21. 



In Michigan^ the fertilized vineyards yielded on the .average about 

 one fourth of a ton more per acre than did those that were not fertilized 

 or that were fertilized very little* The increased yield averaged about the 

 same for the vineyards on the sandy soils' -about Lawton and Mattawan as for 

 the vineyards on the Pox sandy loam, soil west of .Paw Paw« The return per 

 hour of man labor averaged more for -the fertilized vineyards that for those 

 not fertilized. 



Fertilizer tests by Dr» Partridge on Michigan" vineyards in which 

 nitrogen was applied in different quant itie-s and in combination with phosphor- 

 ous and potassium on a very productive. vineyard on ..the P ok .sandy loam soil 

 are given in table 15» On the average' the vine:/ards on the fertilized plats 

 yielded at the rate o*f •SG of' a ton more per acre than the unfertilized plats# 

 At 1928 prices, the value of -the Increased yield exceeded the ccst of the 

 fertilizer in only 1 of the S- tcs't plats*. The largest losses v/ere on plats 

 fertilized the heaviest. The plat not fe-rtilizcd yielded at the rate of 

 o^evk tons of- grapes per acre in 1922, 1923^ and I92U. It 192S prices, 

 fertilizers did not pay on such a vigorous and productive vineyard. 



• Another experiment was reported by Partridge and Veatch on the Barrett 

 vineyard situated largely on a Plainficld loamy sand soil, (table I5.) The 

 check plats on this vineyard from I92U to 1929 yielded at the rate of 2.26 tons 

 per acre. The yields for 3 of the 6 fertilized plats exceeded the check yields 

 by more than 1 ton per acre. • At 192S prices, the value of the increased yield 

 exceeded the cost of the fertilizer 'for each of the trials. For 3 of the 6 

 fertilized plats there was a gain above the cost of fertilizer when nitrate 

 was used alone or in combination with phosphorous or potassiiom of from $12 to 

 $13 per acrei> This test indicates that fertilizers are very profitably applied 

 to vineyards like the Barrett vineyard. • 



Erosion in vineyards in Michigan -is much more serious than in New York 

 and Pennsylvania. Although the Barrett vineyard is relatively level, the 

 authors ^tate that there has been considerable loss of soil by surface washing 

 since the vines were planted. According to the operator the soil is "going 

 down" and a certain amount of root pruning is inevitable each year. The 

 bomus or organic matter in the surfacfe soils was indicated by the depth of 

 the humus layer. On the 4-acre block used for the fertilizer test the depth 

 of the humus layer of the surface soil varied from loss than 3 inches to over 

 9 inches. It is interesting to ncte how important those variations in the 

 depth of the surface soil were in determining yields in this vineyard, (table 

 lo.) The a\ithors arrive at the conclusion that production is 'enhanced as much 

 by planting vines on soils with hunus layers 3 01* ^ inches thick as it is by 

 iieavy annual applications of inorganic fertilizers made at large expense. 

 These data suggest the importance of setting Vineyards on deep soil and of 

 preventing the washing away of this soil. 



The vines in the Barrett vineyard were classified according to their 

 initial vigor as measured by the pounds of wood trimmed per vine in 1923* 

 The weak-gro\Ying vines were usually on soils of a thin humus layerj the vigor 

 of vine growth v/as closely associated with thickness of the hiimus layers 



At the beginning of this experiment in 1923 ^ One half pound ox* lo^s 

 p^v Vine^ of 1- and 2-^year old wood was removed from I5I vines and 1.6 pounds 

 tod more per vine from 75 vines. The increase in yield from 192^ t6 1929 

 fe^Veraged I.32 tons per acre for the I5I vines on the fertillzod plats^ compared 

 With 463 ton per acre for the 75 vines on the unfertilized platj?* (table I7.) 



