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Till-system management technology (TSMT) in soybean farming at Iran.

Introduction

Good root system development is essential for optimum wheat (Triticum aestivum L.) grain yield, especially under water-limiting conditions. Published information about the influence of tillage system on root dynamic and their effect on grain yield in Mediterranean rainfed Vertisols is scarce. A three-year field study was conducted on a typical Mediterranean rainfed Vertisol to determine, using a minirhizotron system, the effects of tillage system on root growth and grain yield in wheat. Tillage treatments were no-tillage (NT) and conventional tillage (CT). The parameters measured were root length (RL) and root diameter (RD) for 6 depths. Minirhizotron measurements were performed at 5 wheat growth stages. The RL was greater under NT than under CT for most growth stages and depths, this being the key to its greater grain yield (3.2 vs 3.0Mgha-1, respectively). The RD was not significantly affected by the tillage treatments, but was lower from stem elongation onward and during the dry years. The key to the development of a good wheat root system is the rainfall received during the tillering stage, regardless of soil water content at planting and rainfall before or after this growth stage. Under the rainfed Mediterranean Vertisol studied, wheat productivity is greater under NT due to better root system development. A mesorhizotron and scanning system was modified to study the development of Russian thistle root systems during the 1996 and 1997 growing seasons at Lind, WA. The imaging equipment combined the full profile images afforded by conventional rhizotrons with the portability of cylinder based minirhizotron systems at a fraction of the cost of either system. Root development of Russian thistle in early spring was rapid and extensive compared with shoot growth. In 1996, 30 d after planting (DAP) Russian thistle roots were at least five times as long as the corresponding plant's shoots. During the next 20 d, shoots grew a maximum of 20 cm, whereas roots grew a maximum of 120-cm deep. Maximum root elongation rate reached 2 to 3 mm/cm2/d at the 70- to 120-cm depths 30 to 50 DAP in 1996 and 55 to 70 DAP in 1997. More than one (multiaxial grouping) Russian thistle root was often observed growing through the same soil channels. After the rapid early season growth, roots began to shrink or die back until shoots were clipped to simulate wheat harvest. Within 7 d after harvest, roots regenerated in old root channels. The mesorhizotron system is a promising inexpensive tool for monitoring root morphological development of Russian thistle under field conditions [2]. Knowledge of soybean [Glycine max (L.) Merr.] primary, secondary, and tertiary root tip locations in the soil vs. seasonal time would enhance modeling of soybean development. The seasonal progression of root tip development and shoot phenology was evaluated in situ using an imaging device inserted into minirhizotron tubes installed in the soil at an in row 30[degrees]angle. Primary root tip extension was linear (i.e., 1.5 and 1.2 cm d-1 each year) until the full-seed stage. Emergent 5-mm secondary roots were routinely detected about 10-cm above the primary root tip, and thus present in a soil layer 11 d after the primary root tip had passed through that layer. Secondary roots followed a similar temporal pattern. Primary root tip location in the soil paralleled a 17[degrees]C soil temperature isoline. The 3.7-d phyllochron of main-stem node accrual between first node and seed fill may be a calibratable proxy for inferring correspondent root tip depths. Predicting the soybean rooting depth is necessary to project the maximum depths of water depletion in the soil profile. This information will allow a better estimation of irrigation requirement when using a soil balance approach. The objectives of this study were: 1) to monitor soybean rooting parameters and soil water depletion at 15-cm depth increments to 1.2 m and 2) to investigate whether there is a predictable relationship between the above-ground and belowground phenology. Soil matric potential sensors were installed at 15-cm increments up to 1.2 meters in non-irrigated field plots located on the University of Nebraska-East Campus during two seasonal rain fall differing years (2009-2010). Clear acrylic tubes were installed nearby at 30-degree angle in every 4th row. Root imaging and scoring of phenology were carried out bi-weekly from emergence to seed-fill. Taproot depth into the soil increased linearly with time. The depth at which 5-mm long secondary roots emerged from the taproot was also linear, and also the depth when 2-mm long tertiary roots appeared, was also linear with time. The successive appearance of main stem nodes (Vn) was linear from the V1 stage to reproductive development R5 stage. Rooting depth at R3-stage, a critical R-stage for irrigation scheduling exceeded 100-cm in each year. Therefore, the aim of this study was monitoring soybean root development under till-system management (TSM) at dry-farming conditions.

Materials and Methods

In order to tillage system management (TSM) for achieved to the optimum yield of soybean in dry-farming conditions, this experiment was carried out using by a factorial design with four replications. The factors were till-systems including no-tillage (NT), minimum tillage (MT), full tillage (FT) and conventional tillage (CT) and were studied the effects of tillage system on root growth and grain yield in soybean. The root development features were root length and root diameter at 5 soybean growth stages.

Results and Discussion

The root length was increased under no-tillage than under conventional tillage and the root diameter wasn't significantly affected by the tillage systems. The best of root system development in soybean was achieved during the stem elongation stage under no-tillage system. Therefore, monitoring soybean root development showed that tillage system management is very important in dry-farming, because in arid and semi arid weather the water resources are limited, so no-tillage system is a good system for farming in these conditions (Figures 1, 2, 3, 4 and 5).

References

[1.] Veronica Munoz-Romero, Jorge Benitez-Vega, Luis Lopez-Bellido, Rafael J. Lopez-Bellido, 2010. Monitoring wheat root development in a rainfed vertisol: Tillage effect. Europ. J. Agronomy, 33: 182-187.

[2.] William L. PAN, Frank L. Young and Ronald P. Bolton, 2001. Monitoring Russian Thistle (Salsola iberica) Root Growth Using a Scanner-Based, Portable Mesorhizotron. Weed Technology, 15: 762-766.

[3.] Jessica A. Torrion, Tri D. Setiyono, Kenneth G. Cassman, Richard B. Ferguson, Suat Irmak and James E. Specht, 2012. Soybean Root Development Relative to Vegetative and Reproductive Phenology. Agronomy Journal, 104(6): 1702-1709.

[4.] Jessica Torrion, Tri D. Setiyono, Kenneth Cassman, Suat Irmak, Daniel Walters, Richard Ferguson and James Specht, 2010. International Annual Meeting, Oct 31-04 Nov 2010, Long Beach, CA.

Behzad Sani

Behzad Sani, Department of Agriculture, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran

Corresponding Author

Behzad Sani, Department of Agriculture, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
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Title Annotation:Original Article
Author:Sani, Behzad
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:7IRAN
Date:Mar 1, 2013
Words:1123
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