ORCHARD ROTES

Te Awamutu Courier, Volume 53, Issue 3799, 24 August 1936, Page 3

ORCHARD ROTES

GREEN MANURING. The loss of soil organic matter is a major problem in agriculture the world over. This loss is indicated by the unhealthy condition of the trees which show that, despite every effort to fertilise the soil it has graduallybecome poorer and infertile. In citrus trees, a leaf disease, known as “Mottle Leaf” frequently makes its appearance. This disorder is intimately associated with a deficiency in soil organic matter. Die back or exanthema may develop and one disease follows another.

Humus, a product of the decay of organic substances, is one of the most tile soil and, generally speaking, is present only in inadequate amounts •n most of our citrus soils. Except on alluvial lands periodically improved in fertility by flooding, the orchadist must consider the maintenance or improvement of the soil fertility if he is to harvest good crops. When the soil has been under cultivation for some time without any addition to the humus supply, it will be noticed that it differs markedly in physical condition from its virgin state. The heavier loam soils are more inclined to run together with rain and bake more readily when drying. This is due to a large extent to the loss of organic matter, or humus. This loss takes place more rapidly in warm, moist, districts, and where catch-crops are intercultivated. In effect, the clay particles have a tendency to break down into fine dust, which finds its way into the interstices between the soil particles, and, with the diminishing supply of humus, tends to cement them, excluding air and water. Sandy soils lose their organic matter even more rapidly than loam soils under cultivation, and trees and plants suffer on such soils. In the absence of adequate supplies of humus, their tendency is to heat up, and soil moisture is lost through evaporation, ahd particularly by percolation beyond the reach of feeding roots. In the absence of bulky, farmyard manure, the maintenance and improvement of the soil may 'be carried out by growing and turning under green manure crops. Not only do such crops build up the physical conditions of the soil, but their presence reduces soil losses by erosion daring periods of heavy rainfall.