Diagnosing the nutritional status of fruit crops is crucial for ensuring their optimal growth, development, and yield. Proper nutrient management is essential to prevent deficiencies or excesses, which can lead to various issues such as poor fruit quality, reduced yields, and increased susceptibility to pests and diseases. The biggest challenge in orchard management is understanding the nutritional requirements of perennial fruit crops by both new and experienced growers. Once we establish the orchard, the routine evaluation of plant nutrient status and soil composition is essential to developing sustainable nutrient management practices.
There are the following tools/observations that fruit growers should utilize to help evaluate the nutritional status of fruit crops:
1) Visual Symptoms
There is really no ‘test’ that can replace the value of walking your rows and spending some one‐on‐one time with your crop. Nutritional deficiencies or toxicities often exhibit subtle symptoms early on that require close attention…things you may not see from the seat of the tractor! While visual monitoring is important, there are disadvantages to only using this approach. The first is that many symptoms of nutrient deficiencies (or toxicities) can look very similar and can even be confused with disease, insect or environmental stresses, therefore it can be difficult to identify the primary problem. The second is that by the time the symptoms are noticed, there has usually been some impact on the crop.
2) Tissue Analysis
Tissue analysis is perhaps the most important tool that growers have in assessing the nutritional status of fruit crops and should be done every 1‐3 years. A tissue analysis provides the grower with a chemical analysis of the concentration of individual nutrients in a growing crop. This can provide a more accurate understanding of nutrient status than visual diagnosis and can identify low nutrient levels before any significant crop impact occurs. Tissue analysis is typically done late in the season and is therefore used to inform nutrient management decisions for the following season.
Collecting a tissue sample
A tissue analysis is only useful if the tissue is sampled properly. Nutrient levels in plant tissues can change dramatically depending on the plant part sampled stage of growth and location on the plant. For each crop, a ‘standard’ nutrient content has been developed based on a particular stage of growth and plant part. Recommendations are made by comparing the submitted tissue sample to the standard; therefore, the analysis is only meaningful if the tissue was sampled at the same stage of growth and from the same plant part as the standard. There are three key factors in taking a proper sample:
Sample at the right time: Be sure to collect the tissue sample at the proper time as nutrient levels in plant tissue can change dramatically throughout the season. For example, N levels are typically quite high in the spring, level off at a lower concentration in mid‐season and then drop off dramatically in late summer and fall before the leaves drop. A leaf sample that is taken during the spring and compared to a standard that was taken at mid‐season will show excessive N and a sample collected in the fall would show a deficiency even if was adequate during the season.
Sample the right plant part: Nutrient levels are also different depending on the plant part sampled. For example, the N content of old leaves is much lower than new leaves because N will move out of the leaf as it begins to die, therefore sampling old leaves may indicate an N deficiency whereas younger leaves will indicate adequate amounts. It is essential to take the sample at the correct time and from the correct plant part to avoid incorrect interpretations. Table 1 outlines the plant part and time of year that should be sampled for different fruit crops.
Take a representative sample: Collect tissue from the entire field rather than from one corner or one row. If you have a large farm, divide it into ‘management units’ that you typically manage in the same way and submit one sample from each unit. Walk through the planting in a ‘W’ or ‘Z’ pattern collecting samples from all areas of the field. Avoid diseased, insect-infested, damaged or abnormal plants. If you are submitting abnormal tissue to diagnose a problem, include a sample of ‘normal’ tissue for comparison. See Table 1 for minimum amounts of tissue to sample. If you have multiple varieties, submit a separate sample for each variety.
Submitting the sample:
Any soil or foreign material should be dusted off the sample, but do not wash the leaves as this can result in the loss of soluble nutrients. If you are mailing the sample, let the tissue air dry for one day to prevent the tissue from moulding during transport. Mail the sample in a paper envelope, do not use cellophane or plastic as these can promote moulding. If possible, mail the samples early in the week to avoid having the sample sit in the post office over the weekend. Be sure to record the sample date, field identification, crop type and any other information that the lab might need for the best interpretation of results.
Crop Stage of Growth Plant Part Min. No. of plants to
sample
Apples, pears,
cherries, plums,
apricots Current seasons shoots, July 1‐15th Fully expanded leaves from midpoint of new shoots 4 leaves from each of 10
trees
Strawberries July 15‐Aug.15 Most recently fully expanded leaves and petioles 2 leaves from each of
20‐25 plants
Grapes Bearing vines, mid‐ July to mid‐August Petioles from leaves
5‐7 leaves from the shoot tip 2 petioles from 40‐75 vines (varieties with
small petioles should have
150‐200 petioles)
Full Bloom (primarily for N and B) Petioles from leaves opposite
from basal (first) flower cluster.
3) Soil Analysis
Soil testing is a valuable tool that can give information about the pH of the soil, and organic matter content and can estimate the supply of nutrients in the soil available to plants. A soil analysis should always be done prior to planting as this is the best time to incorporate necessary soil amendments. Soil pH is a critical factor in nutrient management. Most fruit crops need a well-drained soil with a pH between 6 and 7. Providing the correct soil pH is a critical part of meeting the crop’s nutritional requirements, as soil pH directly affects nutrient availability to the plants. If the soil pH is too high or too low, the nutrients may be in the soil but are not available to the crop, therefore adding more fertilizer will not solve the problem. It is possible to adjust soil pH with the use of lime (to increase pH) or sulfur (to decrease pH), however, this is best used to make minor adjustments.
Taking soil samples every 2‐3 years can help monitor soil pH and ensure you are in the optimal range. Soil analysis is also useful to inform about the amount of organic matter in the soil. Fruit crops benefit greatly from organic matter as it contributes to nutrient availability by improving soil structure, and moisture retention and serves as a nutrient ‘reservoir’. Regular soil sampling can be used to identify trends in nutrient levels of the soil. For example, if you observe increasing amounts of phosphorus in the soil, you may consider reducing the amount of P fertilizer you are applying. Nutrient concentrations reported in the soil analysis have a poor relationship with the nutrient levels in plant tissue of perennial fruit crops. Therefore, soil testing alone should not be used to determine crop nutrient requirements. Soil analysis is most useful when coupled with a plant tissue analysis.
Collecting a Soil Sample
Soil samples should be collected from the same area as the tissue samples. Collect the soil sample to the side of the plants. Do not collect soil samples from the middle between the rows. For tree fruits, take the soil from the area within the drip line but free of vegetation. Cranberry soil samples should be collected throughout the bed. Collect samples from the entire area, do not sample from only one row or section. As you walk through the area, take 8‐10 samples with a soil probe, trowel or small shovel to a depth of about 6 inches. Mix all the samples together and place about 1 cup of soil in a soil sample bag or plastic bag. Record the field identification, crop and sampling date and send to the lab for analysis.
Interpreting Soil and Tissue Analysis Results
The report you receive from the lab will show the concentrations of various nutrients in the tissue and soil and an indication if the nutrient level is deficient, sufficient or high. The interpretation is based on a comparison with a ‘standard’ that has been developed through experimentation on a certain stage of growth and plant part, so the results are only meaningful if the sample was collected properly.
To best understand the nutrient status of the crop, review the tissue and soil analysis together. Providing nutrients efficiently and effectively to fruit crops is a challenging yet critical component of crop production. Routine soil and tissue analysis can allow you to monitor the nutrient status of the crop, prevent deficiencies, evaluate current production practices and reduce unnecessary nutrient applications.
4) Growth and Yield Monitoring
Keep records of the growth patterns and fruit yields in your orchard. Changes in growth or yield can be indicators of nutrient-related issues. Consistent monitoring allows you to detect problems early.
5) Foliar Nutrient Sprays
Conduct foliar nutrient sprays if necessary to provide a quick source of nutrients to the plant. Foliar sprays are especially useful in correcting acute nutrient deficiencies.
6) Nutrient Management Plan
Develop a nutrient management plan based on the results of soil tests, leaf tissue analysis, and other diagnostic methods. This plan should outline the types and amounts of fertilizers or soil amendments needed to address specific nutrient issues.
7) pH Adjustment
If soil pH is out of the optimal range for the specific fruit crop, consider adjusting it. Lime may be added to raise pH, while elemental sulfur can be used to lower pH.
8) Organic Matter
Ensure that the soil has adequate organic matter content. Organic matter improves nutrient retention and water-holding capacity.
9) Integrated Pest Management (IPM)
Implement IPM practices to manage pests and diseases. Some nutrient-related issues can be exacerbated by pest damage.
10) Regular Monitoring: Nutrient management is an ongoing process. Continuously monitor the nutritional status of your fruit crops throughout the growing season and adjust your practices as needed.
11) Professional Consultation
If you are unsure about diagnosing or addressing nutrient issues in your orchard, consider consulting with a local agricultural extension office or a professional agronomist who can provide tailored advice.
Nisar Ahmed Bhat is PA to Vice-Chancellor, Pool Officer, I/C Guest House, I/C NR(RA)CC, Sher-e-Kashmir University of Agricultural Sciences and Technology – Kashmir (SKUAST-K). He can be reached at [email protected]
