Water and soil testing provides information applicable to a range of management decisions. However, a test is only reliable if the sample is taken correctly and is properly handled after collection, and submitted with the necessary information.
Work Request Forms
A lab report may include recommendations based on the grower’s responses to questions, in addition to analysis of the provided sample. Details requested can include cropping history, yields, fertilizer use, depth of soil and water table, water source, and irrigation system and practice. Provide information about any problems that may have a bearing on the crop. Regarding fertilization recommendations, providing complete and accurate information is essential. Contact a soil testing lab of your choice, then:
- Obtain and complete the Work Request form, to submit with your sample.
- Collect samples.
- Submit samples on the collection day. Refrigerate if delayed.
- When submitting material, be very clear about analyses needed. As an example, when requesting nitrogen analysis, specify TN, TKN, NH4-N, NO3 or NO3-N.
Irrigation water samling is a simple procedure
- To collect a sample, rinse with the sampling water, then fill a 4 – 8 oz. plastic container. Fill to the brim to eliminate air, which promotes calcium carbonate precipitation. Same-day submission is preferred—if stored, refrigerate the sample to minimize precipitation.
- Well water: run the pump for 2 – 4 hours to flush well and to draw from the primary water-bearing strata. If groundwater depth varies over time and is declining, use a portable EC meter to monitor total salinity at 4 -8 week intervals, and submit a sample for lab testing when total salinity increases by 20%.
- Surface water: sample flowing water. Submit first sample for lab testing as a reference point and use a portable EC meter to gain an understanding of salinity fluctuations and to determine the frequency of lab testing.
For a series of videos about sampling your soil: Taking Soil Samples from Your Orchard (Fruit & Nut Research and Information Center)
- Soil probe or shovel; a backhoe or soil auger may be used.
- Clean moisture-proof quart-size sample bags (not plastic)
- Clean, plastic bucket to mix samples
- If collecting samples for microbiology, nematode and pesticide residue analysis, have a cooler on hand, as these samples generally need refrigeration?
A soil sample should include at least 15 – 20 samples from each 20 – 40 acre block. A normal sample should include cores from a depth of 12" – 18". When diagnosing a problem or developing an orchard, cores from a depth of up to 18", 36", or 64" may be recommended. For uniform fields (or for an average of a field), samples should be taken from the entire field. Non-uniform fields should be sampled by taking a composite sample from areas with the same characteristics. Take the samples from the rootzone (e.g. within the irrigated soil) following these steps:
- Divide acreage into 20-40 acre blocks, based on the known orchard variables such as : soil type, topography, crop history, drainage problems, tree variations within the orchard such as rootstock, age and harvest quality
- Walk a zigzag course through the orchard taking 20 – 30 samples. Avoid edges. Remove plant residue from sample spot.
- Take samples at one-foot increments to the depth of rooting, possibly 3 - 5 samples from the same spot.
- Collect one quart of soil and put in a sample bag. If combining soils from multiple sites, mix all samples in a bucket and take one quart from bucket.
- Clearly print on each bag: your identification, the site and sample description.
- Place bags in cardboard box and seal.
- Include a completed work request form supplied by your testing lab.