. . . . . . . . refers to a condition in which a crop needs more of a given nutrient yet has shown no deficiency symptom

Hidden Hunger refers to a condition in which a crop needs more of a given nutrient yet has shown no deficiency symptom. With most nutrients on most crops, significant responses can be obtained even though no recognizable symptoms have appeared.
Testing of plants and soils helps plan or modify plant-nutrient programs to avoid this problem of hidden hunger in subsequent crops.