-•:;•_' i m: farmers' handbook. 



SECTION VI£. 



Leguminous Crops* 



Every farmer is now familiar with the group of plants known a< legumes 

 (so called because their " fruit " which contains the seeds is a legume or 

 pod). These plants are of the highest value and possess characteristics 

 that distinguish them from all others, notably the high protein content 

 of their seed, the excellent feeding value of their whole vegetative system, 

 and their capacity for storing nitrogen in their roots and thereby leaving 

 the soil actually enriched in that important item of plant-food. 



In New South Wales legumes are grown for various purposes : Lucerne 

 tor hay, held peas, vetches, and cowpeaa for green fodder and hay, and also 

 for green manuring and soil renovation, and garden peas and beans for the 

 vegetable market and home use. Their place in our farm practice, indeed, 

 is even larger than might be apparent at first sight, for the " herbage " that 

 springs so abundantly on wheat lands when these are " left out," and that 

 is so highly esteemed as pasture, consists largely of trefoils, which are as 

 much legumes as lucerne or clover. 



The secret of the value of these plants to the farmer is the possession of 

 a source of plant-food that is not accessible to most other plants, particularly 

 not to cereals. The practical experience of hundreds of years led farmers 

 of past generations to believe that leguminous crops possessed some peculiar 

 power of making succeeding crops grow better, and it was not till the last 

 twenty-five or thirty years that this could be explained. It is now known 

 that association with certain bacteria in the soil enables legumes to make use 

 of the air in a way that other plants cannot. This association is one 

 of mutual helpfulness, or symbiosis, the bacteria requiring considerable 

 quantities of certain kinds of food that are generously supplied in the plant 

 juices of legumes, while the plants derive from the bacteria, in some way 

 not yet fully understood, a supply of nitrogen that the bacteria have taken 

 from the air and built into nitrogen compounds within their own cells. It 

 is supposed that the nitrogen compounds thus manufactured by the bacteria 

 are diffused through the cell-walls and absorbed into the general circulation 

 of the plants, where they are used for the building up of the protein com- 

 pounds that are characteristic of the legumes in whatever form they are 

 considered. The presence of these bacteria is indicated by the development 

 on the roots of the little growths now universally known as "nodules.'' 

 These little swellings vary from the size of a pin-head to the size of a small 

 pea, and they may sometimes be seen by carefully digging up a plant with 

 as many of the small roots as possible and then washing away the earth in 

 a gentle stream of water. 



There is unfortunately an impression amongst farmers that if /the 

 leguminous crop is removed from the land and the roots with their nodules 

 remain, the soil is thereby enriched in nitrogen. It must be clearly under- 

 stood that the nitrogen taken from the air by the organisms does not exist 

 in the nodule-, bur is made use of and distributed throughout the plant. 



