EVALUATION OF NUTRIENT STOCKS AND SOME SOIL INDICES OF AGRO-ECOSYSTEM AS AFFECTED BY LONG-TERM MONOCROPPING SYSTEM

Objectives: This study investigates nutrients stock and some soil indices of agro-ecosystem soil as affected by monoculture cropping system (cacao plantation). This was with a view to provide comprehensive understanding of soil nutrient dynamics in the ecosystems due to their different management practices. Methods: The study was carried out in 0.063 ha sample plots, three each in natural forests and cacao plantations adjacent to each other. In each plot, five core soil samples were randomly collected at two depths (0–15 and 15–30 cm), bulked according to depth, air-dried, sieved through 2 mm sieve, and analyzed for soil physicochemical properties using standard methods. One-way analysis of variance was used to test significant mean differences of the soil properties among cacao plantation and natural forest at probability level (p≤0.05) at different soil depth. Results: The results showed that soil physical properties such as particle size distribution, moisture contents, and bulk density; chemical properties such as pH, exchangeable cation, organic carbon, organic matter, phosphorus, and sulfur from natural forest were higher than the soil properties in cacao plantation for both top and subsoil. Soil indices such as soil structural stability index, base saturation percentage, and sodium adsorption ratio were higher in natural forest ecosystem than the soil indices of cacao plantation. Conclusion: From this study, it can be concluded that long-term monoculture cropping system had significant effect on nutrients stock and soil indices. This subsequently might result in permanent soil degradation and productivity.

Linking plant and soil indices for water stress management in black gram

Measurement of plant and soil indices as well as their combinations are generally used for irrigation scheduling and water stress management of crops and horticulture. Rapid and accurate determination of irrigation time is one of the most important issues of sustainable water management in order to prevent plant water stress. The objectives of this study are to develop baselines and provide irrigation scheduling relationships during different stages of black gram growth, determine the critical limits of plant and soil indices, and also determine the relationships between plant physiology and soil indices. This study was conducted in a randomized complete block design at the four irrigation levels 50 (I1), 75 (I2), 100 (I3 or non-stress treatment) and 125 (I4) percent of crop’s water requirement with three replications in Urmia region in Iran in order to irrigation scheduling of black gram using indices such as canopy temperature (Tc), crop water stress index (CWSI), relative water content (RWC), leaf water potential (LWP), soil water (SW) and penetration resistance (Q) of soil under one-row drip irrigation. The plant irrigation scheduling was performed by using the experimental crop water stress index (CWSI) method. The upper and lower baseline equations as well as CWSI were calculated for the three treatments of I1, I2 and I3 during the plant growth period. Using the extracted baselines, the mean CWSI values for the three treatments of I1, I2 and I3 were calculated to be 0.37, 0.23 and 0.15, respectively, during the growth season. Finally, using CWSI, the necessary equations were provided to determine the irrigation schedule for the four growing stages of black gram, i.e. floral induction-flowering, pod formation, seed and pod filling and physiological maturity, as (Tc − Ta)c = 1.9498 − 0.1579(AVPD), (Tc − Ta)c = 4.4395 − 0.1585(AVPD), (Tc − Ta)c = 2.4676 − 0.0578(AVPD) and (Tc − Ta)c = 5.7532 − 0.1462(AVPD), respectively. In this study, soil and crop indices, which were measured simultaneously at maximum stress time, were used as a complementary index to remove CWSI constraints. It should be noted that in Urmia, the critical difference between the canopy temperature and air temperature (Tc − Ta), soil penetration resistance (Q), soil water (SW) and relative water content (RWC) for the whole growth period of black gram were − 0.036 °C, 10.43 MPa and 0.14 cm3 cm−3 and 0.76, respectively. Ideal point error (IPE) was also used to estimate RWC, (Tc − Ta) and LWP as well as to select the best regression model. According to the results, black gram would reduce its RWC less through reducing its transpiration and water management. Therefore, it can be used as a low-water-consuming crop. Furthermore, in light of available facilities, the farmer can use the regression equations between the obtained soil and plant indices and the critical boundaries for the irrigation scheduling of the field.

METHOD OF FORECASTING THE YIELD OF APPLE TREES DEPENDING ON THE SOIL CONDITIONS OF THE NORTH OF THE CENTRAL CHERNOZEM REGION

The following soil indices that determine the level of apple tree yield have been determined: agrochemical indi-ces: pHKCl, hydrolytic acidity, total exchangeable bases, alkali-hydrolyzable nitrogen, easily-hydrolyzable nitrogen, mobile phosphorus, exchangeable potassium, humus con-tent, and ground water mineralization; morphological indi-ces: humus horizon thickness (A + B1), root layer thick-ness, carbonate depth, gleying depth, ground water depth, water-soluble salt depth; physical indices: soil density, mesoaggregate content (0.25-10 mm), physical clay con-tent (< 0.01 mm); water-physical indices: hydroscopic mois-ture, maximum hygroscopic content, capillary moisture capacity, minimum water capacity, available moisture, wa-ter stability coefficient; orographic indices: slope steepness and slope exposure. A method for predicting apple tree yield for soil types in the northern part of the Central Cher-nozem Region has been developed; the method is based on the agrochemical, morphological, water-physical, and orographic soil indices and takes into account the rootstock vigor. The method shows the range of the expected aver-age annual yield of apple trees during the period of full fruiting without fertilizer application. According to the devel-oped software, the highest yield of apple trees on semi-dwarf rootstock (using the example of 62-396) will be ex-pected on typical chernozems; on medium-sized rootstock (54-118) -on leached chernozems, podzolized and dark gray forestsoils; on strong-growing rootstock (pomaceous) -on podzolized chernozems and dark gray forest soils.