Ass. Prof. Dr. Wathib Shukri Alnuaymy

Agricultural workers used to tillage the soil to provide a suitable bed for seedling rise and seed germination, as tillage the soil loosens it and reduces its resistance to penetration.

Human has known this process since the beginning of his conversion from hunting to provide his food by agriculture, and he used stones and wood for that, then machines made of iron to tillage that drawn by horses and oxen, all the way to those pulled by pullers. But is the tillage process an acceptable process from a scientific point of view?

Irrigation specialists often ask their famous question, “When do we irrigate and how much water do we add?” The scientific references have elaborated the answer to this question, and in talking about tillage, I had to ask when to tillage the soil and what is the amount of that tillage. The scientific references still did not answer this. The question is adequate. It seems to me that the answer to this question still requires a large amount of research related to tillage. However, I will try to answer it with the available information.

Soil tillage is a concept closely related to the properties and physical characteristics of soil such as the apparent density of the soil, the construction of the soil, its saturated and unsaturated water conductivity, aeration and heat, which in turn are a product of soil construction and indirectly by sterilizing the soil with sunlight to get rid of some unwanted microorganisms of soil. The concepts of physical, chemical and biological soils are related to each other. At a time when we need to tillage the soil in order to reduce its apparent density, we are working on destroying the soil structure (the regularity and association of the initial soil particles in an engineering way with a carminative material), which in turn will lead to the deterioration of the rest of the soil properties associated with it, such as the density of the soil itself and thus re-compacting it after the first or second irrigation after tillage (soil subsidence), which causes a bad redistribution of soil voids and pores, which will affect the movement of water and solute, which will lead to not making full use of the water and the added fertilizers, either for not retaining water and solute in the soil body within the soil volume affected by the roots or the resulting decrease in dissolution and movement Plant nutrients in the soil.

The most important physical characteristic that affects the movement of dissolved water in the soil is the ratio and distribution of the geometric soil pores, and they are a direct product of building the soil, and maintaining it will remain a difficult task while conducting the tillage process. For soil, it would be an appropriate criterion for workers in agriculture, at least at the present time, to make the decision to tillage. To answer the first part of the question when to tillage the soil, the apparent soil density, which is less than 1.3 Mg m^-3 (the appropriate soil density for most crops is 1.2-1.3 Mg m^-3) It is not necessary to carry out the tillage process, while increasing the density of the apparent soil from this limit will determine the answer to the second part of the question what is the required amount of tillage. Conventional tillage and deep tillage.

When it is intended to grow plants that do not need to cover their seeds with soil, such as some pasture plants and weeds, and the apparent soil density is less than 1.3 Mg.m^-3, then zero tillage will be an appropriate option, while if the seeds of plants need to cover with soil and for the same soil density above, we must think about the minimum tillage, using seedlings, and the less scratching the soil is with this soil density, our choice is the best in order to preserve the building of the soil from destruction and deterioration. Also, the use of the rake in a non-orthogonal way will also be a suitable option, which is the practice of the farmers of blood-wheat in our country, while when it increases Apparent density of less than 1.3 and less than 1.45 Mg m^-3 The option of tillage with rakes to a depth of 10 cm in a perpendicular manner may be acceptable, while if the density of the apparent soil exceeds this range, resorting to traditional tillage using tillage that achieve a depth of 30 cm is a must, especially when The apparent density of the soil has reached the limits of 1.6 Mg m^-3, while the resort to deep tillage is linked to the presence of a layer that is impermeable to water (the hardpan), and this type of tillage needs C to huge tillage machines pulled by heavy equipment such as turnbuckles or saw tillage, which may achieve a depth of more than a meter. The geometric distribution of soil particles became at its worst.

This is what I will talk about in another article under the title of Physical Soil Fertility, God willing