Experiments on the spacing of sugar beet: I. Results based on plot yields

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Since sugar beet was first introduced into this country many experiments have been conducted to determine the effects of spacing on yield: the general advice based on these experiments is that beet should be spaced as closely as working conditions permit. Davies (1931) carried out a series of experiments in the West Midlands, and came to the conclusion that yield was not related to the number of roots per acre, but was affected by their distribution. His work demonstrated that wide row distances could not be compensated by narrow spacing in the row. He found that yield increased as row distance decreased down to 16 in., but that singling distances of 4—10 in. produced no differences in yield of roots: the yield of green leaves, on the other hand, was increased as singling distance decreased, but was unaffected by row distance (Davies & Dudley, 1929). Although Davies' results would be generally accepted as a true expression of the general rule, many isolated spacing experiments fail to conform to them; it is possible that discrepancies in results, that undoubtedly occur, may be due to variations in the “plant” actually obtained in the experiments. Engledow et al. (1928), as a result of counts and weights taken on ordinary farm crops of sugar beet, concluded that uniformity of “plant” was a most important spacing factor affecting yield. In America Brewbaker & Deming (1935) have found yield to be related to percentage stand (correlation coefficients varying from +0·35 to +0·70), the regression between the two variables being approximately linear over the range studied. They also found that uniformity of “plant” was more important than spacing distances, either between or in the rows. Their work showed that single gaps had little effect on yield, because neighbouring beet compensated for them to the extent of 96·2%; serious loss of yield only occurred, therefore, with adjacent gaps. Pedersen (1933) studied the relationship between percentage of gaps and yield in a large number of Danish experiments with sugar beet and mangolds. In the case of sugar beet he found that the compensatory growth of neighbouring roots amounted to 76% for a single gap, and that the percentage compensation decreased as the size of gap (i.e. number of missing beet) increased. In an earlier paper (Pedersen, 1931) he had shown that under ordinary field conditions the distribution of gaps was approximately random.