146 CHAPTER IX 



(4) Freedom from Dark Brown Seed. — With excessive 

 weathering, but particularly with age, the seed assumes a 

 brown colour. The vitality of such seed is low, and often only 

 a very small percentage is viable. If present in large quanti- 

 ties, by no means uncommon, the quantity per acre used should 

 be increased considerably. On the other hand, dark green 

 colour is often a sign of immaturity, especially if the seeds 

 have a tendency to be flat and shrunken as well. 



Inoculation. — Crop failures are sometimes due to the 

 absence of certain bacteria (P. radicicola) in the soil. The 

 plants grow only a few inches high, turn yellow, and then die. 

 In land sown to lucerne for the first time, in which the plants 

 behave in this way, all other conditions being favourable to its 

 growth, and especially if no nodules are formed on the roots, 

 the seed of subsequent sowing should be inoculated, or soils 

 from established fields in which lucerne is doing well should 

 be strewn over the seed-bed and harrowed in without delay. 

 The nodule bacteria of Melilotiis spp., and. it is believed, that 

 of Burr Clover and Yellow Trefoil, are thought to be symbiotic 

 with lucerne as well. It is probable that the nodule bacteria 

 of some wild, commonly occurring legumes in South Africa 

 may suffice for the lucerne plant. On the other hand, it is 

 doubtful whether failures due to this cause often occur in 

 South Africa. The soil method of inoculation is the most 

 practicable. Artificial cultures, generally speaking, have 

 proved unsatisfactory, 



Early Treatment. — The young lucerne should not be cut 

 too early unless smothering by weeds is threatened, in which 

 case it should be mowed as low as possible. If it flowers and 

 starts seeding before the winter sets in, it should be mowed, 

 as the young plants must not be allowed to fruit, since this 

 tends to set back the growth. Young lucerne plants should 

 on no account be pastured, and never when the soil is wet. 



Irrigation. — Irrigate as little as possible before the plants 

 are well established. Depending somewhat on the rainfall, 

 one irrigation, as soon as the crop is taken off, is usually suffi- 

 cient. As soon as the soil permits, after this watering, it 

 should be thoroughly cultivated with heavy cultivators, of 

 which several kinds have been introduced, namely, the Martin 

 Cultivator and Roberts' Lucerne King Cultivator. Disc har- 

 rows are often used where these latter implements are not 

 available. 



