JOURNAL OF AGROECOLOGY (کشاورزی بوم شناختی)
Year:2012 | Volume:2 | Issue:1|Papers Count:10

Crop simulation models have been widely used to simulate growth and development of crops under various production situations. Sugar beet is one of the most important field crops in Iran particularly in Khorasan province. This study aimed to modify SUCROS model (that only simulates potential and water-limited crop growth) for using under nitrogen-limited conditions. Accordingly, a simple subroutine for nitrogen balance was added to the previous version. So, the new model dubbed as SUCROSBEET, is an adapted version of the old one, including nitrogen limitation. Nitrogen stress in the new model was defined through the nitrogen nutrition index (NNI): the ratio of actual nitrogen concentration and critical nitrogen concentration in the plant. This paper describes the model and details of model calibration and testing using independent data sets of nitrogen treatments (with fertilizer rates of 0-270 kgN ha-1) under varying environmental conditions. In general, the model responded well to nitrogen stress in all the treatments. However, the model underestimated the growth at lower level of nitrogen application and overestimated at higher levels. The simulated average yield was somehow similar to its observed value with root mean square error of 9 Mg ha-1. It is concluded that the modified model could be reasonably used to simulate sugar beet yield under both potential and N-limited situations. Also, the enhancement of its capability is enabled the model to estimate yield gap and agro-zonning at a national scale.

This study was done to evaluate different nonlinear regression models to describe response of germination rate to temperature in Brassica napus L. (canola), Sinapis arvensis L. (wild mustard), Raphanus raphanistrum L. (wild radish), Descurania sophia L., Phalaris minor L. (phalaris). This experiment based on completely block randomized design with 3 replications at Plant Research Institute (Dep. of Weed Research) laboratory in 2011. The seeds treated with different temperatures (0, 5, 10, 15, 20, 25, 30, 35, 40 and 45oC) and the germination rate were calculated. The result showed that temperature had significant effect on germination rate of all plants. Tree regression models (Dent-like, Segmented and Beta) used to predict germination rate and cardinal temperature. Root mean square of error (RMSE), coefficient of determination and corrected AKAIKE index (AICc) were used to find the appropriate model (s). Therefore segmented model were superior compared to other models in canola and all weeds. It was concluded that this model can be used to quantify response of common weeds of canola field germination to temperature and to obtain cardinal temperature of germination. Base (Tb), optimum (To) and ceiling (Tc) temperature were predicted with appropriate models. Tb, To, Tc were for canola 1.8, 25, 40.9; wild mustard 2.01, 15, 30.6, wild radish 1.9, 15, 30.1, D. sophia 1.2, 26.9, 35 and phalaris 1.9, 15.5, 30.3 respectively. These parameters are required to predict common weeds of canola field germination and emergence.

Nitrogen (N) fertilizer that used to raise seed yield can affect weed competition. In order to study the effect of N arte and growth habits on dry bean competitiveness, a two-year field experiment as complete block design were conducted with factorial arrangement and three replications at a field experiment of Tarbiat Modares University in 2009 and 2010. First factor included determinate erect (cv. D81083) and indeterminate semi-erect (cv. Gholi) dry bean growth habits. Second factor was N application rates at 0, 25, 50 and 100% of recommended N rate on the basis of the grain yield goal for each genotype. Third factor was redroot pigweed densities of 0, 2 and 14 plants m-1. N application increased leaf chlorophyll and leaf area index for both bean genotypes when they grown under no and low weed density. Under high weed density, the maximum N application compared with no N application increased leaf chlorophyll for Gholi cultivar; however leaf chlorophyll for D81083 line increased at 50 and 100 % of maximum N requirement. Under high weed pressure, N application had no significant effect on leaf area index for D81083 line and decreased the leaf area index for the Gholi cultivar. The increase of weed density decreased leaf area index in both bean genotypes. An increase in N fertilizer increased seed number and see yield for both bean genotypes when they grown under no and low weed density. The maximum seed yield loss associate with redroot competition obtained at high N rate and high weed pressure.

In this research, in order to evaluate morphological diversity of wild oat populations, Principal component and cluster analyses were used in 59 populations of Avena fatua and Avena sterilis ssp. ludoviciana which were sensitive or resistant to ACCase inhibitor herbicides and belonged to different parts of Iran, using 20 quantitative and 12 qualitative characters. With the principal component analyses, the first 7 principal component contributed 72.97% of the variability amongst populations, which justified following characters, respectively: the first principal component (with 21.97% of the total variation) rachis length, panicle length, ligule length and leaf width characters, the second principal component (with 16.26% of the total variation) length of spikelet without awn, upper and lower glume length characters, the third principal component (with 10.27% of the total variation) upper and lower glume width, teeth of lemma ending length of first floret and callus length characters, the fourth principal component (with 7.28% of the total variation) number of nerves in the upper glume, awn length in the first floret and number of nerves in first floret lemma characters, the fifth principal component (with 6.27% of the total variation) number of nerves in the lower glume, lemma length in the first floret and palea length in the first floret characters, the sixth principal component (with 5.62% of the total variation) rachila length character and seventh principal component (with 5.28% of the total variation) number of florets. Cluster analyses showed high morphological variation while no relationship between genetic divergence and geographical origins in populations was observed. Moreover, it was shown that dendrogram of cluster analyses based on qualitative traits, can differentiate two studied taxons and neither qualitative nor quantitative characteristics could separate populations based on their resistance to ACCase inhibitor herbicides. Results of this research can be useful in the genus Avena and it’s species germplasm management in Iran.

In order to evaluate response of Pishgam wheat cultivar to manure and biological substrate, a factorial experiment based on RBCD (randomized complot block design with 3 replications was done. The first factor was manure with three levels including 0, 7.5 and 15 ton per hectare, and second factor was biological substrata consumption including 0, 3 and 5 times. Traits under study were plant height, ear length, number of ear per square meter, number and weight of kernel in ear, 1000 kernel weight, biological and economical yield and also harvest index. Analysis of variance showed that manure had significant effect on all traits except plant height and ear length. By increasing of manure consumption from 7.5 to 15, yield component were increased. Effect of biological substrate on plant height, kernel weight in ear and 1000-kernel weight, was significant (P≤0.01). Maximum economical yield was obtained from 3 times biological substrate consumption and 15 tons manure with 26.6% increase compare to check treat. Highest biological yield was gained from 7.5 tons manure and 3 times biological substrate treatment and also the highest harvest index was earn from 7.5 tons manure and 5 times biological substrate treatment with 24.6% and 5% increasing respectively compare to check. It seems biological substrate effects in fertile soils is lower than non-fertile soils.

In order to evaluate the effect of biological fertilizers on the yield and yield components of three sesame cultivars (Sesamum indicum L.) an experiment conducted in the 2010-2011 in the form of split plots with randomized complete block design with three replications. Three cultivars of Sesam (Kalat, Esfarayen and oltan) allocated to the main plot and three biological fertilizers (nitroxin (A), phosphate solubizing bacteria (B), A+B and control) allocated to sub plot. Parameters such as SPAD readings, Leaf Area Index (LAI), Crop Growth Rate (CGR), Net Assimilate Rate (NAR), biological and economic yield, Oil content and yield, plant high, number of auxiliary branches, number of pods per plant, number of seeds per pod and 1000 seed weight were measured. Most of these parameters were not affected by the fertilizer treatments. However, there were significant differences between varieties. nitroxin+biophosphor measured plant height observed with nitroxin application. In this experiment, sesame did not respond to biological fertilizers properly and this seems to be associated with the nature of this plant and the fertilizer soil conditions and the status of biological.

In order to identify the population index and weed mapping in Ardekan and Meybod pomegranate and pistachio gardens in Yazd province, by using of Geographic information system (GIS), 120 gardens were sampled. (30 pistachio garden and 30 pomegranate in Meybod and 30 pistachio and 30 pomegranate garden in Ardekan) in 2011. In each garden longitude, latitude and altitude were recorded by means of GPS. Recorded data made weed maps in the GIS. Weed flour contains 55 species from 22 families that 29 and 40 species were in pomegranate gardens of Ardekan and Meybod respectively, and 36 and 39 species were in pistachio gardens of Meybod and Ardekan respectively. The most important families of weed in pistachio and pomegranate gardens were Poacea, Asteraceae and Fabaceae. Shannon-Viener Index was used In order to comparison of gardens species diversity and uniformity. Results showed high weeds uniformity in two counties because of same weather, climate and gardeners management methods. From Abundance Index (AI) point of view, Broadleaf weeds includes, field bindweed (Convolvulus arvensis L.), common lambsquarters (Chenopodium album L.), Russian knapweed (Acroptilon repens (L.) DC.), camelthorn (Alhagi persarum Bioss. & Buhse.), and grass weeds include, giant green foxtail (Setaria viridis (L.) P.Beauv.), rigid rye grass (Lolium rigidum Gaud.), little seed canary grass (Phalaris minor Retz.), Bermuda grass (Cynodon dactylon (L.) pers.) were the most important and dominant species.

The aim of present study was to assess sustainability and to understand factors that may influence this characteristic by using framework for evaluation sustainable land management (FESLM) in vineyards of Qazvin Province, Iran. Data required to the research were collected by questionnaire and face to face interview with grape orchardists. The statistical population of the research was grape orchardists in Takestan county of Qazvin province from whom 220 orchardist were chosen by stratified random sampling with proportional allocation method. Results showed that for the productivity aspect low performance of irrigation, inappropriate congestion of grape bushes and excessive use of external inputs have led to a unsustainable situation. For the security scale, the high insurance coverage of farmers has provided a relatively sustainable situation. For the viability, due to variation in product sales, market demand existence, diversification of income sources and increasing trend in price of grape and its byproducts, the situation is relatively sustainable. For the protection scale, due to low technical knowledge of the grape orchardists, excessive use of fertilizers and chemical pesticides and increased water loss, there is an unsustainable situation. For the acceptability aspect, access to appropriate facilities and services and interest to gardening activity in grape orchardists has led to a relatively sustainable situation. In general, to improve productivity and to protect the grape production ecosystems, use of drip irrigation systems, trelliswork of orchards and training farmers with integrated management techniques for controlling pests, diseases and weeds in the farmer field school, was proposed.

In order to study the possibility of broomrape (Orobanche aegyptiaca L.) control in tomato fields, with using herbicides and nitrogen fertilizers, a field experiment counducted at Savojbolagh in 2008. A randomized complete block design with a split plot layout was used, with 4 replications. Using the nitrogen fertilizers (Ammonium sulphate equal 500 kg ha-1, urea equal 200 kg ha-1 and no fertilizer) were the main plots and application of postemergence herbicides (methsulfuron methyl + sulfosulfuron at 32 g a.i ha-1, sulfosulfuron at 18.7, 37.5 g a.i ha-1, rimsulfuron at 7.5, 15 g a.i ha-1 and not herbicide using) were the sub plots. All herbicides were used 30, 40, 50 days after tomato transplanting in fields. The results showed glyphosate caused no damages on tomato plants and provided best control of broomrape. Sulfosulfuron 18.7 and 37.5 g a.i ha-1, rimsulfuron 7.5 and 15 g a.i ha-1 and methsulfuron methyl + sulfosulfuron 32 g a.i ha-1 had no effect on broomrape control. Using ammonium sulphat and urea with and without combination herbicides had no effect on broomrape control.

Prediction of the leaf area is essential in crop simulation models. The objective of this study was to find relationships between leaf area index (LAI) and numbers of leaves (NL), leaf dry weight (LDW), leaf fresh weight (LFW), number of nodes (NN) and plant height (PH), in Pumpkin (Cucurbita pepo L.). For this purpose, an experiment was conducted using three planting dates (20 April, 21 May, 21 June) at the research field of Aburaihan Campus, the University of Tehran, Pakdasht, Tehran, Iran, in 2009-2010 cropping season. The experimental design was randomized complete block with four replications. Sampling was performed during the whole growing season. In each sampling LA, NL, LDW, LFW, NN and PH, were measured. Various equations were used to describe relationships between LAI and aforementioned characteristics. The best result was obtained a simple ln-transformed linear equation {ln(y)=a+b×ln(x)}. Results showed that significant relationships were found between LAI and LA (R2=90), LAI and NL (R2=90), LAI and NN (R2=90), LAI and LDW (R2=98) and LAI and LFW (R2=98). These equations LAI can be used for estimation in simulation models of Pumpkin as well as for the fast and easy estimation of LAI, especially where there is no LAI-meter available.