Saturday, 15 July 2006

Varietal Differences in Mineral Nutrition of Corn.

- Lykashov Aleksei Georgievic, Rostov State Univ, Dept of Soil Science and Agrichemistry, Bolshaya Sadovaya Street, 105 344006, Rostov-on-Don, Russia

We have used the Integrated System of On-line Diagnostics (ISOD) system as a basis to reveal the specifics in consumption of mineral nutrients by varieties with different duration of the vegetation period. We have identified the ability of each variety to form corn yield on the basis of its genetic potential. Development of each crop requires nutritional conditions different from the same for another crop due to its peculiar physiological and biochemical processes going on in its roots and overground organs. However, individual nutrition specifics is typical not only for different crops, but for their varieties, too. Corn makes no exception here. It is highly demanding as regards nutritional conditions and therefore creation of an optimal system for plant nutrition will provide for complete realization of the genetic potential of a variety and harvesting of maximum possible yield with specified quality. The research has been performed in field conditions. The soil is represented by calcareous black earth with humus contents in topsoil equal to 3,56%, pH 8,0, gross forms, in mg/kg, of nitrogen – 21, phosphorus – 75, potassium – 337. The area of land plots was 100 m2. Samples of soils and plants were tested using generally approved methods. Sampling time: 7-9-leaf stage (weight of tops, topsoil 0-20, 20-40 cm); milky-wax ripeness stage (the flag leaf, topsoil 0-20, 20-40 cm), dough stage (the flag leaf, corn ears), complete ripeness stage (corn ears). Nutrition balance was identified using the ISOD system (I.I. Yelnikov, 1987). Corn varieties and hybrides were: “Academia”, “Povolzhskiy 212 MV”, “Povolzhskiy 89 MV”, “Rostovsky 280”, “Donskaya vysokoroslaya”, “RM 992”, “RM 001”, and “Natasha”. Corn crop yield is determined by the following ratios of elements in plant tops (at 6-8-leaf stage): N/Cu, P/K, Ca/K, Mg/K, Sr/Ca, Sr/Mg, Cu/Mn, Cr/P, Cr/Mg, Cr/Sr, Cr/Cu, Zn/Mg, Zn/Mn, Zn/Cu, Ni/Cu (Table 1). Standard critical nutrition levels do not reveal varietal differences in the mineral nutrition of corn. However, its biological productivity (raw plant mass, plant height, weight of raw ears in leaves, weight of 1000 seeds, crop yield) is different with various genotypes. Processing of the data using the ISOD system results in subdivision of corn varieties into some groups that differ from each other in terms of nutrition balance and production indices. The first group is highly productive (“Natasha”, “RM 992”, “RM 001”). It is characterized by a higher index of nitrogen supply for the flag leaf (iN =1,2) and high index of manganese supply (iMn = 1,4-2,3). As we know, nitrogen is an element influencing organic substance production and control of vegetative mass growth and, consequently, the level of crop productivity (G.J. Rinkis, V.F. Nollendorf, 1982). We have also noted the influence of manganese over the ratio between corn ear length and kernel percentage, which in its turn directly influences corn yield. (Fig.1) The second group includes low yielders (“Rostovsky 280”, “Donskaya vysokoroslaya"). They are characterized by inadequate supply of nitrogen for the leaves and considerably higher index of supply with Zn, Fe, K, and P over that of nitrogen. The causes of that disbalance may be related to the environmental conditions or different abilities of corn varieties regarding assimilation of nutritional elements from soil and fertilizers. The higher agroecological variety potential is, the better is its nutrition balance already at the early stages of plant development. Apparently, testing of those varieties has been performed against agricultural background, which did not conform to the genetic requirements. That was the probable cause of their low productivity. In accordance with the collected data the best nutrition balance has been demonstrated by the “Povolzhskiy 89 MV” variety, which resulted in the maximum corn yield of 7,2 tons/hectare. Thus the ISOD allows identification of disbalance between elements and reveals variety specifics in mineral nutrition of plants at early stages.

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