How to Increase Potato Tuber Size and Yield?
Potato tuber size and uniformity are critical for all markets, including fresh potatoes, seed potatoes, and processing crops. Achieving optimal tuber size and yield requires a combination of balanced nutrition and effective crop management practices.
This comprehensive guide explores the key factors influencing potato tuber size and provides practical strategies to enhance growth and yield.
Consider Balanced Nutrition
Balanced nutrition is vital for increasing potato tuber size and yield. A correct balance between macronutrients and micronutrients is essential to obtain the best results possible.
A deficiency of any single nutrient can limit crop yield, as stated by Liebig’s Law of the Minimum, which posits that growth is dictated by the scarcest resource.
Let’s review the roles of essential nutrients and their impact on potato growth.
Macronutrients
Nitrogen:
Nitrogen is crucial for leaf and tuber growth. It is needed during leaf formation and for increasing tuber size by ensuring optimal photosynthate production in the leaves.
- Leaf Canopy and Tuber Bulking: Early nitrogen application helps build the leaf canopy, while later application maintains canopy greenness and maximizes yield. However, excessive early nitrogen can lead to vegetative growth at the expense of tuber formation. Similarly, an oversupply of nitrogen at later stages can result in oversized potatoes and increase the risk of blight infection. In hot, dry climates, additional nitrogen can maintain canopy growth and prolong bulking.
- Nitrogen Form: A balance of ammonium and nitrate is best used at planting. However, too much ammonium nitrogen can reduce root zone pH and promote rhizoctonia. During tuber initiation and bulking, nitrate nitrogen is preferred for its distinct advantages.
Phosphate:
Phosphate is needed in relatively large quantities, particularly during early growth, to encourage rooting and tuber set, and then again during the late season for bulking.
- Foliar Phosphate: Applying foliar phosphate after tuber initiation increases tuber size and yield. However, foliar phosphate should complement soil-applied phosphate, as adequate soil phosphate is necessary for optimal early season growth.
Potassium:
Potassium is particularly important for high yields and maintaining tuber integrity.
- High Yields: Potassium is absorbed in large quantities throughout the growing season. Trials have shown significant yield increases with adequate potassium application. For example, in five trials across three years on potassium-rich volcanic soils, applying 120kg K2O/ha increased average yields by 10t/ha.
Sulphur:
Sulphur is needed for all growth stages and is particularly important in reducing common scab.
Calcium:
Calcium plays a key role in tuber bulking and maintaining stress-free leaf growth.
- Cell Structure: Calcium is a component of cell walls, helping to build a strong structure and ensure cell stability. It is critical during cell division and expansion, making it essential prior to and during the rapid growth phase of tubers.
Magnesium:
Magnesium is needed during tuber bulking, and its deficiency can reduce tuber size and yield.
- Deficiency Impact: Soils with severe magnesium deficiency can reduce yields by up to 15%. Regular applications of magnesium can achieve yield increases of 1 to 10% in trials. Magnesium uptake depends on the balance with other cations, particularly potassium. Foliar applications of magnesium can be effective, especially in dry soil conditions or high potassium environments.
Micronutrients
While much lower amounts of micronutrients are needed, the correct balance is essential for quality crop production.
Boron:
Boron is needed in the greatest quantities among micronutrients to ensure key growth processes proceed unchecked. It is also important in optimizing calcium utilization.
Copper:
While significant quantities of copper are used, deficiencies are rarely seen, with most soils providing adequate long-term supplies.
Manganese and Zinc:
Manganese and zinc are important for yield. Zinc plays a key role in nitrogen assimilation and metabolism and starch formation.
Molybdenum:
Molybdenum can be important in low pH soils.
How to Increase Potato Yield
The two key yield components of potatoes are tuber numbers per unit area and tuber size or weight. Increased yields come from achieving the optimum tuber numbers, maintaining a green leaf canopy, and increasing tuber size and weight.
A balanced crop nutrition program including all macro and micronutrients is essential to help manage these components.
Nutrient Uptake Throughout the Season
Nutrient uptake varies with the growth stage of the crop. There is a large demand for macronutrients during early spring growth. Both potassium and nitrogen are needed throughout vegetative growth, tuber formation, and bulking. Potassium is the element most widely utilized by the potato crop and, together with nitrogen, is required in the highest quantities to achieve high yields. The requirements for phosphate, calcium, and magnesium are less but still significant.
Daily Rate of Macronutrient Uptake in Potatoes
Potassium is particularly important for high yields and maintaining tuber integrity. Nitrogen is important for leaf and tuber growth. Phosphate is needed in relatively large quantities during early growth to encourage rooting and tuber set, and again during the late season for bulking.
Crop Management Practices to Increase Potato Tuber Size
In addition to balanced nutrition, several crop management practices can help increase potato tuber size.
Early Planting:
Planting as early as possible extends the length of the growing season, especially in areas with limited daylight hours.
Planting Physiologically Aged Potatoes:
Planting aged potatoes ensures quick emergence, leading to a longer growing period and potentially larger tubers.
Optimal Soil Temperatures:
Planting at optimal soil temperatures promotes fast crop emergence, giving potatoes a better start.
Irrigation and Crop Protection:
Using irrigation, proper nutrition, and crop protection methods ensures maximum canopy life and unlimited tuber growth.
Timely Desiccation:
Desiccation at the right stage is crucial to meet market requirements. This practice helps control tuber size and quality.
Nutrient Summary for Potatoes
A correct balance between macronutrients and micronutrients is essential to obtain the best results from potatoes. A deficiency of any single nutrient is enough to limit crop yield. Here’s a review of nutrient uptake and offtake, revealing which nutrients are required at which growth stages and the role of each nutrient.
Macronutrients:
- Nitrogen: Important for leaf and tuber growth. Recycled from the leaf to the tuber during bulking.
- Phosphate: Needed during early growth to encourage rooting and tuber set, and during late season for bulking.
- Potassium: Critical for high yields and maintaining tuber integrity. Utilized throughout vegetative growth, tuber formation, and bulking.
- Sulphur: Needed for all growth stages and reduces common scab.
- Calcium: Ensures stress-free leaf growth and is critical for cell structure during tuber growth.
- Magnesium: Important during later stages of growth, particularly during bulking, to maintain tuber quality.
Micronutrients:
- Boron: Ensures key growth processes proceed unchecked and optimizes calcium utilization.
- Copper: Significant quantities are used, but deficiencies are rare.
- Manganese and Zinc: Important for yield, with zinc playing a key role in nitrogen assimilation and metabolism and starch formation.
- Molybdenum: Important in low pH soils.
