Managing Total Soluble Solids (TSS) in melon

The sweeter the melon, the better the end quality.

Sweetness is assessed by Total Soluble Solids (TSS) content. This can be measured by hand refractometers.

The Total Soluble Solid (TSS) content of the melon is expressed as °Brix. It is equivalent to percentage of a reference sugar solution. The TSS is mainly composed of sugars (fructose). Minimum sugar values in melon fruits need to be 8%. Melons with a sugar content of 10-12% have, as defined by US grading standards, a ‘very good’ eating quality. They will also transport well. Those with 12-14% sugar are more suited to some local market. Any melon with a sugar content above 15% is over-ripe.

Crop Nutrition and Total Soluble Solids in Melon

Nitrogen

Nitrogen and Sugar Content

Right amount of nitrogen supply is important to boost leaf growth and sugar synthesis, improving fruit quality. Nitrogen form is particularly important and it is critical to maintain a good balance between ammonium and nitrate forms to maintain fast growth and good crop productivity. Trials confirm significant reductions in nitrogen uptake by leaves and yield losses from use of nitrogen-fertilizers with too high a proportion of ammonium compared to nitrate. Crop quality also deteriorates.

NSource and Yield

Phosphorus

Phosphorus and Total soluble solids

Phosphorus supplies throughout the season help ensure the production of high quality fruit with a high sugar content.

Potassium

Potassium Sugar and TSS

Potassium has a critically important role in ensuring top quality fruit. It plays a key role in the transport of sugars to fruit. Potassium is also very important in ensuring maximum sugar build-up in fruit.

Magnesium

Magnesium and Fruit Quality

Magnesium uptake can be depressed by an excess of other cations (so it is important to maintain a correct balance to avoid compromising uptake). An imbalance of cations will lower sugar content, and pulp and peel firmness.