52 



either labor, material, or fertilizer costs. For example, rates of 



return to labor were calculated as follows: 



Return to labor ($/$) = Gross return - Material cost 



Labor cost 



Similarly, return to material cash was calculated: 



Return to cash ($/$) = Gross return - Labor cost 



Material cost 



Production costs and market prices (46, 108, I50) were compared with 



5-year averages (I9) "to determine long-term profitability. 



Soil sampling and chemical analyses . Soils were sampled from 

 the top center of each bed to a depth of I5 cm. Samples, were oven-dried 

 at 70 C for 48 hours, screened to pass a 25-inesh sieve, and analyzed 

 for organic matter (OM) .content, total soluble salts (TSS) , pH, nitrate- 

 nitrogen (NO^-N), ammonium-nitrogen (NH, -N) , and K. Equal volumes of 

 soil and water were prepared as suspensions for determination of pH 

 and total soluble salts. Soil pH was measured using a combination pH 

 electrode. Total soluble salts were determined from soil solution 

 conductivity readings using a solubridge. Organic matter was analyzed 

 by the method of Walkley and Black as outlined by Allison (4). Nitrate 

 and ammonium were determined by steam distillation (18). Potassium was 

 analyzed at the Soil Testing Laboratory of Soil Science Department 

 using a double-acid extractant (I30). 



Statistical amalysis of data . Analyses of variance on marketable 

 yields and soil test results were run by computer using programs from 

 the Statistical Analysis System (11). Treatment means of marketable 

 yields and costs and returns from each crop were compsLred using Duncan's 



