Butternut fertilizer application tables according to soil types

Butternut¹⁾Featured image by: Butternut Citrouille Courge – Photo gratuite sur Pixabay (Cucurbita moschata) fertilizer requirements can be calculated if you know your soil type and have a good idea of the yield potential of your land and climate. These are basic norms and your specific microclimate and variety can have an influence on the total amount applied. These norms do not take top dressings into account, only the total amount of N, P and K applied during the growth season. The fertilizer can be applied either through the irrigation system or as granular fertilizer. Consult your supplier on the effectiveness of these fertilizers on the various soils to make adjustments to these amounts. Take note that in some countries, like Kenya, the leaves are also harvested and inorganic NPK is mixed with cattle manure to fertilize the crop. Maluki et al. (2021) found that 500 kg∙ha−1 of NPK fertilizer with 2.5 t∙ha−1 of cattle manure was sufficient to improve growth and fruit yield of butternut, even at 2 week leaf harvest frequency.²⁾Martin Maluki, Lenard Gichana Mounde, James Kyalo Mwololo & Elisha Otieno Gogo (2021) Combined use of compound synthetic fertilizer, cattle manure, and frequency of leaf harvest on growth and yield of Butternut, International Journal of Vegetable Science, 27:4, 388-397

Three soils are used in these tables:

• S/SL – Sandy to Sandy Loam
• SL/S – Sandy Loam to Sand
• SCL/C – Sandy Clay Loam to Clay

Butternut Nitrogen (N) application

Butternut fertilizer requirement i.t.o nitrogen is easy. You don’t need a soil analysis just a good idea of your yield potential in the area. Be careful not to overestimate your potential yields as too much nitrogen will also have a negative effect on total yield and the quality of the bulbs. High nitrogen content makes the plant more susceptible to insect damage and diseases.

Butternut Phosphorus (P) requirement – (Bray 1)

Phosphorus fertilizer requirements are based on Bray 1 lab analysis. If another method is used the values must be adjusted. The minimum amount applied is always about 20 kg P per hectare as P is not that mobile and a certain level of P must always be maintained in the soil.

Butternut Potassium (K) fertilization

Potassium requirements are based on a soil analysis and yield estimates. Potassium is extremely important for flower formation and water regulation. Over fertilization can increase the salt content of the soil to such an extent that water uptake is reduced. Note that low nitrogen soil content will impair the translocation of potassium to other parts of the plant. A potassium deficiency in the plant will not be noticed as quickly as nitrogen or iron. Deficiency symptoms occur first in the older leaves as potassium is transferred to younger leaves first. Note that beans are sensitive to salt stress, so too high applications can reduce yields.

Below is the well known soil texture triangle on which the Butternut fertilizer recommendations are based. Most commercial agricultural soils are found in the left bottom corner as they are the most productive and provide the plant with best yield potentials.

Soil textural triangle for Butternut fertilizer requirements.³⁾https://commons.wikimedia.org/wiki/File:USDA_Soil_Texture.svg by Christopher Aragón