piles is noticed, there is a loss of nitrogen. Nitrogen in ammonia 

 is called ammoniacal nitrogen. 



Nitric acid (HN03),or aqua fortis of the drug stores, as its name 

 indicates is also a compound of nitrogen. When nitric acid unites 

 with soda, potash or lime, substances known as nitrates are 

 formed. The mineral takes the place of the hydrogen (H). 

 With soda (Na), nitric acid forms nitrate of soda, (NaNOj.) 



1 6. Nitrogen is closely connected with gj'owth and development, 

 in distinction to stockiness or fruitfulness. — Cereals that grow too 

 much to stalk with immature seeds, usually have too much nitrogen 

 and not enough P^Ojand K^O. A yellow color, and short growth, 

 suggest a deficiency of nitrogen or moisture, or both. 



17. Plaiits cajuiot use all forms of nitrogeri in combination . They 

 use only that existing as a Jiitrate. — Most of the nitrogen that is 

 supplied to the soil in manures and green-crops, is in the form of 

 organic nitrogen, which is not directly available as plant-food. 



However, in a soil in good tilth and having suitable moisture, the 

 nitrogen in the organic material will be changed into nitric acid. 



The nitric acid, uniting with the potash, soda or lime in the 

 soil, forms nitrates. All nitrates are soluble in water, and thus 

 available nitrogen is furnished to the roots. 



This change of the nitrogen into nitric acid and nitrates is ef- 

 fected by germs or microbes, and is called nitrification. 



18. Barn manures supply plant-food. — The amounts of nitro- 

 gen, phosphoric acid and potash in manures are small, not enough 

 in fact to account for all the beneficial effects obtained. Manures 

 are particularly useful in suppl5-ing organic matter, which 

 improves the condition of soils by increasing the moisture-holding 

 power. The more organic matter soils contain, within ordinary 

 limits, the more moisture they can hold. Compare sands with 

 mucks. Consult Lessons i and 2. 



19. Am,endments ay^e sometimes very needful. — Certain substances 

 produce beneficial effects and yet supply little or none of the nec- 

 essary plant-foods. Lime, salt and plaster may be cited- Crops 

 that require potash are often helped by these materials. They 

 contain no potash and yet they furnish it to the plants by help- 

 ing to unlock it from the insoluble silicates. When the oil is 



