Changes of Nitrogen, Phosphorus and Potassium Contents in Potato Plants
During the whole growth period, the nitrogen content in leaves is the highest, the tuber is the lowest and the stem is in the middle. The potassium content is the highest in the stem at the early growth stage, the middle in the leaf, the lowest in the tuber and the highest in the tuber at maturity. The change of phosphorus content is complicated and often changes with different growth periods. The phosphorus content is about110 of nitrogen, and the difference between organs is also small. The phosphorus content of each organ is stem and leaf tuber before tuber formation, and leaf tuber stem after tuber growth period.
With the development of potato, the distribution of nitrogen, phosphorus and potassium in different organs is also different.
Distribution of nitrogen, phosphorus and potassium in different organs at different growth stages (%)
At the seedling stage, all kinds of nutrients are supplied to the stems and leaves (only the aboveground parts are considered here), in which nitrogen and phosphorus are mainly distributed in the leaves and potassium is mainly distributed in the stems. After tuber formation, the proportion of nutrients distributed to stems and leaves gradually decreased and gradually increased in tubers. This reflects the high consistency between plant nutrition center and growth center. At maturity, most nutrients have been transferred to tubers, which become the metabolic center and "base camp" of nitrogen, phosphorus and potassium. According to Harris( 1978), when the nutrient accumulation is maximum, the nitrogen, phosphorus and potassium accumulated in the tuber can account for 77%, 89% and 79% of the total absorption of the whole plant respectively.
With the transfer of growth center from stem and leaf to tuber, the content and distribution of nitrogen, phosphorus and potassium in potato also move accordingly. The equilibrium period of nutritional content can be regarded as a sign of the transfer of nutritional center. The transfer rates of nitrogen, phosphorus and potassium in stems and leaves are 565, 438+0%, 54% and 44% respectively, and the transfer rates of nitrogen, phosphorus and potassium in mature stage are 67%, 77% and 74% respectively.
According to the research of Osaki Kazuo (1987), the speed of absorption and accumulation of nitrogen, phosphorus and potassium is faster than that of dry matter except phosphorus. Calcium varies with the growth status, and the distribution ratio to tubers is small, mainly in stems and leaves, and it decreases sharply with the decrease of dry matter weight everywhere. Magnesium is similar to calcium, but its distribution in tubers is larger than that of calcium. The distribution of zinc content in potato is stem and leaf. The zinc-rich range of tuber can reach 25.5 ~ 102.9 mg/kg (dry weight); The content of zinc in stems is high at the initial flowering stage and low at the harvest stage; There was little change in leaves during the two periods (Kang Yulin, 1992).