Abstract

In order to investigate the effect of superabsorbents and mycorrhizal biofertilizers on water consumption and yield of field potatoes, a two-year experiment was conducted at the Hamedan Province Agricultural and Natural Resources Research and Education Center. In this experiment, the use of superabsorbents at a rate of 80 kg/ha, seed dressing of tubers with mycorrhizal biofertilizers, and combined use of superabsorbents and mycorrhizal biofertilizers with irrigation water at three levels of 75 and 50 percent of field potato water requirement were compared with no use of superabsorbents and mycorrhizal fungi as a control. The cultivar used was Agria 100. At harvest, total yield was measured and water use efficiency was determined. The results showed that under normal irrigation conditions (providing 100% of water requirement), the use of superabsorbent and mycorrhizal biofertilizer had no significant effect on the total yield of Refam Agria potato, but under low irrigation conditions, especially with 50% irrigation, the use of mycorrhizal biofertilizer and superabsorbent moisture material had a significant effect on growth and yield. In addition, under low irrigation conditions, the combined use of superabsorbent and mycorrhizal biofertilizer had a greater effect on growth, yield, and water use efficiency compared to their separate use. From an economic point of view, although the use of superabsorbent and mycorrhizal imposes a cost of about three million tomans on the farmer, under low irrigation and stress conditions, it increases the average yield by 5 to 6 tons of potato tubers (18% of yield) per hectare, which compensates for this cost well. In addition, with a 50% reduction in water consumption, approximately 2,000 cubic meters per hectare are actually saved in water consumption.

Problem statement

Superabsorbent materials are structurally networks of hydrophilic hydrocarbon polymeric materials. The water absorption coefficient of these materials is very high and they absorb more than 500 times their own weight in water (3) (Figure 1). Also, the water discharge in these materials is gradual and occurs gradually as the soil dries out. Therefore, the moisture of the soil and root environment remains at a suitable level for absorption for a long time without the need for re-irrigation, 4 and 5). Also, mycorrhizal fungi, which are used as biological fertilizers, increase the absorption of water and nutrients from the soil by using root-like organs called hyphae. In addition, they also produce growth hormones in a symbiotic relationship with the plant (8 and 10). The use of both of these substances increases soil moisture, and on the other hand, it helps the soil absorb water and nutrients, especially under conditions of drought and stress, through the roots of the apple tree.

Introducing the achievement or solution

Due to the limited rainfall in Hamedan Province (average annual rainfall of 313 mm), the inappropriate distribution and temporal dispersion of rainfall, and the high water requirement of the potato crop, it is inevitable to use agronomic methods to maintain and sustain the production and cultivation of potato crops in this province (6). In this regard, the use of moisture superabsorbents and inoculation with mycorrhizal biofertilizers are appropriate water management tools. These materials increase the competitive power of the potato crop by creating optimal growth and can lead to an increase in the quantity and quality of the crop by creating more optimal growth and avoiding stress during critical stages of growth (5 and 9). In this study, the moisture superabsorbent material was mixed in an amount of 80 kg/ha in the fertilizer tank of the seed tuber planter and distributed 3 to 5 cm above the tuber and in the planting furrows during planting. The tubers were also fertilized with biofertilizer, so that for each ton of seed tubers, one kilogram of planting medium mixed with symbiotic fungus was sprayed on the tubers in the potato tuber tank. The amount of irrigation water was adjusted to 75 and 50 percent of the potato water requirement, at three levels of 100, and was made available to the potato plant throughout the growth period. It should be noted that in this study, no chemical disinfection was used during the planting of seed tubers. The tuber yield per hectare was determined in the harvested product.

Promotional recommendation

The practical results of this experiment, which can be used and recommended in the field and on the farm level, were as follows:
1- Under normal irrigation conditions (providing 100% of the plant’s water requirement), the use of superabsorbent and mycorrhiza had no significant effect on the yield of potato (Figure 2).
2- The use of mycorrhiza biofertilizer and superabsorbent material under conditions of stress and lack of irrigation, and especially under severe stress (providing 50% of the plant’s water requirement), caused a significant increase in the yield of potato (Figures 4 and 5).
3- The combined and simultaneous use of mycorrhiza biofertilizer and superabsorbent material under conditions of stress and lack of irrigation had significantly better effects on increasing the yield compared to their separate use (Figures 4 and 5).
4- In total, under severe stress conditions, the yield of potato tubers with the combined use of superabsorbent material and mycorrhiza biofertilizer was about 18% higher. From the same amount of water and the lack of use of superabsorbent and biofertilizer (Figure 4
5- By calculating the economic benefits and losses of using superabsorbent and mycorrhizal biofertilizer, it is clear that the land-based apple farmer will incur about three million Tomans in costs by using these two substances. In contrast, by using superabsorbent and mycorrhizal in conditions of severe irrigation deficiency, there will be an average increase in production of 5 to 6 tons per hectare compared to not using them. If a price is also set for the water consumed, considering that in the current conditions the economic value of water in the land-based apple crop is estimated at about 27,000 Tomans per cubic meter, in practice, with severe irrigation deficiency and the use of superabsorbent and mycorrhizal biofertilizer, about 2,000 cubic meters of water will be saved. Therefore, a profit equivalent to 54 million Tomans per hectare will be received by the land-based apple farmer in return for the lack of irrigation. Most importantly, it can also hope for long-term and sustainable economics of field apple production. By summarizing the results of this research, it was found that the use of mycorrhiza and superabsorbent only under low irrigation conditions is able to stimulate growth and increase yield of field apple. Compared to mycorrhiza biofertilizer, the superabsorbent had a better effect on stimulating growth and yield and reducing the effects of stress under low irrigation conditions. In addition, under severe stress conditions, more favorable results were obtained by using them together.