88 Pecan-Growing 



Similar combinations with other cover-crops may be ar- 

 ranged when two are grown on the soil each year. The 

 organic content usually can be kept up if one of them is 

 turned under, while the other may be cut and removed for 

 hay. However, unless the grower is reasonably sure that the 

 humus and plant-food content of the soil are being maintained, 

 both cover-crops should be turned under each year. 



Commercial fertilizers. 



The chief function of each of the three essential fertilizer 

 elements, phosphoric acid, nitrogen and potash, in the nour- 

 ishment of plants should be understood in order that they may 

 be applied to the soil more intelligently and economically. 

 Other elements, as sulfur, iron, calcium, and magnesium, are 

 essential to growth, but since they are usually present in the 

 soil in sufficient quantities to supply readily the needs of the 

 growing plants, they need not receive serious attention in 

 compounding a suitable fertilizer mixture for pecans. 



The function of phosphorus is to hasten maturity and in- 

 crease the percentage of seed or fruit in proportion to the 

 size of the plant. It also stimulates root growth. Phosphorus 

 is taken into the plant in solution, as calcium phosphate. It 

 is assisted in circulating through the plant by magnesium, 

 and combines in the cells with nitrogen, sulfur, carbon, hydro- 

 gen, and other elements to form protoplasm. Phosphorus 

 applied to soils containing large amounts of nitrogen has a 

 decidedly balancing effect in preventing the plant from going 

 too much to leafy and woody growth. 



Nitrogen promotes a vigorous growth of leaf, stem, and 

 wood. It sometimes hastens blooming but delays maturity. 

 It is taken into the plant, in solution, as nitrates, and pro- 



