Table 2.— Average production of grass in experimental plots, by treatment, at Blackbird mine, 1974 and 1979 



Production 



Treatment 1 Plots treated 1974 1979 







Lb/acre 



Kg/ha 



Lb/acre 



Kg/ha 



TH-NA 



1, 2, 2 12, 20 



323 



362 



372 



417 



TH-A 



3, 16, 23, 2 24 



486 



544 



246 



276 



SH-NA 



2 6, 9, 17, 22 



337 



377 



340 



381 



SH-A 



4, 5, 8, 13 



645 



722 



371 



416 



SP-NA 



7, 10, 15, 2 18 



661 



740 



441 



494 



SP-A 



11, 14, 19, 21 



674 



755 



469 



525 



Treatment code: 



SP, seeded by seeder-packer, followed by application ot mulch and treatments; 



SH, hydroseeded, followed by hydromulching and fertilizing; 



TH, seed, mulch, and fertilizer all applied by hydromulcher in one operation; 



A, amendment by addition of hay; 



NA, no amendment. 



2 



Study site extended into a salt-affected area which influenced results. Those plots were not included in calculations. 



Species 



Just as total production was less in 1979 than in 1974, 

 so was the number of grass species in the stands. In 

 1979, the dominant species were timothy, orchardgrass, 

 and smooth brome — all introduced species. Other 

 grasses that survived the 6-year period were the 

 intermediate wheatgrasses and Great Basin wildrye, a 

 native. In 1979, we found that hairgrass (Deschampsia 

 caespitosa) had invaded the study site, especially in 

 areas where some of the planted grasses had declined 

 because of reacidification. 



The data on both grass production and persistence of 

 species lead to the following conclusions: 



• Seeding by the seeder-packer gave higher grass 

 yields, both first year and long term, than either 

 method of hydroseeding. 



• On areas too steep for the seeder-packer, the 

 two-step hydroseeding and mulching system 

 gave higher grass yield results than the standard 

 one-step hydroseeding technique. 



• Although plots planted by the standard one-step 

 system produced less, stands generally are 

 acceptable in terms of ground cover protection 

 and, at the same time, encourage natural 

 succession. 



• Use of alfalfa hay as a soil amendment produced 

 higher yields of grass in 1974 at the 95 percent 

 statistical level, but this benefit was not so evident 

 after 6 years. 



• The rotary tiller is not a satisfactory implement for 

 mixing organic mulch into the rocky mine spoils 

 found on this mine because: 



1. The rotary tiller crushes rocks and 

 increases the reactive fraction of the spoil. The 

 tiller can overpulverize the spoils, destroying 

 texture and decreasing infiltration. 



2. The rotary tiller uses more energy per 

 cubic foot of soil moved than any other tillage in- 

 strument and more than three times that used 

 by the moldboard plow (Buckingham 1976). 

 Rocks dull the blades, and hay that is not cut by 

 the dull blades is ineffective. The machine is 

 soon destroyed. 



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