OCR Text |
Show MANURING PRACTICE GOOD FOR POTATOES i B Geo. Stewart, In Charge of Flelr" Crops, Experiment Station, Utah Agricultural College. Manuring practices vary consider ably. In the East commercial fertilizers ferti-lizers are in general use, especially in the trucking sections. Phosphorus, potash, and nitn -gen are frequently applied. This form of manuring hu noi yet become general in the West. Potato growers of Utah and adjacent states depend on farm manure, and aod-mutter and for the fertilizing elements. Occasionally late fall or karly spring growth of alfalfa la turned under, but the usual practice is to make hay of this and return to the land the manure made by the animals to wihlch the hay is fed. With bo many rattle on the summer ranges this Is probably the most profitable prof-itable system of fertilizing the land. The funotions of organic matter of farm manure nd sod is pr'nelpally to supply organic matter. In the end, H -mplete decomposition results and the fertilizing elements are added to the soil in a readily available form. Important, however, as the fertilizing elements may be, the Indirect effect is still more Important. Coarse manure man-ure and large roots are hindrances to cultivation and irirgation, but under favorable conditions, these are soon educed to fine particles which are still undergoing active decay and which mix readily with the sil particles. par-ticles. Organic matter in such condition con-dition Is valuable in two distinct ways: (1) by increasing the water-holding water-holding capacity, and (2) by creating a condition of medium porosity In the toll. Increases water-holding capacity: Decaying organic matter absorbs water much ns does a sponge. Because Be-cause many of the particles are hollow, hol-low, Uie surface to which films of water can cling is much greater than on solid soil particles of the same volume. In addition organic matter 1 ntains a substance called humic acid which has the pow-er of holding hold-ing many times its own weight of "Titer in a loose chemical combination. combina-tion. Controls porosity and aeration: Besides, organic matter loosens clay soils and renders them porous. It has the opposite effect on coarse sands and otherwisu extremely porus soils, in which it serves as sort ot binder as well as a retainer of water. It is common knowledge that wet sand, even it nearly pure and very coarse, will hold together with greater great-er tenacity than the same sand when deprived ' of dts mjotsture. Organic matter, therefore, consolidates loose soils both by supplying a binding agent and by furnisning a retainer of water. A high degree of looseness In clays and a high degree of consolidation consoli-dation in sands increase the water-holding water-holding powers of such soils. These conditions also encourage more desirable de-sirable aeration and uniformity of emperature. Compact clays have too little pore space to hold much water to permit the easy exchange of passes between the soil and the atmosphere. Hoots and bacteria both need air oxygen also helps in rendering mineral plant-foods soluble. Sandy soils are likely to oe too hot and clayey soils too cold. The extra moisture and the consolidation in sandy soils moderate the temperature tempera-ture of these soils and thereby decreases de-creases evaporation, in heavy soils the increase of pore space encourages more through ventilation. As the water wa-ter content increases to about medium med-ium the pore space increases. If more water is added the volume decreases de-creases and consequently the air pace. It is at this point of greatest volume that soils aerate most readily and consequently warm up most rapidly. rap-idly. Eoots can penetrate more easily and more deeply because air is available avail-able at greater depths and because there Is less resistance. In all respects re-spects the soil is then In the most lavorabl condition for plant growth. On this account this condition In soil Is known as the optimum (Latin word meaning the best) water content. Actively Ac-tively decaying organic matter tends to bring all soils to this desirable condition. |