients mineralized from soil organic matter (3.81–4.0%) and the utilization of plant nutrient reserves. Based on the results, the soil organic matter level and plant nutrient reserves should be considered when making nutrient management suggestions. Fertilizer costs as well as the potential for environmental pollution from excess fertilizers could be reduced through utilizing these two potential sources of nutrients. Furthermore, longer periods of research is warranted to understand how to adjust N fertilizer rates based on plant and soil characteristics while sustaining yields.