A soil-depleting crop may be defined as one that causes the destruc- 

 tion of organic matter or the loss of minerals in excess of those carried 

 away in the crop. The organic matter is lost because 

 Soil-Deplet- the crop requires excessive cultivation. Minerals are 

 ing Crops lost because the crop leaves the soil exposed to erosion. 



The term is a relative one; some crops are more soil 

 depleting than others. Small-grain crops allow some erosion and, 

 whether harvested or not, are never true soil-conserving crops. There 

 is, however, less soil depletion than when corn or cotton is grown. 



If a small-grain crop is interplanted with clover or lespedeza and the 

 legume covers the ground by the time the grain is harvested, prob- 

 ably as much organic matter will be left in the soil as is lost. There 

 will be even more left in the soil if the grain is pastured down. A 

 combination of a small-grain crop and clover or lespedeza pastured or 

 left on the land tends to conserve the soil. 



All the lime, phosphorus, and potash in the body of a plant has been 

 taken from the soil in which it grew; there is no other place the plant 

 can get it. If these plants are grazed or otherwise 

 Depletion of removed from the soil on which they grow, just so 

 Minerals much lime, phosphorus, potash, and other minerals as 



they contain are removed from the soil. If the plants 

 are left to decay in place or are turned under, the minerals they con- 

 tain are returned to the soil. The mineral content of soils may be 

 depleted by cropping, by leaching, or by erosion ; it may be conserved 

 by proper farming practices that reduce leaching and erosion, but it 

 cannot be increased by any form of cropping. When minerals are 

 needed they must be added. All harvested crops remove something 

 from the soil and insofar the soil is depleted. Cotton and corn are 

 classed as soil-depleting crops; most hay crops as soil conserving. 



However, from the standpoint of the plant food removed, a cotton 

 crop is no more soil depleting than a crop of Bermuda grass hay. 

 An average cotton crop of 204 pounds of lint and 368 

 Plant Food pounds of seed will remove from the soil about 13.3 

 Removed by a pounds of nitrogen; 5.3 pounds of phosphoric acid; 5.4 

 Crop pounds of potash, and 1.3 pounds of lime. This is 



assuming that leaves and stalks go back into the 

 ground (fig. 1). For Bermuda grass hay, the corresponding figures per 

 ton of hay are 23.36, 4.0, 28.4, and 9.6 pounds, respectively. A crop 

 of seed cotton removes from the soil a little more phosphoric acid but 

 less potash, lime, and nitrogen than a crop of Bermuda grass hay. 

 From the standpoint of the amount of plant food removed, cotton is 

 therefore no more soil depleting than hay. The fact that hay removes 

 from the soil a comparatively large amount of plant food was also 

 pointed out by J. S. Cutler, conservator for Region 3 of the Soil 

 Conservation Service, who showed that a 4-ton per acre yield of alfalfa 

 removed more nutrients than a 50-bushel per acre yield of corn. 



Cotton and corn are considered soil depleting because of the chance 

 they give for erosion. If they could be grown under conditions that 

 eliminate erosion, they would be no more soil depleting than hay. 



The quantities of minerals removed by plants are small in com- 

 parison with those lost by erosion, but on the soils less well supplied 

 with minerals the steady withdrawal of plant food through the years 

 has a considerable effect and cannot be ignored. Old grass pastures 

 become poorer with the lapse of time because the constant removal of 



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