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Climate change and drought stress

WHAT CAN WE DO IN FERTILIZATION?

The impacts of climate change are noticeable for everyone. Temperatures – especially in the last years – are increasing and getting more extreme, and rainfall is becoming more and more unpredictable. All these changes mean new challenges for the agriculture.


Cultivated plants require adequate amounts of water, light, air and mineral nutrients to maximize their full productive potential. The plants take up most of the nitrogen, phosphorus, potassium, calcium, sulphur and trace elements from the soil, if there is enough moisture. All nutrients are important, but because of its physiological role, potassium (K) is the most valuable nutrient from the point of drought stress.


Potassium – as a macroelement – is needed and used in high amounts by the plants, despite, potash fertilization is many times neglected. The proper K concentration is essential in the cells to maintain the right osmotic pressure, and so it has an extreme important role in the closing and opening of the stomatas. If the plants have a low potassium supply, the functioning of the stomatas is disturbed, therefore the water loss due to transpiration wil be much higher. Potassium increases the water usage efficiency of the plants, meaning the plants will need less water for the production of one unit of dry matter. Apart from this important function, K has an impact on the transportation of the carbohydrates, therefore it influences the sugar content of the cells, which is important in the frost tolerance. Last but not least, potassium is also needed for the activation of many enzymes.


Numerous experiments have shown that a sufficient supply of potassium facilitates photosynthesis even in the case of servere drought stress, while photosynthesis stops almost completely in plants poorly supplied with potassium (Figure 1).



OPTIMAL NUTRIENT SUPPLY - HIGH YIELD


Optimal plant nutrition – apart from the importance of potassium – is essential to increase the stress tolerance of plants and to obtain good yields. Plants cultivated on soils with good nutrient supplying ability can tolerate drought much better. Therefore, especially in the case of maize – whose vegetation period is mostly in summer – a basic fertilization with NPK fertilizers is essential. This is clearly highlighted in the results of 7 field trials conducted by Borealis L.A.T at different locations in Central and Eastern Europe, under different climatic conditions (Fig.2).

NITROGEN HAS TO BE UTILIZED


Another important topic – related to the global warming – is the choosing of the right nitrogen form. In a warm spring weather it matters, how much of the applied nitrogen will be used by the plants and how much will be lost in the form of ammonia to the air. Better nitrogen use efficiency results in higher yields, of course. This – beside of the importance of NPKs – was also proven in our Hungarian maize field trials (Fig.3). The application of NAC 27 N (CAN) resulted on both N levels in higher yields, as the application of UREA 46 N. Application of nitrogen in the form of nitrate is much more effective, as its gaseous ammonia losses – which can be up to 13% in the case of urea – are much less.


CONCLUSION:
Basic fertilization with NPKs and the maintanance of the good K level of the soils is a must. Especially in the case of maize it is worth to use high quality NPK fertilizers, such as COMPLEX 15/15/15 +7SO3+Zn, and COMPLEX 14/10/20 +10SO3. To avoid the temporary P deficiency, we recommend COMPLEX 20/20 +7SO3+Zn as a starter application. Nitrate containing nitrogen fertilizers are more effective and environmentally friendly. Just plants with optimum nutrient supply can survive the disadvantageous weather conditions without high yield losses.