24: • 



In this vineyard a gxYon quantity of fertilizer sppliod to the vxeakost grow- 

 ing vines procluccd about twice as many grapes as when applied to the strong- 

 eat grov/in^ vines. At 1928 prices, the value per acre of the increase in 

 grapo yield over the cost of fertilizer, averaged \|18 for the v^eakest grow- 

 ing vines compared v;ith $3 for the strongest grov/ing vinos • In this vineyard, 

 at 19S8 prices, it proV:bly paid to fertilize all virBS but it paid about 5 

 times bettor to fertilize the v/eakest vines than it did to fertilize the 



stronc^est vines 



f 



At 19B8 prices, the most profitable fertilizer application used on 

 the Barrett vinoyord v/as E18 pounds of sodium nitrate and 435 pounds of acid 

 phosphate. '%he value pet? aero of the increased yield over the cost of ferti- 

 lizer uas $15, compared v/ith flO when nitrate was used alone* The use of 

 nitrate of soda was slightly more profitable than the use of ammonium sul- 

 pha to« 



Of the 91 Michigrn intorvietirGd grovrers, only 8 applied any phosphoric 

 acid to their vingyards in 1928 and none of these applied as heavy an applica- 

 tion as v;as used in the tost on the Barrett vineyard • 



On the Barrett vineyard 218 pounds of sodium nitrate and S18 pounds of 

 muriate of potash gave increased yields about equal to tho nitrate-phOBphate 

 combination, v/hich was about nO percent greater than the gains in yield when 

 nitrate was applied alone. At 19E8 prices the nitrate potash combiiaation did 

 not pay as well as tho nitrate phosphate combination but paid better than 

 wheti nitrate was used alone* T/lion both phosphato and potash v/erc combined 

 with nitrate, tho yields nexo not increased over tho nitrate phosphate or 

 nitrate potash combinations • 



Cnly 6 of the 91 Michigan growers interviowod applied potash to their 

 vineyards in 1928» The grov/ers about paw Pav/, Lawton^ end Mattawan when 

 fortili$!!iin|5 vineyards, have generally applied sraai.l quantities of aianonium 

 sixLphata* According to the averages obtained for 1928, this method of 

 fertilization, on the average, has not greatly increased yields or profits* 



The Michigrn fertilizer plat tests, like those in Now York, ©mphnsize 

 h(m mttm^^XLtlY various vineyards respond to fertilizer explication^* In 

 isr. ^t*tri1,go'fe.' tests the incr eased yield due to fertilizer v/ns abdut 4 

 tiia^'U aji mioh on the Plaiixfiald soil type as on the Fox soils* Th^% 0mm0i^ 

 on tM Gdloma and Plainfield soils have had better results with f©r%il:Sri«^!NI: 

 thaft 0^'^mTB on the Fox and Bollofontaine soils may be indicated by 

 %c:% $$ j^drcent of the vino;^ards studied on the Coloma and Plainf ie; 

 rni^ «iif 43 percent of tho vineyards studied on tho Fox and Bollafom^ 

 miln 1t03^e fertilized in 19^8* When fertilizcxl, the Coioma and Plainj 

 irineyta^rds vrere fertilized heavier on the averngo than the Fox and Be: 

 irin^arMs* However, the differences in increased yield in 1928 bctwo^^^ 

 t^rtillzod and unfertilized vineysrrds were not so groat for vineyards om tfcf 

 Colmm ma Plainf iold soils as would be expected* 



Costs, by Areas 



Grape yields and production coGts for vineyards fertilized and for 

 those not fertilized in 1928, the year for vrhich this study \ms made, are 

 given in table 18. This comparison is not entirely satisfactory because only 

 a part of the increased yield derived from fertilizer was obtained in the year 

 the fertilizer was applied* 



