178 THE MONTHLY BULLETIN. 



retailers and consumers of the countr}-, as it will speedily be through 

 the Exchange system of national advertising, with a reasonable tariff 

 there should be no difficulty as the California crop increases in gradu- 

 ally forcing the foreign lemon out of American markets, resulting in 

 an American grown crop supplying an American market, which will be 

 as it should be. 



CULTIVATION AND COVER CROPS.* 



By W. M. Mertz, Superintendent of Cultivations, Citrus Experiment Station, 

 University of California, Riverside, California. 



Cultivation, meaning the stirring of a soil to accomplish aeration 

 and to prevent evaporation, is a practice which has been in vogue 

 among agriculturists since the beginning of agriculture. Under the 

 semiarid conditions of the southwest, cultivation has assumed a more 

 important role than in most of the sections of this country. Water 

 has, in reality, been the limiting factor with most of the cultivated land. 

 Thus certain cultivation was necessary to conserve this valuable ele- 

 ment. Investigations carried on some little time ago showed that cul- 

 tivations to a depth of four to six inches materially lessened the evap- 

 oration of soil moisture and in this regard were much superior to 

 shallow cultivation, such as is adapted to eastern humid conditions. 



Cultivation, in that it aerates the soil, tends to increase the oxidation 

 of organic material. The high temperatures met with during the sum- 

 mer months in this State also make for the increase in the oxidation 

 process. Thus, in the conservation of water the excessive cultivation 

 has caused a considerable loss of organic material in many of our soils. 

 In fact, there are many who believe that the loss of organic material by 

 such frequent cultivation, is more serious than the loss of water caused 

 by systems employing less frequent cultivations. As with all things, 

 we usually find a happy medium, which is better than going to either 

 extreme. Too frequent cultivation is extremely exhaustive of organic 

 material; too infrequent is just as exhaustive of the irrigation water. 

 The type of soil, the location and the crop will all have a bearing on 

 the frequence and depth of cultivation. In the heavier types of soil, 

 cultivations are usually more frecfuent while the lighter soils are fre- 

 quently well protected from evaporation by a single cultivation after 

 each irrigation. 



As can readily be seen, cultivation and irrigation are two factors of 

 our orchard management w^hich are practically inseparable. Thus, on 

 soils which require irrigation every three weeks, cultivations as frequent 

 as this are demanded. On heavy clays irrigations are frequently made 

 at as long intervals as every ten or twelve weeks. This interim is 

 usually too long to expect one cultivation to maintain a reasonably 

 efficient mulch. Again, the clay soils do not crumble and make as 

 good a mulch in one cultivation as the sandier soils. It has seemed 

 good practice on such heavy soils to cultivate two or three ways as soon 

 as the land is in proper shape to work. Again, another cultivation or 

 possibly two, is often advisable before the land is again irrigated 



* Address before special apple meeting, San Bernardino, Cal., February 19, 1916. 



