155 



be diagnosed and both the yield and net profit increased 

 by suitable tillage. No hard and fast rules can be laid 

 down for other soil and other climatic conditions but a 

 few general principles that are of wide application may 

 be drawn from the work. In the discussion that fol- 

 lows some of these are pointed out. 



128. The Necessity for Plowing Grassy Stubble. The 

 average yield of wheat for five years on untilled grassy 

 stubble was 8 bus. 9 Ibs. less than on untilled stubble that 

 was free from grass. There are times when it may not 

 be best to plow clean stubble fields ; but there is never a 

 time or condition that makes it advisable to leave grassy 

 stubble unplowed. 



In 1914 grassy stubble surface cultivated in the fall, 

 produced 3 bus. 45 Ibs. less wheat and 13 bus. 5 Ibs. less 

 oats per acre than fall plowed land that was surface 

 cultivated; and spring plowing produced rather more 

 satisfactory results than fall plowing in that year. On 

 another piece of untilled grassy stubble the average yield 

 of wheat in 1914 was 5 bushels per acre. Adjoining land 

 in the same grassy condition was plowed shallow, double 

 disked, packed and harrowed in the fall of 1913 and as a 

 result yielded 13 bus. 30 Ibs. in 1914. 



It was observed that in all cases where grassy stubble 

 was plowed the yield was increased and the grass was 

 either totally killed or very much lessened. When the 

 same land was left unplowed, in many instances it be- 

 came overrun with native quack or, in low placess, with 

 sweet grass, and the cost of redeeming it was thus ma- 

 terially increased. 



Cereal crops cannot compete successsfully for moisture 

 and plant food with established perennial plants. 

 Neither burning nor surface cultivation will kill the 



