New Mexico Chile Task Force

Home > Topics > Plant/Foliage > Leaf/Petiole Analysis

Laboratory Analysis for Chile Fertility Management

Without optimum fertility throughout the growing season, chili yield and grower profit will suffer. Soil and plant tissue/petiole analyses are valuable tools to audit crop nutrient conditions. Information gained allows the grower to exactly meet crop nutrient requirements resulting in three significant benefits. First, yield, and quality will not be affected by nutrient imbalance or deficiency. Second, fertilizer will be applied when the crop needs it, increasing efficiency. Third, fertilizer input and cost is maintained at maximum economic yield levels.

PREPLANT SOIL TEST
A pre-plant soil test is invaluable to determine fertility status of the field. The soil test will give three important types of information. First, an appraisal of soil pH, salinity and sodium status is obtained. This information determines if leaching or amendment applications are warranted. Second, reserves of plant nutrients are identified. By knowing carry-over levels from previous crops, soil reserves can be utilized, reducing or re-directing the fertilizer budget. Third, the soil test will identify essential plant nutrient deficiencies. A balanced nutrient supply is fundamental to grow an efficient, high yielding, profitable crop.

LEAF/PETIOLE ANALYSIS
Leaf and petiole analysis monitors exact nutrient levels in the growing crop. Analysis starts with a complete plant tissue analysis when the crop has 3 to 4 mature leaves to assess crop nutrient status and refine the fertility program. A second plant tissue analysis at mid-season for nitrogen, phosphorus, potassium, calcium, iron, manganese, and zinc serves to verify that the fertilizer program is meeting crop nutrient requirements, or allow necessary modifications before peak nutrient demand is reached.

Leaf analysis for secondary and micronutrients is important to diagnose and correct latent nutrient deficiencies. These deficiencies occur with nutrients such as potassium, calcium, magnesium, copper or zinc, which have been gradually depleted through years of crop production. Latent nutrient deficiencies are hidden in that they exhibit no visual symptoms, but definitely limit crop production.

Throughout the growing season, nitrogen and phosphorus levels are measured in eight to ten petiole samples collected at weekly intervals. The petiole nitrate-nitrogen test predicts impending nitrogen deficiency by one to two weeks. Phosphate-phosphorus results are helpful to determine if the plants re receiving adequate phosphorus to balance growth and fruiting.

The following table lists optimum petiole levels for chili throughout the growing season.

Stage of Growth	ppm Nitrogen	ppm Phosphorus	% Potassium
Early Growth	8,000 to 12,000	3,000 to 5,000	6.0 to 8.0
Early Fruit	6,000 to 10,000	2,500 to 4,000	5.0 to 7.0
Fruit Set & Development	6,000 to 10,000	2,500 to 4,000	5.0 to 7.0

Petiole nitrogen and phosphorus levels can be reported graphically to visually assess nutrient status and trend. This information allows timely fertilization before yield suffers.

Optimum levels for other nutrients remain constant throughout the growing season.

Nutrient	Critical Level	Sufficient Range
Calcium, %	0.3	0.4 to 0.6
Magnesium, %	0.8	1.0 to 2.0
Sulfur, %	0.1	0.2 to 0.4
Zinc, ppm	15	20 to 150
Copper, ppm	2	5 to 50
Manganese, ppm	10	20 to 400
Iron, ppm	10	20 to 500
Boron, ppm	2	5 to 55
Sodium, %		< 0.5
Chloride, %		< 0.3

SUMMARY
A fertility management program that employs laboratory testing will benefit the grower in three ways. First, nutrient imbalance or deficiency is identified, maximizing yield. Second, fertilizer application is timed to precisely meet crop needs, increasing fertilizer efficiency. Third, fertilizer input and cost is maintained at maximum economic yield levels.

There are many variables that affect chili production. Weather, is not controllable; insects are sometimes uncontrollable. Information is available to precisely manage crop fertility. By monitoring crop nutrient levels throughout the growing season, one variable--fertility--can be controlled. A crop that receives a balanced supply of nutrients is more efficient, yields better, is more resistant to stress, and will mature earlier, thereby avoiding major insect pressure.