کربن آلی

Nowadays, agricultural products are moving towards organic farming in response to consumers' desire for healthier products. One of the ways to produce and increase yield in these conditions is using biological and organic inputs such as biochar and mycorrhiza. Therefore, this experiment was conducted at Safadasht Golazin Agro-industrial in Safadasht, Tehran, in order to investigate spinach yield. The experiment was carried out as split plots in the form of a randomized complete block design in 3 replications. The experimental treatments included four levels of control, two, four, and six tons per hectare of biochar as the main factor and two inoculation levels with mycorrhiza and control as secondary factors. The results showed that the effect of the investigated treatments on the measured traits was significant. The highest plant height (15.24 cm), total chlorophyll (2.44 mg/g fresh weight), root fresh weight (19.56 g), and shoot (30.95 g) at the application level of mycorrhiza and six tons of biochar per hectare was observed. The effectiveness of mycorrhiza increased with the increase of biochar level. In general, the results showed that the synergism effect of biochar and mycorrhiza increased the yield of spinach traits; this synergy can be one of the strategies to reduce the consumption of chemical fertilizers.

There is an urgent need to increase per capita food production to compete with high population growth while maintaining environmental sustainability. Because nitrogen plays a vital role in food production for humans and livestock, nitrogen management is essential in food production. In most cropping systems, nitrogen management seems to be a major challenge due to its high mobility and natural tendency for losses from the soil-plant system to the environment. Soil organic carbon plays a key role in improving soil ecological conditions. Adding organic matter to the soil is an excellent tool for improving physical, chemical and biological conditions and is almost always desirable. Soil organic carbon stock of crop ecosystems may be increased by improving farming practices. The application of green manure, fertilizer and the return of crop straw into the soil are known as management operations to increase soil organic carbon. Fertilizers, especially nitrogen, increase crop yield, and organic carbon is returned to the soil through roots and debris, which in most cases leads to increased soil organic carbon.

This study was conducted with the aim of utilizing a set of improving farming practices in diverse cropping systems to improve nitrogen efficiency during two crop years. Farming practices including removal of summer fallow were used by importing three crops of mung bean, corn and wild rocket in rotation plus nitrogen supply levels factor. The crop rotation factor was applied in four levels of Fallow-wheat, mung bean-wheat, corn-wheat and wild rocket-wheat and the factor of nitrogen fertilizer (0, 180 and 360 kg.ha-1) in a randomized complete block design as factorial. Soil mineral nitrogen (nitrate and ammonium) were measured before sowing wheat and grain, straw and total plant nitrogen after harvest. Uptake efficiency, utilization efficiency, agronomic efficiency and nitrogen harvest index were calculated.

The results of combined analysis of variance showed that the crop rotation and nitrogen were significantly effective (ρ ≤ 0.01) on plant nitrogen, harvest index and nitrogen efficiency. Increasing nitrogen fertilizer up to 360 kg.ha-1 increased grain nitrogen, straw nitrogen, total plant nitrogen and also nitrogen harvest index. While the best uptake, utilization and agronomic efficiency of nitrogen was observed on the treatment without nitrogen fertilizer. Comparison of the means showed that the wild rocket-wheat crop rotation had the best result among all measured traits except utilization efficiency, while the utilization efficiency in the corn-wheat crop rotation showed the best performance. The results clearly show the effect of increasing organic carbon on nitrogen availability and grain nitrogen concentration as well as the role of cover crops and legume, in increasing access to nitrogen. The amount of grain nitrogen was directly affected by the amount of nitrogen fertilizer. The highest correlation coefficient was seen between agronomic and uptake efficiency (r = 0.96**). There was also a significant inverse relationship between nitrogen harvest index and the types of calculated efficiencies. The amount of uptake efficiency and agronomic efficiency in all crop rotations except corn-wheat in the second year improved compared to the first year. The highest increase in efficiency in the second year was related to the wild rocket-wheat crop rotation. In the conditions of 360 and 180 kg.ha-1 nitrogen fertilizer, the nitrogen harvest index increased in the second year compared to the first year. While in conditions without nitrogen fertilizer, nitrogen harvest index has a significant decrease. Therefore, at least in the short term, to increase the nitrogen harvest index, the minimum supply of nitrogen fertilizer should be used, even under improving crop management conditions such as green manure, removal of fallow and introduction of legumes in rotation and return of crop residues.

Continuous cropping, removal of fallow, use of cover crops and legume and preservation of residues led to increased carbon and nitrogen sequestration in soil and consequently increase biomass and nitrogen concentration in plant tissue. On the other hand, crop rotations that increased soil organic carbon and improved soil fertility quickly improved nitrogen efficiency and nitrogen harvest index.

In order to investigate the effects of compost and nitrogen on quantitative and protein content of forage corn and some physical and chemical properties of soil, a factorial experiment with 9 treatments in a factorial randomized complete block design has been conducted in the farm of Tehran Agricultural and Natural Resources Research and Education Center during 2014. The treatments include three levels of residual compost (0, 10, and 20 Ton.ha-1) and three levels of nitrogen (0, 100, and 200 kg.ha-1) as urea. The effect of municipal waste and nitrogen compost on yield and yield components has been significant. The use of municipal solid waste compost has significantly increased the electrical conductivity of soil, nitrate, iron, and zinc uptake, while significantly decreasing soil reaction. Waste compost application has also improved some soil physical properties. Bulk density is significantly reduced and field capacity and soil available water are increased. Therefore, in the similar soil conditions of this ersearch, the use of 200 kg.ha-1 of pure nitrogen from the urea source with 20 Ton.ha-1 of municipal solid waste compost is recommended to achieve the maximum dry forage yield of 21.44 tons per hectare.

Crops cannot be sustainably produced by the exclusive use of chemical fertilizers nor can higher crop yield be obtained by using organic manure alone. Sustainable crop production is possible through some approaches such as suitable crop sequence and also the integrated use of organic manure and chemical fertilizers. Therefore, the mail goal of this study is evaluation the effect of crop sequence as double cropping system and integrated chemical and biological fertilizer on quantity and quality yield of wheat and also its soil chemical nutrients. This experiment was conducted at 2015 – 2016 in research field of Shahid Chamran University of Ahvaz. Experimental design was split plot based on RCB with three replications. Main plot was 5 double cropping systems including 1: sunflower- wheat, 2: millet – wheat, 3: maize – wheat, 4: sesame – wheat, 5: mung bean – wheat. Also, sub-plot was 3 fertilizer managements including 1: full chemical fertilizer, 2: full biological fertilizer, 3: integrated biological and chemical fertilizer. Grain yield and yield components of wheat was measured. The SAS software was used to analyses the results and Duncan methods for comparison of means. Both parameters of main ear weight (1/96 gr) and number of grain in ear (31/7) were obtained in planting mung bean before wheat. But, planting of sesame before wheat had lowest main ear weight (1/63 gr). Also, planting millet before wheat had lowest number of ear /m2 (443/6 ear/m2). In addition, characters that basically formed at early growth stage of wheat (e.g. number of ear per m2) had mostly affected by type of crop in rotation in compared than characters which formed at middle of growth stage (e.g. number of grain in ear). Present of mung bean as a legume crop caused a highest main ear weight due to highest grain per ear (31/7 grain/ear). Highest and lowest of all yield components (exception for number of ear per m2) were obtained in full chemical and full biological fertilizer management, respectively, which showed that relaying on full biological fertilizer management will not enough for obtaining the maximum crop yield. In most cases, straw yield had not affected by type of crop which planted before wheat. However, millet – wheat double cropping system had a lowest straw yield (6/22 t/ha). Also, the highest (7/57 t/ha) and lowest (6/61 t/ha) straw yield was belonged to full chemical and biological fertilizer management, respectively. In addition, the highest (0/1 %) and lowest (0/073 %) soil nitrogen was belonged to sequence of sunflower – wheat and sesame – wheat which treated by integrated fertilizer management. Also, present of sunflower, millet, maize and mung bean crops before wheat, caused by higher soil phosphorus in full biological fertilizer management than other fertilizer systems. Both treatments including type of crops before wheat and Fertilizer management had significant effect on wheat grain yield and yield components. Effect of previous crop in double cropping system had changed with change in fertilizer management from chemical to biological form. But, in short period, effect of fertilizer management was more effective than crop rotation. Highest wheat grain yield was obtained in mung bean – wheat double cropping system with and without integrated fertilizer management (i.e. 7/1 and 5/9 t/ha). Also, millet – wheat double cropping system had a lowest (0/051 %) soil nitrogen. Therefore, we concluded that in rotation with legume crops, integrated fertilizer management will better than both full chemical and full biological fertilizer managements.

IntroductionThe impact of agronomy on the subsequent product in rotational cropping systems depends on factors such as plant type, duration of crop growth, soil moisture content, tillage type, irrigation method, the amount of nitrogen fertilizer, quantity and quality of returned crop residues to the soil. Prior cultivated crops improve the next crop yield by causing different conditions (nitrogen availability, organic matter and volume of available water) in soil. This study was conducted due to importance of corn cultivation in Khuzestan and necessity of increasing the soil organic matter, moisture conservation and in the other hand the lack of sufficient information about the relationship between soil texture, type of preparatory crop in low-tillage condition and some soil characteristics and corn growth habits. The purpose of this experiment was to evaluate the effect of residue of preparatory crops in low plowing condition in two soil types on corn yield and some soil characteristics.
Materials and MethodsThis experiment was carried out at Shooshtar city located in Khuzestan province. An experiment was performed by combined analysis in randomized complete block design in two fields and in two consecutive years with four replications. Two kinds of soil texture including: clay loam and clay sand. Five preparatory crops including: broad bean, wheat, canola, cabbage and fallow as control assigned as sub plots. SAS Ver. 9.1 statistical software was used for analysis of variance and comparison of means. Graphs were drawn using MS Excel software. All means were compared by Duncan test at 5% probability level.
Results and DiscussionThe soil texture and the type of preparatory crop influenced the characteristics of the soil and corn grain yield. Returning the broad bean residue into two types of soil caused the highest grain yield of corn 10128.6 and 9547.9 kgha-1, respectively. The control treatment in sandy loam texture had the lowest corn seed yield (6111 kg.ha-1). Therefore, in these conditions, amount of plant residues and soil texture have played an important role in improving the soil quality and corn yield, which would be lead to economic objectives of sustainable and low input and cost production. Treatment of broad bean residues in depth of 0-15 cm resulted to the highest total nitrogen of 0.121% in clay loam soil and 0.122% in loam sand soil. The return of broad bean plant residues in both soil types improved corn grain yield which can be attributed for fixing and increasing the soil nitrogen by broad bean and decrease the ratio of carbon to nitrogen in soil. It seems that the contribution of broad bean residues released nitrogen gradually, particularly at the end of corn growing season.
The results showed that treatment of wheat residues in clay loam soil had the highest carbon to nitrogen ratio (8.10%), and in sandy loam soil, treatment without plant residues had the lowest ratio of carbon to nitrogen (1.4%). Increased carbon/nitrogen ratio was the result of high ratio of carbon content to nitrogen in wheat. Burying the remains of wheat and canola led to significant decrease in soil nitrogen during growing season and a sudden increase in soil organic carbon.
Mean comparisons showed that adding wheat residues to clay loam soil had the lowest soil bulk density in depth of 0-15 cm (1.19 gcm-3) and treatment of control (no adding plant residues) to sandy loam soil had the highest soil bulk density (1.54 gcm-3). The lowest soil bulk density was observed in depth of 0-15 cm and with increase in depth, soil bulk density increased, too. It seems that high percentage of the soil moisture can lead to low soil bulk density. Combination of clay loam soil with wheat, canola and broad bean residues caused soil moisture content of 21.3%, 20.4% and 20.5%, respectively, while returning the residue of cabbage did not have a significant influence on soil moisture in comparison with control (12.9%).
ConclusionsIn general, mixture of broad bean residues with both soil types had the positive effects on corn yield and soil characteristics compared to other crop residue.

This experiment was done to evaluate the effects of soil tillage methods on chemical and biological properties of the soil along with quantitative traits of silage corn after chickpea as a preceding or companion crop. The experiment was conducted for two cropping years of 2013-15 at farm of Tehran University. The experiment was set up as a split plot in RCBD in four replications. The main factor considered three soil tillage methods (conventional, minimum and no-tillage) and the sub-factor included three varieties of maize (SC704, Zp677, Maxima). The experimental units covered by chickpea residue by at least 30 percent of the surface area. Results showed that the no-tillage and minimum tillage treatments had higher amount of soil organic carbon, pH and number and body mass of earthworm than the conventional tillage treatment. Tillage treatments had no significant effect on measured soil total nitrogen, electrical conductivity and sodium. Also, the highest maize wet and dry stem weight (691.5 and 1866.5 gm-2), Ear dry weight (664.4 gm-2) and total plants wet weight (4896.9 gm-2) observed in Zp677 maize cultivar. Conventional and minimum tillage methods had significant effects on leaf and ear wet and dry weights and total plant dry weight traits. Thus, in the 2nd year of this experiment, no-tillage was more effective than other tillage methods. But, there was no significant effect between no-tillage and conventional tillage treatments in the second year. According to the results, both conservation tillage methods is recommended as replacement methods for conventional tillage in maize/chickpea rotation.

In order to study the effects of tillage systems and wheat residue levels on soil physical, chemical and biological characteristics a randomized complete block design arranged in split block with three replications was set in research farm of Ferdowsi University of Mashhad in 2013-2014 growing season. Four different tillage systems (disk, mouldboard plough disk, sweep plough disk and chisel plough disk) as vertical factor were employed in combination with five different crop residue applications (0, 25, 50, 75 and 100 percent wheat residue) as horizontal factor. Due to soil sampling in April (2013), November (2013) and June (2014), data were analysed as split block in time. According to the results, the lowest total nitrogen (0.094%), available phosphorus (12.50 mg/kg) and organic carbon (0.52%) were observed when mouldboard plough was applied, while the highest values were obtained using chisel plough followed by disk. Irrespective of sampling time, total nitrogen, available phosphorus and potassium as well as organic carbon significantly increased with increasing wheat residue application. Furthermore, crop residue application caused significant reduction in soil pH (up to 0.45 unit) and improved microbial biomass and activity (by 20.6%).

In order to study the effect of different green manure plants on soil organic carbon, phosphor, total and mineral nitrogen, an experiment was conducted over two years (2009 and 2010) based on randomized complete blocks design with four replications. The green manure treatments included sorghum (Sorghum bicolor), pearl millet (Panicum miliaceum), turnip (Eruca sativa), white clover (Trifollium repens), sainfoin (Onobrychis viciaefolia), red clover (T. pratense), berseem clover (T. alexandrinum), vetch (Vicia sativa), bitter vetch (Vicia peregrine) and oat (Avena sativa) plants. Changes in soil nutrient elements and nitrogen mineralization were measured during different time periods after plant residues incorporation to soil. At the first and second year the results indicated that sorghum and pearl millet green residues resulted in the highest amount of soil organic carbon after five months incorporation. At first year, the highest soil nitrogen content (0.23 %) was observed in white clover plant after five months incorporation and at second year has been derived by applying vetch green residues (0.34 %). At first year the C:N ratio significantly decreased after 3 months soil incorporation of white clover. At first year, the highest soil phosphor content (34.00 mg/kg) was obtained after five months incorporation of white clover plant while in second year the highest phosphorus content of soil obtained by applying vetch green residues. In conclusion white clover and vetch due to lower C:N ratio, higher total and mineral nitrogen and phosphor for subsequent plant, is introduced as proper green manure among studied plants.

This study was carried out at the research farm of Agriculture Faculty, Bu- Ali Sina university, in 2009, to evaluate the effect of winter cereals as cover crops on weed control, improving soil fertility, yield and yield components of potato. The experiment was a randomized complete block design with three replications. The trial including seven treatments consisted of no cover crop, rye, barley and triticale, each with common and triple plant density. The results showed that rye and barley with triple plant density produced 1503.5 and 1392.2 g/m2, respectively. Rye, barley, triticale with triple and rye with common plant density reduced winter weeds biomass 97, 96, 93 and 89 percent respectively, compared to control. Cover crop treatments showed different abilities to weed control in potato growth period (15, 45 and 75 Day After Germination) compared to the control treatment. The treatments, of rye and barley with triple and rye with common plant density had the most inhibition effects on summer weeds. Soil physical properties were affected significantly by cover crops, so rye, barley and triticale with triple and rye with common plant density, increased organic carbon 26, 25, 21 and 25 percent, respectively compared with the control treatment. Rye and barley with triple and rye with common plant density, decreased soil specific weight 6.6, 7.5 and 7.4 percent, respectively compared with the control treatment. There was a significant correlation between weeds plant population and the dry matter of potato, organic carbon percentage, soil specific weight and number of large potato tubers with potato tuber yield. Rye with common and triple plant density and barley with triple plant density compared to control increased tuber yield of potato 50, 33 and 35 percent, respectively. These treatments increased the number of large potato tuber 42, 33 and 27 percent, respectively compared with control.

To determine the effect of organic fertilizers together with chemical fertilizers as basic on crops yield and soil organic carbon، an experiment was carried out from 1997 to 2002 at Safi-Abad Agricultural Research Center of Dezful،Iran، in a wheat- potato - wheat - canola - corn rotation. The experimental design was a randomized complete block with a split - plot arrangement of treatments with nine treatments and in three replications. Also، in each replication an additional treatment as control plot (no application of organic fertilizer and only use of chemical fertilizers) was included. Organic fertilizer sources were as main plots consisting (farm yard manure، sugar cane bagas compost and wheat straw)، and organic fertilizer rates were as sub plots at 5، 10 and 15 t / ha. The results showed that effect of organic fertilizer amounts on canola grain yield and effect of organic fertilizer sources on potato yield were significant. As compared with control plot yield increases due to application of organic fertilizer in potato، corn، wheat and canola were about 1600، 1400، 750 and 500 kg/ha،respectively. Also، soil organic carbon increased significantly with organic fertilizer application. Therefore، application of FYM or sugar cane bagas compost at 5 t/ha in combination with optimum use of chemical fertilizers are recommended especially for potato and canola.

In order to study the effect of farming systems on three Iranian garlic clones (Allium sativum L.), an experiment was conducted with split plot arrangements in 3 complete blockes in the growing seasons of the year of two successive years of 2004- 2005 at the experimental farm of the Environmental Science Research Institute of Shahid Beheshti University. Two factors were evaluated in the experiment: (a) farming systems in three levels (intensive, traditional and organic farming), as the main plots and, (b) garlic clones in three levels (Atoo, Hamedan and Virani clones), as the sub-plots.Results showed that the farming systems had significant effect (p≤ 0.01) on percentage of organic carbon, organic matter, total nitrogen, the availability of phusforus, potassium, EC and pH of soil. Amount of these parameters were increased in transition from intensive to organic system with the exception of pH. The highest value of this parameters were obtained in organic systems. Farming systems had significant effect (p≤ 0.05), on number of plant and bulb yields, too. The highest and the lowest bulb yields were obtained in intensive (9.5 ton/ha) and organic(7.4 ton/ha) systems, respectively. Though the yield was reduced as a result of organic farming, however, positive effect on soil structure, which consequents increase yield in long term can be expected.