164 



THIRTY-FOURTH FRUIT-GROWERS ' CONVENTION. 



NITROGEN. 



It is evident, I think, that in any plan for fertilization in this semi- 

 arid region, the humiLS content of the soil must be given first considera- 

 tion. If humus is deficient, it must first be supplied. After it is 

 supplied the foundation is laid for the use of chemical fertilizers, if 

 required; but to apply chemical fertilizers in a soil exhausted of its 

 humus ma}^ possibly work more harm than goo.d. 



It is, of course, understood that when we have grown cover-crops and 

 obtained our humus, we have at the same time added materially to our 

 supply of nitrogen.. AVe have added to the soil whatever nitrogen may 

 have been obtained from the air by the cover-crop, and further we have 

 restored the proper conditions for nitrification in the soil. 



Whether the quantity of nitrogen so obtained is sufficient, or. in other 

 words, whether we may rely solely on green manuring for our supply 

 of nitrogen, will depend possibly upon the kind of crop we desire to 

 fertilize. If it be an orange or lemon crop, I think we must certainly 

 add nitrogen in* some other form. Perhaps an analysis of the matured 

 cover-crop may indicate a sufficient quantity of nitrogen for oranges 

 or lemons, but we must remember that it is not in a form to he 

 immediately available. We have turned under a mass of green vegeta- 

 tion which must first be decomposed, and its fertilizing elements changed 

 into other forms by the action of the soil bacteria, before it becomes 

 available to the tree as plant food. It seems unfortunate that our 

 winter cover-crops mature so late in the season that when we turn under 

 this mass of vegetation it is already so late that our trees can not get 

 the full benefit of it in time to help the setting of the new crop of fruit. 

 Just at this time of the year our fruit trees need a suitable supply, 

 though not an excessive siipply of available nitrogen : and. in order to 

 provide the available nitrogen, it has been the practice with many 

 growers to drag down the growing cover-crop, sow a nitrogenous fer- 

 tilizer on top of it, and then plow under the green crop and the fertilizer 

 together. For this purpose either tankage or dried blood will serve an 

 excellent purpose, provided it is put into the ground early enough. It 

 is very desirable for several reasons, and from every point of view, 

 that cover-crops be plowed under early in the season, and no later 

 than February; and I feel sure that the amount of benefit that may 

 be derived from their use will depend very largely upon right manage- 

 ment in this respect. If the plowing has been done early we may use 

 a dressing of nitrate of soda a little later to good advantage, particularly 

 if the spring weather is cold. We know that the processes of nitrifica- 

 tion require a certain degree of warmth in the soil (Snyder says a 

 temperature of 54 degrees to 99 degrees is the most favorable), and it 

 is well to keep this fact in mind when considering whether to use nitrate 

 of soda in the early spring. 



There is another aspect of the matter to be noted, which is that 

 we should not go to extremes in supplying nitrogen. If it be supplied 

 in excessive quantities, plants and trees use it very freely, and in the 

 case of fruit trees, we sometimes get bad results. The quality of 

 the fruit may be injured in this way. of which we have often seen 

 evidence in the orange. And not only is this true, but if the excessive 

 feeding occurs about blossoming time, the growth of leaves and stems 



