COMPARISON OF WET AND DRY SEASONS 59 



higher in the dry than in the wet year, averaging 61'2 Ib. 

 against 55'0 Ib. In the dry year the manures had compara- 

 tively little effect, the crops on all the plots being brought 

 nearer to a uniform level ; in the wet year, on the contrary, the 

 differences due to manuring were much accentuated. The 

 plot receiving farmyard manure occupies about its usual position 

 in the wet year ; but whereas it usually gives about the same 

 proportion of grain to straw as the medium nitrogen plots, in 

 1879 it was rather better than they were in this respect. In the 

 dry year this plot gives by far the heaviest yield of grain, almost 

 up to its usual average ; the straw also is much less reduced 

 than on the plots receiving artificial manures, due no doubt to 

 the water-retaining powers of the dung. It is interesting to find 

 that Plot 9, receiving nitrate and minerals, gave the best crop 

 both of grain and straw in the very wet year 1879, whereas in 

 the dry year, 1893, the crop on this plot fell below the crop of 

 Plot 6, which received the same amount of nitrogen as 

 ammonium-salts, though on the average of years the nitrate 

 answers better. This is contrary to the generally received 

 opinion that nitrate of soda is the more effective in dry, and 

 ammonium-salts in wet seasons. 



The very low crops on Plots 9ft and 10, which receive 

 nitrogen only, show that in a wet season the plant has very 

 little power of obtaining minerals from the reserves in the soil ; 

 and the great jump in crop produced by adding superphosphate 

 to the ammonia on Plot 11 shows that the phosphoric acid is 

 then more difficult to obtain. In a wet season when the 

 maturity of the plant is retarded, the ripening effect of 

 phosphoric acid will be exceptionally beneficial. In the dry 

 season the lowest returns come from Plots 10 and 11 (with- 

 out potash), and the potash on Plots 7 and 13 has an 

 exceptionally marked effect, showing that under conditions 

 of drought the plant specially responds to an abundance of 

 potash in the manure. Probably the explanation is that a 

 free supply of potash prolongs the growth of the plant, and 

 that in the absence of potash the ripening action of the 



