EXPEEIMEXTAL STATIONS — TUENIP CEOP 1882. 375 



that the proportion of ash is greatest in those plots with full 

 manure, and least on those which are unmanured, or from which 

 some constituent has been withheld. Tarnips, like other plants, 

 take up more mineral matter than they require for their growth, 

 if an abundance of it is presented to their roots. The average 

 percentage of ash contained in the winter-manured section at 

 Pumpherston is greater than that in the summer-manured 

 section, and a comparison of the first ten plots (Table VIII.) 

 shows that peculiarity, and also shows that the proportion of 

 ash is greater when phosphates are applied in the dissolved 

 state. 



The ash over the whole station at Harelaw is not affected by 

 the difference in the time of application of the manures, but as 

 regards the phosphate plots the two stations show quite 

 concordant results. The increase of ash due to the dissolving of 

 the phosphates is quite as marked at the one station as at the 

 other, and this result confirms that obtained in former years. 



The percentage of ash does not rise and fall proportionately 

 with the amount of dry matter, nor yet wath the amount of crop 

 per acre, so that the total ash per acre cannot be determined 

 from these data. This is shown on Table IX., where the total 

 amount of ash per acre is shown in comparison with the total 

 dry matter. The amount of ash per acre gives an approxima- 

 tion to the amount of mineral matter removed from the soil by 

 the crop. It is only an approximation, for the mineral matter 

 in the plant suffers considerable change in the process of incinera- 

 tion, the organic salts are converted mostly into carbonates, while 

 small amounts of chlorides are volatilised and lost. But it is 

 sufficient for our purpose to consider the ash as a good measure 

 of the mineral matter lost to the soil by the crop. The average 

 ash on the two stations is given in the last line of the table. The 

 plots whose ash falls below the average mark are those deficient 

 in nitrogen, or whose nitrogen was supplied in an insoluble and 

 slow-acting form. It is the amount of nitrogenous manure of a 

 soluble kind in the manure or in the soil that determines the 

 amount of mineral matter in the crop. Plots 17 and 18 show this 

 very well. On plot 17 phosphate and potash salts have been 

 yearly applied, and yet the amount of mineral matter the crop 

 is able to take up is much smaller than that taken up by plot 18, 

 which has had nothing but nitrate of soda applied to it for fiv^e 

 years. The nitrate of soda has enabled the mineral matter in the 

 soil to be used by the crops, and the process would go on until 

 the available mineral matter in the soil was not suflicent to yield 

 half a crop. At present it has enabled the crop to grow well, 

 and extract mineral matter up to the tutal average of the 

 station. Plot 17 is being preserved for future use, while plot 18 

 is being exhausted ; but it is evident that the exhaustion is not 



