Dear readers,

In this edition we are pleased to include papers presented at IPI’s special session entitled “Nitrogen and Potassium Interaction in Plant Nutrition”, held during the 5^th International Nitrogen Conference in Delhi (3-7 December 2010) and organized by the Indian Nitrogen Group (ING-SCON) and the International Nitrogen Initiative (INI).

Non-leguminous crop plants, take up nitrogen almost exclusively in two ionic forms (NH₄⁺ and NO₃^-). This uptake drives plant growth with dry matter N concentration ranging from 0.5-6 percent, a value only slightly lower than that of potassium at 0.8-8 percent. These N containing ions are derived from mineral fertilizers, mineralization of organic matter, and soil microbiological processes including nitrification. Additionally, with the rise of reactive nitrogen in the environment, some N inputs come directly from atmospheric deposition as well as indirectly from irrigation water.

Legumes fix atmospheric nitrogen contributing a significant amount of soil N, which benefits other crops when planted in mixed cropping systems. These multiple factors all make calculations of Nitrogen Use Efficiency (NUE) rather complex. Until it is possible through biotechnology to create a “super non-legume plant” which absorbs N from the atmosphere (will this ever be achieved?), management of the fertilization process clearly plays a key role in improving NUE. In this respect, potassium, via its role in the uptake and translocation of N and protein formation in the plant, deserves special attention.

The papers included in this edition from IPI’s special session relate to the improvement of NUE through N-K interaction. Brar et al. discuss this topic in cereals, with a sound agronomic approach; Cai et al. examine the physiological and molecular responses of rice to N, P, K and Mg deficiencies, and Bar Tal looks at NK interactions in the soil.

Finally, we look at the energy cost (in terms of GHG or CO₂ equiv. emissions) of potash production. The report shows that in comparison to other nutrients, the greenhouse gas (GHG) footprint of potash is relatively low. In times when energy costs and GHG are of major concern, this type of calculation provides a valuable extra tool to make the right decision for efficient nutrient management.

We trust this eclectic collection will prove interesting and informative, and wish you all an enjoyable read.

Hillel Magen
Director