Results of Soil Analysis

Samples of soil have been taken now for two years at the two experimental gardens, and the results are given below.

                            ------- Robin Hood -----   Palliser
                                       M18       M48        M18  
Test               Units    2000      2001      2001       2001  Normal Range
pH                           5.0       5.0       5.0        4.8    5.8-6.5
Olsen P            ug/ml      12        12        20          9      20-30    
Potassium          me/100g  0.45      0.35      0.68       0.15    0.5-0.8
Calcium            me/100g   6.1       6.4       6.0        1.7       6-12
Magnesium          me/100g  1.40      1.45      1.58       0.78        1-3
Sodium             me/100g  0.11      0.14      0.13       0.24    0.1-0.3
CEC                me/100g  18.2      17.4      17.6        6.6      12-25
Base Saturation    %          44        48        47         44      50-85
Volume Weight      g/ml     0.94      0.77      0.81       1.23    0.6-1.0
K/Mg Ratio                   0.3       0.2       0.4        0.2    0.3-1.0

At Robin Hood Bay the first sample taken was in 2000 and not from any particular mound. The sample taken in 2001 was taken from Mound 18 and was from the same general part of the garden area as the previous year. Any indication of soil depletion as a result of growing kumara for one year should therefore be indicated. The sample from Mound 48 taken in 2001 was from the newly cultivated "control" area, and should provide similar results to the sample from the main garden in 2000. The sample from Palliser Bay in 2001 was taken from Mound 18.

In the right hand column appears the normal expected range for this these soil samples.

pH is low in all samples (more acidic than expected)

Phosphorus is also low in all samples

Possium is low in all samples except the newly prepared garden at Robin Hood Bay, and the value for this is at the low end of the normal range. The Palliser soil is very low in Potassium

Calcium is at the bottom end of the normal range for all Robin Hood samples, and very low in Palliser Bay.

Magnesium is at the bottom end of the normal range for all Robin Hood samples, and very low in Palliser Bay.

Sodium values are also fairly low in the normal range, but moderate for the Palliser Bay sample.

Cation exchange values are normal for all Robin Hood Bay samples, and very low in the case of the Palliser sample.

Base saturation values are very low for all samples.

Volume Weight values are normal for all samples from Robin Hood Bay but higher than expected in Palliser Bay. This latter result no doubt reflects the high sand content in palliser Bay and relative;y low humus content.

Potassium/Magnesium Ratios are all rather low.

On the whole, thes results do not inspire much confidence that these soils could be used for kumara horticulure. The Palliser Bay soil in particular appears to be deficient in almost all respects. However, as is clear from the harvest results, and the general performance of these traditional varieties of kumara at these two experimental gardens, the results of soil analysis alone is not necesaarily the best guide to productivity. The kumara plants looked very healthy and vigorous throughout the summer, and produced good yields of tubers, despite the worst drought for 100 years in the second year.

Of special interest here is the low values of potassium. This nutrient is considered to be the key element in the fertiliser programme for the production of modern kumara vaieties, and that even a modest improvement of mild deficiencies in this element can have a dramatic effect on yield.

The Potassium value appears to have gone down a little in the second year at Robin Hood Bay, and it will be interesting to see if this trend continues.