Every farmer dreams of high profits. Unfortunately, this dream is shattered by misinformation about farming, which many agronomists mainly use. The misinformation is skewed towards promoting sales of the different farm inputs.
Some of these myths discourage the use of inputs or practices that can, in a real sense, lower the cost of production. “Don’t use manure in watermelon farming but instead use fertilizer only” is one of the many myths and lies that are chiefly told to promote the sales of inorganic fertilizers. The question is, “What is wrong with manure?”
The major challenge with watermelon farmers is poor growth and low yields due to either nutrient deficiency or excessive application of nutrients, especially nitrogen and Phosphorus.
Most watermelon farmers have complained of excessive vegetative growth, low yield, and poor fruit quality when using CAN 40KgN/acre fertilizer rates and TSP at 50Kg P2O5 /acre.
This article dissects these “lies—do not apply manure to watermelon farming” with data from trials carried out in two consecutive seasons in Kenya. What is worrying is that no substantive reason or data is given to support this ‘lie’.
The Farmworx team dove into this issue to understand if there is any benefit in the quality of fruits and income earned from using manure or inorganic fertilizers. Data from research by the Department of Crop Science at Pwani University showed stunning results.
Importance of significant nutrients to the crops
One way of increasing nutrients drawn from the soil through harvested crops is to use organic manure blended with inorganic fertilizers. However, the use of inorganic fertilizers is currently limited by their high cost and unavailability when needed.
It’s important to understand that manure and inorganic fertilizers directly and indirectly provide the soil’s required nutrients, nitrogen and Phosphorus.
An adequate nitrogen supply is associated with a high photosynthetic rate, vigorous vegetative growth and deep green colour of the leaves. Nitrogen increases leaf and shoot growth, number of leaves and plant weight over time.
Phosphorus is essential in root development, energy transfer, and plant quality improvement.
According to trials, the application of cattle manure and CAN fertilizer, either singly or in combination, significantly increased the marketable yield, fruit number, and fruit weight of watermelon compared to zero application.
Agronomy practices in the trials
Manure and DAP fertilizers were applied at planting by placing them in planting holes and thoroughly mixing them with topsoil. Plant spacing was 1.6 by 0.6m, and the plant population was 5,600 per acre.
CAN fertilizer was applied four weeks after planting and again three weeks later.
Four weeks after sowing, 800ml Thunder was sprayed alternately with a 30ml belt per acre, which was repeated at the sixth and eighth weeks to control melon fry.
During the last three weeks of harvesting, the fruits were turned regularly and covered with dry glass to reduce sun scorching and ensure uniform fruits and appealing skin colour.
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Effects of supplementing fertilizers with manure on fruits quality
Using manure at 1.3 tons per acre reduced fruit thickness by 30% when fertilizer rates were applied at 25kg phosphorus (P2O5) and 25 kg Nitrogen per acre. The manure application rate reduced fruit thickness by up to 10.3% with no inorganic fertilizer application.
After 2.5 tons of cattle manure, 25 kg of nitrogen, and 25kg of Phosphorus (P2O5) were applied per acre, fruit firmness increased by 28%.
The lowest cost-benefit ratio of 2.4 was realized when no organic manure or inorganic fertilizers were applied. The highest cost-benefit ratio of 7.2 was realized when 3.8T of cattle manure, 50 kg of nitrogen, and 50 kg of Phosphorus (P2O5) were applied.
Therefore, farmers can apply a high rate of cattle manure at 3.8 tons and supplement it with low rates of inorganic fertilizers (50kg Nitrogen and 50 kg Phosphorus P2O5). Where manure is scarce, farmers should apply low rates of manure of 2.5 tons per acre and supplement it with high rates of inorganic fertilizers (100kg Nitrogen and 100 kg Phosphorus (P2O5)
Therefore, it is wrong and misleading to tell farmers not to use cattle manure but artificial fertilizers only in watermelon farming. Returns increase with an increased rate of supplementation of cattle manure with inorganic fertilizers, nitrogen and Phosphorus.
However, it’s good to note that the results may vary depending on the variety planted and the management.
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