26 BULLETIN 1301, U. S. DEPARTMENT OF AGRICULTURE 
Observations on the individual trees show that mulching tended to 
increase winter resistance. The least winterkilling and injury were 
recorded on the mulched plats, and the greatest on those receiving 
clean cultivation, but the differences were not great where the apples 
were on hardy roots. The poorest survival of apples on hardy roots 
was in the manured plat. 
Good stands of plums still remain in this experiment, and good 
crops are being produced. ‘The effects of the different cultural treat- 
ments have not been marked; but, in general, trees in the mulched 
plats have been hardier than those of the same variety in other plats, 
and trees in the manured plats have suffered the greatest winter 
injury. ‘Trees in plats growing a cover crop have averaged slightly 
hardier than trees growing in clean-cultivated plats. 
The effects of the different cultural treatments on the yield and 
quality of fruit have not been marked. Manuring usually has 
resulted in a little better and larger fruit, but in slightly lower yields 
than other treatments. Mulching has given comparatively good 
yields and a good grade of fruit. There is but little difference in the 
results from clean cultivation and from a cover crop, but of late 
years there has been little difference in the treatments, as the cover 
crop has made small growth between the closely planted plums. 
over crops have been used in other plantings at the field station, 
and observations indicate that they were of value at times in checking 
soil blowing and in holding snow. ‘The results in most cases have 
not been very marked, and at present there are not enough experi- 
mental data to warrant recommendations. The evidence indicates 
that the desirability of growing a cover crop will depend largely on 
the season and the soil. 
SPACING OF FRUIT TREES AND PLANTING SYSTEMS 
Opinions vary as to what is the best spacing for fruit trees on the 
northern plains. Some advocate very wide spacing, because of the 
limited moisture. Others advocate close spacing in hedgerows or 
groups, for the sake of holding more snow and giving mutual pro- 
tection. There are not sufficient experimental data yet to justify 
recommendations. Most of the apples at the field station have been 
panies in the square or rectangular system, from 15 to 20 feet apart. 
lums generally have been planted from 12 to 15 feet apart. 
In one planting rows of tree fruits were spaced 16 feet apart, with 
the trees 4 to 6 feet in the row. Small fruits were planted between 
the rows of tree fruits, making the rows 8 feet apart. In another 
planting the rows were spaced 12 feet, with the trees 4 to 6 feet in 
the row. It is rather difficult to compare the results of these plant- 
ings with those obtained by regular spacing, owing to differences in 
the ages of the plantings, varieties, and soil. 
Better stands generally have been established, and the trees have 
suffered less winter injury during the first few years under the system 
of close planting, where more snow was held during the winter, and 
the trees received the benefit of mutual protection. Pears, apples of 
the Delicious variety, and a few sour cherries, in the close-planting 
demonstrations, suffered practically no injury in the winters of 
1920-21 and 1921-22. In former years such tender fruits were 
seriously damaged when planted by a system of wide spacing. But 
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