Soil samples will be tested for their physical and chemical properties to determine their suitability for planting trees. The test results will be used to determine if corrective measures are needed. Soil samples should be a good representative of the area, therefore, soil sampling is an important step. It is a waste of time and budget if the soil sampling was not conducted properly, the output data would not be useful. Soil sampling at Mae Moh site was conducted prior to planting the trees. The samples were collected at planting holes. Sampling tools were kept clean and clear from dirt, fertilizer and any chemical. The tools include driller, spade, shovel, hoe, plastic bags, rice sac, bucket, plastic sheet, cord, permanent marker, sample box, nails, elastic etc. Soil morphology and structure was hard to identify at the dump site, sampling for soil chemical properties testing, therefore, spread through out the planting site (Figure 1) to cover for all the species. The data will be able to indicate the future soil management and trees tending. The diagram from the figure 1 shows that in each replication, 4 soil samples were collected from planting hole number 27, 34, 41 and 48 of each species 1. From each hole the sample was collected from 3 levels at 0-25, 25-50 and 50-≤100 cm depth. There were 72 samples from 1 planting block or 432 samples all together.
Each sample was carefully separately collected at least 1 kg per sample. Information included Project title, collecting site, sampling spot, deep level and collection date for each sample were labeled on sampling container (Figure 2). Photographs of sampling procedures of planting hole numbered 27 of every replication were taken to observed soil color or other information for future references.
Figure 1 Diagram indicates soil sampling spot of rep 1 as yellow mark, other replications are also collected at the same spot
Figure 2 Soil sampling procedure
The soil samples were left air-dry under room temperature (Figure 3) before sieving out rock and gravel. Soil physical properties were evaluated for soil texture and gravel ratio. 0.5 kg of sieved soil per sample was then kept in plastic bag (Figure 4.) for chemical properties test in the lab.
Figure 3 soil samples were left air dry before sieving.
Figure 4. Sieved soil samples were kept in plastic bags waiting for being mixed before sending to the lab.
Soil sample from the same depth in the same row in each replication were mixed as show in the table 1. 432 samples were then reduced to 108 samples. The mixed sample relate to plant species. 500 gram was taken from each of 108 mixed sample to test for its chemical properties (Figure 5). Medium mixed to replace in planting holes were taken for testing. 3 samples were collected, left to dried and mixed. 1 sample of 500 gram of mixed medium was sent to the lab for testing. The chemical properties to be tested are pH, OM, CEC Exchangeable K, Ca, Mg and Na.
Table 1. Each planting block, each soil mixed number was taken from 4 planting holes of the same depth and the same row.
Figure 5 Mixing of soil samples and the soil sample ready for analysis