鉀肥形態對於鳳梨生產之影響

EFFECT OF DIFFERENCE IN THE FORM OF POTASH ON PINEAFPLE

筆者曾於民國認43至44年就本場42年種植區土壤肥力及鳳梨產量加以調查分析，發現土壤有效態鉀素含量之多寡，不但對於果實產量有顯著影響，而且與肉聲果（即組織微密而果肉黃色濃度之優良果）生產率有明顯之正相關關係（2）。繼之，在43年種植區進行氯化鉀適量試驗（3）及三要素適量試驗（7），證明氯化鉀之施用，在缺鉀土壤上，有極顯著之增產效果，惟氯化鉀之多量增施在氮肥不足情形下，能引起肉聲果產率之降低，而氮肥充足時，雖氯化鉀少施稍能增加肉聲果數，但多量增施時仍未見肉聲果之繼續增加。由於土壤鉀素與氯化鉀兩者，對於肉聲果產率之影響有異，故氯化鉀所含氦素之作用，需要進一步檢討。

1.Two forms of potash were compared as to their effects on the plant crop of pineapple. The treatments were : (1) Check: 3g K2O per plant, applied in the 1st dressing. (2) KC 1: 12g K20 per plant applied in addition to the check in the subsequent applications in the form of potassium chloride. (3) K2S04 : same amount of K20 as in (2),but using potassium sulfate. N and P205 applied were 15 g and 3 g, respectively. 2.Though no significant difference in growth was obtained. the summer fruitage for KCI plots was only 92%, being significantly lower than those of check find K2SO, plots (both 97%) The lowering of fruitage is attributable to the chloride effect and has no bearing on potassium itself. 3.The mean fruit weight is biggest for K2SO4, plots and smallest for the check. The yield increment over the check was 2.7 tons per Chia (slightly lass than a hectare) for the K2S04 plots (5.3% increase) , while KCI gave lower yield than the check, though not significantly; it is to be noted that the soil had been in follow for 3 1/2 years, and was mulched all over with rice straw, and therefore, was rich in available potassium. 4.The fruit maturity was earlier for K2S04 plots, presumably because of the earlier maturity of plants which had favored the inducement of floral initiation by low temperature. The mean date of fruit maturity and the date of maturity peak were the same for the check and KCI plots, though for K2S04 plots, the mean date of fruit maturity was 4 days earlier, and peak was 6 days earlier. The numbers of days between the peaks of maturity and the corresponding flowerinducing low temperature valleys were 203-204 days in all treatments. 5.The number of sucker-bearing plants was less for the KCI plots than for check and K2SO4 plots, although the difference was not significant statistically ; this means there is no possibility of producing a higher yield in KCl plots in the ratoon crop to cover the loss in plant crop yield. 6.K2S04 produced greatest proportion of the 'flesh-sound' fruits, which are characterized by their compactness of texture, low sponge content, and intense coloration of fiesh, while KCl produced the least proportion of them, and the check came intermediate. Both KCI and K2S04 increased the juice acidity and sugar content over the check. The acidity of KCl fruit was slightly higher than that of K2SO4 fruits. 7.Neglecting the value of differ-ence in fruit quality. the net profit obtained at harvest was much higher for K2S04 treatment than for the KCl treatment, the latter having resulted in considerable net loss. 8.According to the leaf analysis conducted at the stage of floral. initiation, the KCl and K2S04 plants contained greateramount of tissue potassium than the check plants. The nitrate concentration was the highest in K2SO. plants, and the lowest in KCI plants ; this indicates that the potassium ions enhanced the uptake of nitrate, while the chloride ions depressed the uptake of nitrate. The chlorine content of tissue was twice as higher for KCl plants as for the check and K2S04 plants. n.The authors present a hypothetical view in a diagram for generahzing the relation of soil potassium status and plant response to added potash as affected by the two forms of potash salt.