The dirt on orchard soils

A soil-testing project on Goulburn Valley orchards has found a high level of phosphorus. The tests, conducted under the Commonwealth Government’s Caring For Country program, found about 80 per cent of the samples contained phosphorus levels above what was needed for a healthy soil.

While not considered dangerous to trees, the high phosphorus results could mean orchardists in some cases are wasting money on applying phosphate.

Orchardist consultant and project co-ordinator Henry Schneider found mixed results for the report card on irrigated soil health for the 401 blocks.
‘‘The report card on these orchard blocks surveyed in the winter of 2012 is good news for some of the soil tests; but for others a new fertiliser management strategy needs to be assessed,’’ Mr Schneider said.

The program has the support of the Ethnic Council of Shepparton, which has a history of involvement with agricultural programs in culturally diverse farming areas. The project assessed key orchard soil factors such as salinity, soil pH, phosphorus (Olsen P test), organic carbon, boron, potassium calcium and lime.

Mr Schneider said the good news was there were no salinity issues as yet in the top 150 mm of soils sampled. However, he said about 20 per cent of the blocks sampled needed to be watched and monitored annually.

Mr Schneider said the phosphorus results were a little unusual. He said about 17 per cent of samples were around the soil levels that were needed, while all the others, about 80 per cent, were higher than required.

‘These high levels of phosphorus are not toxic to the fruit trees,’ he said.

‘They just represent the option of an alternative fertiliser management strategy, which focuses more on correct timing of nitrogen fertiliser and omitting phosphorus until a further soil test, or preferably a leaf analysis, indicates that phosphorus levels have slid into the lower but adequate ranges.’

A major impact on soil fertility is pH and Mr Schneider said 66 per cent of the samples tested were in the adequate range, while about 12 per cent were a little too high.

For boron, only about five per cent of blocks in the survey had adequate levels, which was the lowest results for all nutrients tested. Boron deficiency can lead to poor flower set and low seed counts in apples, and in severe cases can cause bark measles in apples. Mr Schneider warned that boron could be toxic if not carefully applied.

‘Leaf analysis is the best way to check that foliar sprays are adequate,’ he said.

Potassium levels were in the desirable range for 45 per cent of blocks, and 22 per cent were in the high or excessive range. A leaf analysis test will tell how well a tree can extract its potassium requirements. More than 80 per cent of surveyed blocks were in the desirable range for calcium.

An additional outcome from the survey is that each participating grower had the opportunity to discuss the soil test results and orchardist Gurmeet Singh said he had changed the way he applied fertiliser since seeing the results on his 15 ha Shepparton East block.



Article and image courtesy Shepparton News



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