The paper discusses the influence of alternative fertilizes on the assimilative surface.

The process of products formation in the agroecosystem is very complex with its peculiarities, and anthropogenic as well as natural factors very closely and interdependently interlace in it.

The growth, development and productivity of fiber flax depend on the active formation of photosynthetic potential.

The given investigation proves that in the light gray forest soil the formation of the assimilative surface of plants substantially depends on anthropogenic factors, namely, on fertilization process.

The application of mineral fertilizers, plowing down of straw and green manure contributed to the increase of leaf surface area in the period of quick growth; the leaf surface index exceeded 1.5 times the control variant (without fertilizers) in the five-course rotation. The corresponding index in the four-course rotation was also 1 thousand square metres higher than in the control one.

The use of non-marketed output, winter wheat straw with post-harvesting sowing, green manure plowing down and the application of mineral fertilizers especially with the addition of mineral fertilizers for straw mineralization contributed to the intensification of photosynthesis processes, which is confirmed by the increase of CO PhAR (coefficient of performance, photosynthetic active radiation) index that according to years amounted to 1.08 – 1.21 – 1.38 percent in the five-course rotation and 1.06 – 1.1 – 1.2 percent in the four-course one. Thus, CO PhAR in the five-course rotation depending on weather conditions in the years of conducting investigations in condition of application of the above fertilizers increases by 0/02 – 0.1 – 0.18 percent respectively that contributed to the yield rise by 54 percent in the five-course rotation and 48 percent in the four-course one compared with the control variant.

During the investigation performance the variants with the combined application of fertilizers of organic and mineral origin showed the highest productivity - the compensation of active nitrogen substance per 1 ton together with green manure and moderate rates of mineral fertilizers, we obtained the increase of straw yield by 54.4 percent in the five-course rotation and 48.6 percent in the four-course one compared with the control variant.

The application of preceding crop by-products and green manure both separately and together with mineral fertilizers contributes to the development of the assimilation of fiber flax, increases the accumulation of organic mass and raises fiber flax productivity.

The clear increase of leaf surface was observed by the application of green manure and by-products both separately and together which exceeded the control variant to 0.3 units.

In the start of phase budding, leaf surface area slightly decreased compared to the period of quick growth – leaf surface index was in the range of 2.8 to 4.0 in the five-course rotation and 2.8-3.7 in the four-course respectively which is associated with withering away of lower layer of plant leaves.

It should be noted that the trend of increasing CO PhAR depending on alternative fertilizers manifested even in the extreme agroecological conditions, formed in 2007. These data show that the use of fertilizers in doses N₃₀P₄₀K₆₀, how in the five-course and in the four-course rotations positively influences on CP PhAR which constituted in accordance ,07 – 1,2 – 1,7 % and 0,78 – 0,82%.

Experience of domestic and foreign scholars shows the effectiveness of combined application of organic and mineral fertilizers. In the end, it is achieved improvements of the physical properties of soils, replenishment of stocks in the arable layer of humus and plant food elements, biological activity enhancement due to activation of microflora, which leads to increased productivity and crop quality. This is confirmed by to the results of our research.

Key wofds: fiber flax, fertilizers, rotation, assimilative surface, photosynthesis.