Growing Carrots crop nutrition advice

What soil type, pH and climate do carrots prefer?

• Soil Type: Carrots thrive in deep, loose loamy soils that facilitate optimal root development. They are adaptable to various soil types, including sandy soils, provided the top 30 inches are uniform and free from obstructions. In some regions, such as Wisconsin, muck soils are prevalent. However, overly heavy soils can lead to deformed roots. Muck soils or loose, friable sandy loam soils are preferred, but carrots can also be successfully grown on heavier soils under irrigated conditions. Good drainage is essential, as carrots do not perform well in waterlogged soils.
• pH Levels: The ideal pH range for carrot growth is between 6.0 and 6.5, although they can tolerate a pH between 5.5 and 7.0. Soil pH below 5.5 may lead to deficiencies in phosphate, molybdenum, and calcium, while levels above 7.5 can cause deficiencies in boron, copper, iron, manganese, phosphate, and zinc. Regular soil testing is crucial for determining the need for lime applications, particularly dolomitic lime if magnesium levels are low.
• Moisture and Irrigation: A consistent and uniform water supply is vital for good color and root formation in carrots. Irrigation should be carefully managed, as carrots should not experience moisture stress at any stage, particularly during germination and root expansion, as this can lead to significant yield reductions. The most serious yield reductions occur when water stress is experienced during the critical early germination phase or during the root expansion phase. Regular irrigation practices, such as drip irrigation or overhead irrigation, can help maintain adequate moisture levels and promote healthy growth.
• Climate: Carrots are cool-season crops that can tolerate warm temperatures early in the growing season. Optimal root color develops when air temperatures range from 60 to 70°F. Carrots grow best in moderate climates, with cooler nights that help maintain soil moisture and prevent excessive evaporation.

Nutrient requirements

Estimated nutrient uptake (kg/t):

Recommendations for the different nutrients depends on soil fertility. 

Carrot is susceptible for high salt concentrations, especially at seedling stage. 

Fertilization methods

Nitrogen: Using a granular fertilizer, apply before seeding approx. 70lbs/N minus any mineral N present in the soil (12 in). The remainder can be split over the crop cycle either on a weekly basis, via fertigation, or 2-3 applications of conventional granular N based products. 

However, in non-fertigated crops, using Controlled Release Fertilizers allows application of the entire amount of N, before seeding, thus avoiding multiple top-dressings. 

Phosphate / Phosphorus: Phosphorus is crucial for root development and overall plant health.  It could be applied entirely at the beginning of crop cycle, before seeding.  Phosphorus should be applied according to soil test results, with a focus on enhancing Total Soluble Solids (TSS) in the roots.  Some recommendations include applying one-third to one-half of the recommended amount banded in the bed width and incorporated before planting. 

Potassium: Potassium plays a significant role in root health and quality.  Knowing that potassium leaches as easily as nitrate, the entire amount that crop needs should be split in 2-3 applications in non-fertigated crop systems or using only once, before seeding, a coated K-based product. It should be applied according to soil test results, with one-third to one-half of the required potassium banded in the planting bed and the remainder applied as sidedressings during the growing season. Target levels for potassium in mature leaves are between 2.0 and 4.0%. In fertigated crops, supplying potassium on weekly basis is strongly recommended. 

Magnesium: Appling magnesium (Mg) sources prior to planting or as a side-dress during early growth stages to ensure sufficient availability for photosynthesis and root development is recommended. Try Polysulphate as an alternative to dolomitic lime. Mg be applied entirely at the beginning of the crop cycle, before seeding. Foliar applications of Mg containing products like Nova FLOW will further improve crop performance and yield by promoting translocation of carbohydrate to the developing root.

Calcium: Could be applied entirely at the beginning of the crop cycle, before seeding. Again, Polysulphate is a gradual release multi-nutrient alternative to gypsum with proven results across multiple crops.  Apply calcium amendments prior to planting to ensure it is available during root development. Aim for a soil pH between 6.0 and 6.5 for optimal calcium availability.

Micronutrients: Nutrients such as boron, copper, manganese, and zinc are crucial for maintaining healthy plant functions. Foliar applications can help correct deficiencies identified through soil tests.

Role of Nutrients in Crop Production

• Nitrogen: Promotes robust vegetative growth and is crucial for enzyme and chlorophyll production.
• Phosphorus: Aids in root development and energy transfer within the plant, contributing to overall yield and quality.
• Potassium: Maintains ionic balance and water status, crucial for nutrient uptake. Adequate potassium is also critical for storage longevity.
• Calcium: Supports cell wall structure, which can impact carrot quality and storage longevity.
• Magnesium: Important for chlorophyll synthesis and enzyme activation, as well as carbohydrate translocation to the root.

Key Fertility Challenges for U.S. Carrot Growers

• Soil Variability: Differences in soil types, texture, and fertility can complicate nutrient management and require tailored fertilization strategies.
• Moisture Stress: Insufficient or inconsistent water supply during critical growth stages can severely affect yield, leading to poor root quality and reduced overall production.
• Nutrient Management: Balancing nutrient applications, particularly nitrogen, is crucial to prevent growth spurts and splitting, which requires careful monitoring and adjustments based on soil tests and plant tissue analysis.
• Pest and Disease Pressure: Carrot crops are susceptible to various pests and diseases that can affect overall plant health and yield. Integrated pest management strategies may be necessary to mitigate these issues.
• Seasonal Constraints: Weather conditions can impact timely fertilizer applications and irrigation practices, making it essential to utilize plant tissue analysis to monitor nutritional status throughout the growing season. This proactive approach can help avoid problems before they become yield-limiting factors.

Sources:

U.S. Environmental Protection Agency. (2004). U.S. carrots crop profile. Retrieved from https://ipmdata.ipmcenters.org/documents/cropprofiles/uscarrots.pdf

Treadwell, D. D., & Hodge, R. (2020). Commercial production and management of carrots. University of Georgia Cooperative Extension. Retrieved from https://extension.uga.edu/publications/detail.html?number=B1175&title=commercial-production-and-management-of-carrots#Soil%20and%20Nutrition

Dufault, R. J., & Tichich, A. (2015). Carrots (E1437). Michigan State University Extension. Retrieved from https://www.canr.msu.edu/uploads/resources/pdfs/carrots_(e1437).pdf