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  • Author or Editor: Max W. Hammond x
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Abstract

Soil temperatures around roots of apple (Malus domestica Borkh.), peach (Prunus persica (L.) Batsch), and cherry (Prunus avium L.), were modified during anthesis. Cool (1.5 – 9°C) and cold (1 – 4.5°) soil temperatures in the field were achieved with white plastic covers over insulation over snow, and with coolant coils in the soil covered with insulation and clear plastic. Warm (5 – 19°) and hot (18 – 26°) soil temperatures were achieved with clear and black plastic covers over bare soil and with buried heat tapes under insulation and clear plastic. Potted peach seedlings were subjected to freezing (−3°) and warm (18°) soil temperatures in a growth chamber. No advance or delay of anthesis resulted from any of the treatments except delay in frozen soil.

Open Access

Abstract

A controlled environment study was conducted to determine if ‘Russet Burbank’ potatoes (Solanum tuberosum L.) were more tolerant of NH4-N as established plants than as young plants. When grown on one N source for 86 days, root and shoot growth were best with NO3-N, intermediate with NH4 + NO3, and least with NH4-N. Changing the N source from NO3-N or NH4 + NO3 to NH4-N at tuber initiation (58 days after planting) reduced both shoot and root growth. Conversely, changing the N source from NH4-N to NH4 + NO3 improved growth. The highest tuber weights were obtained with continuous NH4 + NO3 or when NH4-N was applied at tuber initiation to plants previously grown on NO3-N alone. Nitrogen source also influenced absorption of other nutrients. Changing the N source once plants were established, however, did not have a consistent effect on mineral composition. We conclude that when NH4-N is the sole form of N available to the plant, it is detrimental to potato growth regardless of stage of development.

Open Access