elements. An insufficient supply of phosphoric acid always results in a poorh 

 developed plant, and particularly in a poor yield of shrunken grain. Nitrogen 

 forces leaf and stem growth, and phosphoric acid hastens maturity. 



Calcium, or lime, is a constituent of the stem rather than the seed, and 

 deems to impart hardiness to the plant. It has been noticed that soils containing 

 an abundance of lime usually produce well nourished crops that are capable of 

 withstanding unfavorable climatic conditions, as drouth and early frosts, better 

 than are crops not so well supplied with lime. The exact function of lime is 

 not clearly understood, but it seems to aid in the construction of the cell walls. 

 According to some authorities, its absence is felt in less time than either potassium 

 or phosphorus. It is claimed that a supply of lime is just as essential to the 

 plant in order that it may form cell walls from sugar and starch, as it is for 

 the formation of bone in animals. It also has a very decided influence on the 

 mechanical condition of the soil, and is a liberator of plant food, particularly potash, 

 held in insoluble forms in the soil. 



There can be little doubt that a proper balance in the supply of these four 

 important plant nutrients has a very decided influence on the nature of the plant 

 produced. Each has its own particular work to do, and the absence or deficiency 

 of any one of them will cause the death or the incomplete development of the 

 plant. Moreover, they are absorbed during the early stages of growth; for a 

 cereal crop contains at the time of full bloom all the nitrogen and potash which 

 is found in the mature plant; the assimilation of phosphoric acid continues some- 

 what later. It is thus plain that crops require a good supply of these important 

 constituents of plant growth in a readily available form if they are to make a proper 

 development. 



Differences in Food Requirements. 



Again, plants, like animals, differ very much in their requirements and in 

 their ability to secure that which they need. Cereal crops contain much less 

 nitrogen than legumes, but they have more difficulty in securing it. The autumn 

 sown cereals have both deeper roots and longer period of growth than those sown 

 in the spring, and consequently are better able to supply themselves with the 

 necessary ash constituents. The spring tillage for barley, oats, and garden crops 

 aid nitrification in the soil, therefore these crops have less difficulty in securing 

 nitrogen. Barley, however, has a very short period of growth and is shallow 

 rooted and cannot rustle for its food to the same extent as oats. Corn and the 

 root crops are not only spring sown, but have a much longer period of growth 

 than the cereals, and will thus have command of the nitrates produced during 

 the whole summer. They have fairly good root development, but may not always 

 secure all the potash and phosphoric acid required for the production of a full crop. 



The striking characteristic of all the legumes is the large amount of nitrogen, 

 potash, and lime found in them. However, although they contain fully twice as 

 much nitrogen as the cereals, because of the power they possess of making use 

 of the free nitrogen of the atmosphere, they have comparatively little difficulty in 

 securing the required amount. On the other hand, they have difficulty in 

 collecting potash. Consequently, it may sometimes happen that legumes suffer 

 for want of this constituent on the same soil that cereals would find an abundance. 



It will thus be seen that plants differ widely in composition, range of root, 

 period of growth, and in tlieir ability to gather that which they need from the 



