Роль чистого пару в накопиченні води і відновленні водного балансу в сівозміні

Abstract

Встановлено, що в умовах північного Степу чистий пар, незалежно від попередників (ячмінь ярий, соняшник, кукурудза), способів обробітку ґрунту та особливостей догляду, на час сівби пшениці озимої забезпечує майже повне відновлення ресурсів ґрунтової вологи (151,7–180,7 мм). Навіть за відсутності дощів впродовж весняно-літньої вегетації рослин можна уникнути згубного впливу посухи на них і гарантовано одержати урожай зерна. Наявність чистого пару в короткоротаційній сівозміні зумовлює відновлення запасів продуктивної вологи чорнозему, особливо після польових культур, які пересушують 1,5-метровий шар ґрунту (соняшник). Ранній пар в Степу забезпечує збільшення коефіцієнта засвоєння опадів у кореневмісному шарі ґрунту (0–150 см) порівняно з оранкою і чизельним обробітком у середньому на 105–131 м 3 /га за рахунок рослинних решток попередника, які сприяють поступовому і рівномірному накопиченню снігу на полях In the conditions of the northern steppe due to fallow, irrespective of its predecessors (spring barley, sunflower, maize), soil cultivation methods and care features for winter wheat sowing, it is possible to achieve almost complete restoration of soil moisture resources (151,7–180,7 mm), which, even in the absence of rain during the spring-summer vegetation of the plants, guarantees a stable grain yield and prevents the harmful effects of drought.The presence of fallow in short crop rotation causes the restoration of productive soil humidity, especially after field crops that exceed the 1,5-meter layer of soil (sunflower). Early fallow in the steppe (after barley) formed a dense protective screen formed by stubble, crushed straw and dead vegetation during steady cooling. Within the undisturbed background, there was a significant decrease in wind speed in the surface air space, earlier, gradual and uniform accumulation of snow, increasing its viscosity and density. Combined with the high buffering and holding capacity of early fallow, this reduced water loss to runoff, evaporation, freezing and blowing, increased the sediment absorption coefficient and the additional moisture accumulation in the root layer of soil (0–150 cm), compared to tillage and chisel cultivation an average of 105–131 m3 /ha. Fallow lost more moisture in deep-loosened areas in autumn and less in variants of shallow disc tillage, which has explained by the formation of a compacted soil layer (10–20 cm) and a sufficiently high degree of projective coverage of its surface by plant residues. A shallow non-board soil tillage system had the advantage in grain and fallow crop rotation, where a bit more moisture (by 3,2 mm) had accumulated in the cold autumn-winter period than the board system, which has explained by the presence of mulch after cereals here and better moisture accumulation in early fallow. Regarding the other indicators, the same pattern has observed as in the grain-fallow-cutting rotation. Total moisture consumption during the growing season increased by 7,0 mm per board system compared to shallow (non-board). The water regime of the soil in the crop rotation with the field of sunflower was more intense than in the grain-fallow with the field of barley, as evidenced by lower moisture reserves before sowing crops – by 7,2–13,4 mm and higher total moisture costs – by 25,9–28,5 mm during the growing season. The water consumption here was also higher by 34,8–39,2 mm/t, which can be explained by the presence of sunflower in this crop rotation, which is able to use moisture from deep soil layers – more than 1,5 m. That is, the soil tillage systems had a smaller impact on forming a moisture balance than a set of crop rotations. The total soil moisture costs varied within a narrow range (306,2–310,4 mm) and remained almost unchanged depending on the tillage systems. It is necessary to note the more economical use of water by field crops under the shallow mulching system of soil tillage, as evidenced by the decrease of the index of water consumption by 13,4 mm/t to compare with board tillage.