Unfavourable effect of cabbage cropping on the onion which follows

as an example of the deterioration of soil productivity in vegetable areas. (II)

Abstract

In the previous paper, it was recognized that the poor growth of onion which followed cabbage was always accompanied with the poor absorption of phosphorus which seemed to be due to the stronger acidity resulting mainly from the heavy application of ammonium sulfate for cabbage cropping,
In this report the authors describe the results of several investigations which have been executed to meet this situation as well as to ascertain our sup-position.
The results obtained can be summarized as follows.
1) To get enough yield of onion, basic application of a large amount of water soluble phosphorus (as superphosphate) was required overall in this area and it was especially so when it followed cabbage. For example, to get yield over 20 tons per acre, no more than 200 to 300 pounds of phosphorus per acre for the onion following barley and much more than 400 to 500 pounds of phosphorus per acre for the onion following cabbage was required respec-tively, while without phosphorus application almost no yield could be obtained in both cases. The differ-ence of onion yields due to the kind of preceding crop, therefore, was most pronounced when 100 to 200 pounds of phosphorus per acre was applied, which is the most common practice in this area.
To increase onion yield overall in this area and especially in the cases following cabbage, basic ap-plication of phosphorus as much as 500 pounds per acre was most effective and in addition controlling of soil acidity with lime or dolomite and application of increased potassium were also desirable in strongly acid soils.
2) A wide variation in onion yields was observed also in the area where onions had been grown suc-cessively year after year. The survey carried out in this area indicated that the yield of onion had the highest correlation with y₁ value of the soil and succeedingly high correlation with pH (H₂O), pH (KCl) and base saturation percentage in this order, while with 0.002N sulfuric acid extractable phos-phorus or exchangeable potassium no correlation could be found.
3) In the experiment field of our station onion was shown to be more sensitive to high soil acidity than cabbage. At soil reaction about pH 5. 2, the growth of onion was remarkably inferior to that of cabbage and at pH 4.2 almost no growth could be seen, while cabbage showed considerable growth 70 to 80% as much as at pH 6.2.
4) Among several properties of acid soil which influence on the plant growth, aluminum toxicity to which onion was thought to be especially sensitive and the influence of high concentrations of hydrogen ion were investigated by water culture method with onion and cabbage comparatively.
The data showed that at 1 ppm aluminum the growth of onion as well as of cabbage was inhibited equally and to high concentrations of hydrogen ion cabbage was more sensitive than onion, though more precise investigations are necessary for this kind of comparison.
5) Besides the poor growth of onion which fol I-owed cabbage, abnormal growth of cabbage itself had become to be seen especially in the area where cabbage had been grown successively.
Some of the distinctive features of this abnorma-ity, for example, the hooking and the development of thin and water soaked areas of light brown color around the margins of headed leaves and the dis-tortion, undulation and browning of tips of older leaves were quite similar to some of calcium defi-ciency symptoms induced in our laboratory by exclud-ing calcium supply in the middle stage of growth. In spite of this resemblance, however, there remains some possibility of boron or magnesium deficiency and much work should be done in order to evaluate this abnormality and further the possibility of its participation on the inferior growth of onion following cabbage.