Voc. XIV. So. 343. 



THE ACKUTLTURAL NEWS 



199 



PRODUCTION OF AMMONIA AND 

 NITRATES IN HAWAIIAN SOILS. 

 Bulletin No. -'IT of the Hawaii Agricultural 

 Experiment Station contains the following summary oi 

 the results obtained from an investigation into the 

 occurrence of ammonification and nitrification in the 

 soils of thai t< rritory:— 



(1) The pasture and forest lands ol Hawaii, the soils 

 osed for aquatic crops, and most other island soils not 

 subjected to frequent tillage :ontain very small amounts oi 

 nitrate but considerably larger amounts of ammonia. 



(2) The uncultivated soils.are capable of supporting 

 vigorous ammonification ol dried blood, but are toxic to 

 nitrification. 



(:!) Nitrification lakes place in Hawaiian soils after 

 aerated conditions have been maintained for a period of 

 several months, but not immediately following tillage. 

 Ammonification is also stimulated by tillage. 



(I) The inactive state of nitrification in the unculti- 

 vated .-.nils is not due to the absent^ of the nitrifying 

 organisms or aciditj 



(5) Sterilization in the autoclave and burning tailed 

 tp bring about conditions favourable to nitrification, but 

 burning caused a splitting off of large amounts of ammonia. 



hi The beneficial effects to crops produced by burning 

 refuse is probably due in considerable part to the formation 

 of ammonia. 



(7 The plants growing on the uncultivated soils 

 probablj absorb nitrogen largely in the form of ammonium 

 compounds. 



(8) Partial sterilization of Hawaiian soils stimulates 

 ammonification for a short time, usually about two weeks, 

 followed then b) a retardation in ammonification. Nitrifica- 

 tion is inhibited temporarily by partial sterilization, but 

 later on regains its activity, due possibly to reinoculation 

 with iii boii rganisms. 



(9) Reinoculation of the partially sterilized with 

 untreated soil did not overcome the stimulation to aiumoni- 

 fication, but stimulated nitrification. 



(10) A permanent increase in the available nitrogen 



(nitrate and ammonia) was effected by partial .sterilization in 

 Certain soils, while in others the effects were very temporary. 

 In the latter instances it is possible that nitrate and ammonia 

 Consuming organisms gained the ascendancy toward the close 

 of the experimental periods, and that ammonification was 

 partially inhibited by the too great accumulation of the 

 products of bacterial action. 



(II) Two tenths per cent, of toluol ami carbon 

 bisulphid were equally as effective as t per cent. 



(12) It is believed that both the aeration and partial 

 sterilization of Hawaiian soils brteg about stimulation in 

 bacterial action through effects produced on the colloidal -oil 

 films, but continued aeration in the more effective. The 



protozoan tlieorj appears to be "i doubtful application to 

 soils. 



(13) Calcium carbonate produced considerable stimula 

 in the ammonification of dried blood ami soybean cake 



meal in certain soils; in others, only slight effect.-. Magnesium 



carbonate, on the other hand, produced marked stimulation 



in a number of instances: In two soils only, magnesium 



. it. was toxic to ammoaification. Dolomitic and 



calcareous limestones produced effects similai to those 

 produced by calciun i ite. 



(II) In certain soils calcium carbonate stimulated 

 nitrification, while in others no effects wen 



Magnesium carbonate, on tl ther hand, was tpa 



nitrification in a majority "i the -oil- studied 



(15) Nitrification was found to 1 pially as active in 



the manganiferous and titaniferous -oil- as in the other soils 

 studied, but magnesium carbonate was especial!} toxic in 

 these soils, and was nine toxic to the nitrification oi soj bean 

 cake meal than ■■( dried blood. 



ihi) Dolomitic ami calcareous limestones produced 

 similar effects on nitrification, bringing about stimulation in 



the soils in which calcium carbonate | luced stimulation 



and no effects in the soils that wen unaffected by calcium 

 carbonate. 



(17) The application of calcareous and dolomitic 

 limestones will probably produce similar effects on the 

 availability of nitrogen in Hawaiian soils, but regarding the 

 effects of the burnt lime., further experiments are necessary 

 before conclusions can be drawn. 



(18) Positive conclusion can not be drawn concerning tha 

 effects of the lime-magnesia ratio on ammonification ami nitrifi- 

 cation in soils. The evidence to date, however, points to the 

 probability that this ratio exert.- very little, if any, influi 

 bacterial action in the usual soil. The concentration of 

 magnesium salts in the soil moisture, on the other hand, 

 probably has an important influence on bacterial action. 



(19) The experiments recorded in this bulletin empha- 

 size the importance of maintaining the best aeration possible. 

 This can not be done profitably without the rotation of crops, 

 including green manuring. The exceedingly high clay content 

 of much of the cultivated land- causes the soil to "be very 

 heavy, and to pack after rains, so that aeration becomes poor. 

 By increasing the humus content aeration will be increased, 

 drainage facilitated, and bacterial action stimulated. Thus, 

 the plant food will become more available, deeper rooting of 

 crops be encouraged, and their ability to withstand the 

 effects of drought be greatly increased. Xo system of soil 

 management in Hawaii can be judicious or permanent without 

 the rotation of crops and the maintenance of humus. 



The storage and application of pen manure has been 

 studied recently in Germany with interesting results. The 

 main conclusion drawn is. thai to obtain the maximum 

 benefit, the solid and liquid excreta should, on the estate, be 

 utilized separately. The reasons for this are so obvious that 

 one is surprised that they have not been pointed out earlier. 

 Firstly, the two manures are essentially different in their 

 effects: for example, the nitrogen in urine acts as rapidly as 

 that in sulphate of ammonia, whereas the solid excreta's 

 effect is very much slower. The value of the -olid 

 matter depends largely upon its high bacterial content, 

 and its richness in humus-forming organic substances. 

 Urine, on the other hand, is relatively pom in bacteria and 

 humus-forming substances, but as already pointed out. rich 

 in quickly available plant nutrients. It is suggested that 

 urine should be more commonly applied to the soil along 

 with absorbents, like peat moss. Further information 

 on this subject may be obtained from the ref 

 the English Journal of the Boftrd of Agriculture, for 

 May 1915. 



