55 

 of first and third crops were greater in cropping patterns HM-HM-HM, 

 M-MM-LM, and HI4-LM^!4M than in LM-LM-LM. Cropping pat^ern LM-LM-LM 

 resulted in pH above 6.0 after the third crop, whereas cropping patteims 

 involving combinations with HK crops resulted in pH below 6.0 (Table 8). 

 In all cropping patterns, soil pH tended to equilibrate to its Initial 

 level after each year of cropping. The low soil pH in HM-HM-HM can be 



attributed to replacement of H on the exchange complex and by hydrolysis 



3+ 

 of exchangeable Al and hydroxy Al resulting from high management lerti- 



lizer application rates. 



Soil organic matter . Soil CM content decreased with successive 

 cropping in all cropping patterns except for cropping pattern LM-LM-LM 

 (Table 9) . Average reductions in soil OM content were greater with 

 cropping pattern HM-HM-HM thain other cropping patterns. In contrast, 

 cropping pattern LM-M-LM resulted in increased soil OM content from 

 0.86 to 0.94?o after harvest of third crops. After harvest of third crops, 

 cropping pattern HM-HM-HM resulted in significantly lower OM con-cent 

 among ^he four cropping patterns (Table 9). For each cropping pattern, 

 the effect of high fertilizer levels generally resulted in greater OM 

 contents after harvest of second and third crops (Table 9). These 

 data are consistent with other studies (1, 12, ^0, 4-1, 111, 135, 166), 

 and suggest that OM stability can be achieved by including vegetable 

 leg-omes in sequential cropping patterns. 



Soil nitrogen . Except for collard, fertilizer levels had no 

 significant influence on soil N measured as ^'W^^-N and N0-,-N (Fig. 6). 

 In cropping pattern HM-HM-HM, high soil N after collard was caused by 

 high levels of fertilizer. In addition, residual fertilizer from 



