July i, 1882.] 



THE TROPICAL AGRICULTURIST. 



85 



salts iu the soil lay in bands, and it was very eeldom 

 that they were equally distributed throughout. The 

 cause of the greatest quantity of nitric acid being found 

 in the second depth was very simple. The nitrates 

 were produced on the surface of the soil, and a few 

 weeks before these samples were taken there had 

 been a heavy fall of rain, which had washed them 

 down. They saw that the results whieli he had 

 meutiouei really gave them the reason why bare 

 allowing should be an operation calculated to so greatly 

 increase the fertility of the laud. In the early days 

 of the Rothameted e.xperiraents comparative trials were 

 mad', in adjoining fields, of wheat after wheat, and 

 wheat after fallow. The first ten years of those ex- 

 periments showed that the land that had borne an 

 alternate crop each year after fallow had produced as 

 much wheat iu its five crops as the land that had 

 grown wheat continuously had produced in its ten 

 crops. They would understautl how that happened 

 when they observed the amount of nitrates found to 

 be present in bare fallow ; when the wheat followed 

 a year's fallowing, it 'found two years' nirates to feed 

 upou. Of course the advant ige or disadvantage of bare 

 fallowing depended almost entirely on the weather, 

 for iu wet weather the advantage was to a grent ex- 

 tent lost, owing to the nitrates being wasiied away, 

 and removed in the drainage water. It was therefore 

 a dry winter climate which made bare fallowing of 

 value. He would next speak of the intlueuce of a 

 crop on nitrification. It was two-fold. First of all, 

 they could not grow any crop on the laud without 

 diminishing the amount of drainage. The amount of 

 evaporation from a Held under crop is very much 

 greater than from a field under f.illow, and therefore 

 the soil necessarily suffered less from drainage. The 

 other eflfect was that the crop was eager to ol)tain 

 nitrates, and therefore the tiitrates were taken up 

 by the roots, and turned into msoUible organic matter. 

 He would lay before them the results of some determ- 

 inations of the araoaut of nitrates present in cropped 

 and fallow land. In 1878 they had at Kothamsted a 

 field half in fallow and half in beans. After the 

 removal of the crop of beans, samples were taken 

 from that land, and also from the laud under bare 

 fallow. The first IS inches of the soil that had been 

 bare fallow contained 3U lb. of nxtrog'iu per acre, and 

 that from which the beans had been taken only con- 

 tiined 10 5 lb. per acre. At the same time a similar 

 experiment was tried with land nnder fallow and land 

 under wheat. The land under fallow yielded .33 '7 lb. 

 of nitrogen per acre, and that on which wheat had 

 been grown only 2 '6 lb. per acre. That was a strik- 

 ing instance of the extremely perfect manner in which 

 the removal of the nitrates from the soil was carried 

 out by the wheat crop. The drainago water from 

 several plots of the experimental wbeat field contained 

 in the summer time no nitric acul at all, as it was taken 

 up so completely by the wheat crop. They had now 

 arrived at three cardinal points as regarded nitrates t 

 (1) they were being continually produced, (2) tliey 

 were very easily lost, and (3) that th.at loss can be pre- 

 vented by a crop. This subject became one of very 

 great .agricultural importance when thev saw the con- 

 siderable money value of nitrates. Taking the prer-ent 

 price of nitrates in the market, the loss by drainage 

 of 44 lb. of nitrates per acre represented a loss of 

 379. per acre per annum. That was a great loss, and 

 it followed that economical farming depended very 

 much indeed on the economising of the nitrates. Now, 

 taking the various systems of cultivation, bare fallow 

 involved the greatest risk of loss of nitrates, corn crops 

 involved the next greatest, roots came next as causing 

 a less loss, and lastly, pasture involved the least 

 possible loss of nitrates. Why was this? They had 

 seen that in bare fallow the loss was caused by the 

 facility which the absence of crop gave for having the 



nitrates washed away. As to corn crops, their growing 

 period was practically limited to three months, April 

 May, and June, but the process of nitrification in the 

 soil would go on in July, August, and September with 

 vigour, and the nitrates then produced were freely 

 lost in winter, when there was abundant drainage 

 and no crop to feed npon ihem. If wheat was grown 

 after wheat, there might be a considerable loss of 

 nitrogen from the soil, from the fact that loss by 

 drainage went on during a great part of the season 

 when the production of nitrates was most active, and 

 when there was no growing crop to retain them. 

 When tliey came to the root crop, they had growth 

 goiug on in June, July, August, September, October, 

 and up to November, during the very period of the 

 year wheu they most wanted to save the nitrates. 

 Mr. Lavves deserved the credit of first pointm" out 



that the roots iu a rotation were a conservative c'rop 



they saved the nitrates in the soil ; when they were 

 fed off on the land, the roots return-d to the soil the 

 nitrogen tiiey had saved. In pasture they had the 

 best possible conditions for saving the nitrates for 

 there they had vegetation on the land all the year 

 round— they had the largest amount of evaporation 

 and the smallest amount of drainage. Was it then 

 possible to do anything to diminish the loss of nitrates? 

 He believed that a part of the present agricultural 

 depression was owing to the extremely wet winters 

 of the past few years, which had resulted in lowering 

 the ondition of the soil by washing out extraordinary 

 amounts of nitrates. Could anytliing be done to alter 

 this ? He was not a practical farmer, and he wished 

 them to take anything he said on that part of the 

 matter as subject to a much better opinion than his own. 

 But he would point out a tew things that might 

 possibly be a help. For instance, in the case ol a 

 bare fallow, the good work on the fallow was done in 

 the summer time — that tvas when they got the ad- 

 vantage of the fallow ; and the evil came in the winter. 

 A gentleman had told him that he had foun d it a 

 good plan to get the fallows clean in July, to then 

 plant mustard or rape, and then, before sowing the 

 wheat in the autumn, to plough the mustard or rape 

 (which ha 1 grown vigorously) into the land, and then 

 to sow t le wheat. Now that gentleman knew nothing 

 at all about nitrates, but he hail done just what he 

 ought to have done it' he desired to save them. The 

 mustard or rape took up the nitrates, and turned them 

 into insoluble organic matter, and wheu it was 

 ploughed into the land, it slowly resumed the form of 

 nitr.ates, for the nourishment of the wheat plant. 

 But for that simple plan, a great part of the nitrates 

 produced in summer might have been lost by the 

 drainage of the winter months. Again, he thou"ht 

 there was no doubt — though he was aware that there 

 was a great practical dilficulty about this point — that 

 it was not advisable to plough light land in the 

 autumn. By ploughiig land in the an umn they did 

 their best to give vigour to the production of nitrates. 

 They were also d-stroying the weeds, and in the 

 winter the weeds were the farmer's friends, for they 

 prevented drainage to some extent, and also helped 

 by taking up the nitrates ; and thus, if the farmer 

 left the destruction of the weeds till spring, they 

 were more or less equivalent to a green manuring. 

 He would therefore recommend that ni more plon-'h. 

 iui; be done in the autumn on light laud than was 

 ahsolutely necessary. Having pointed out the v.ilue 

 of long rooted crops, such as rape, mangold, clover, 

 and sainfoin, which helped to bring up again nitrates 

 that had washed down to a considerable depth, and 

 thus muke them valuable for plant food, he passed on 

 to say a few words on iii*-rification in relation to 

 manures. Experiments h;id -hown, from observations 

 made on the drainage watei from a field in which 

 ammonium salts had been aji|jlied to the wheat crop, 



