Coconut palms yielding poorly on sandy or poor soils

Palms that look alive but carry few bunches and small nuts are a common sight on poor, sandy land. The palm is often simply not getting enough water and nutrients from the soil it is growing in.

Research on coconut soil fertility describes red, lateritic and sandy coconut soils as suffering from soil acidity, low cation exchange capacity (CEC) and poor nutrient reserves.^[1]

• Soils that hold little. Sandy soils have poor nutrient-holding capacity and low CEC. In these soils organic matter is the main determinant of fertility and nutrient storage, and nutrients leach easily.^[4]
• Potassium shortage. Coconut is a heavy feeder of potassium and needs a constant supply, and potassium supply in acid soils is poor. Potash also regulates the palm's water economy, which matters when water is limited.^{[1, 2]}
• Magnesium and other secondary nutrients. Magnesium has been linked to more female flowers, better setting and more nuts per bunch. Secondary and micronutrient deficiencies are emerging as yield-limiting factors in coconut.^{[1, 2]}
• Moisture stress. Soil and water conservation measures have improved coconut yield on sandy soil and reduce run-off and erosion losses on slopes.^[1]

• Conserve moisture. Mulch the basin with coconut husk, coir dust or coconut leaves, alongside organic manure or green manure. Bunding and terracing help on sloping land.^[3]
• Build up organic matter. Organic materials such as leaves, cattle manure, coir dust or coconut shreddings applied to the planting pit and palm basin help palms establish in sandy soils.^[2]
• Keep potassium and magnesium supplied. Base the rates on soil and leaf analysis rather than a fixed recipe, and split applications on sandy soils where nutrients leach.^{[1, 2, 4]}
• Use leaf analysis as well as soil tests. Some deficiencies can be recognised from symptoms, but leaf nutrient analysis helps confirm what the palm is actually short of.^[2]

NEXGROW is a bio-organic, phosphate-solubilising fertiliser, and coconut is one of the crops in its booklet. The booklet describes it as converting insoluble soil phosphorus into forms the palm can absorb (adequate phosphorus is essential for flower initiation and development), supporting root growth and photosynthesis, and helping tolerance to stresses such as drought.

Its organic matter fits the soil-building side of managing poor soils. It does not replace potassium or magnesium where a test shows they are short. Rates below are taken directly from the booklet.

Test soil before planting or rehabilitating a coconut block, and use leaf analysis on bearing palms that underperform. On sandy, acidic land the test shows pH, CEC and which nutrients are short, so potassium, magnesium and lime go where they are needed.^{[1, 2]}