Nitrogen remobilization in wheat as influenced by nitrogen application and post-anthesis water deficit during grain filling

Pre-anthesis stored nitrogen in wheat (Triticum aestivum L.) is important because grain filling greatly depends on the remobilization of pre-anthesis nitrogen under Mediterranean growth conditions. This field study was conducted to assess the effect of post-anthesis water deficit and three N fertilizer levels on N remobilization and N losses in three wheat cultivars (‘Shiraz’, ‘Marvdasht’ and ‘Chamran’). Nitrogen remobilization in plant parts decreased to 29 to 58% under water deficit compared with the well watered (WW) treatment. Grain N was 40% higher under post-anthesis water deficit than the WW treatment and with the addition of 160 kg N ha-1. The application of nitrogen fertilizer increased N remobilization to 78%. ‘Shiraz’ remobilized 13 and 25% more nitrogen than ‘Marvdasht’ and ‘Chamran’, respectively. Under water deficit, N remobilization efficiency increased by 13%. Leaves were more efficient than stem and spike in N remobilization efficiency either in the WW or the WD treatment. The application of fertilizer N generally lowered whole plant remobilization efficiency. The N remobilization efficiency of ‘Chamran’ increased when the soil moisture and/or N were limited during the grain filling period. Grain N concentration was correlated positively with N concentration or N content of vegetative parts at anthesis. In addition to nitrogen fertilizer, WD during grain filling reduced nitrogen use efficiency by 30 and 25%, respectively. In the WW treatment, 25% of the N at anthesis was lost at maturity. In contrast, under WD only 6% of the N was lost. High amount of N led to N losses at maturity. Significant negative correlations were found between grain yield and grain protein concentration in the three wheat cultivars. Results indicate that the greater the amount of N accumulated before anthesis, the higher the translocation rates of nitrogen to grain and the greater the risk of net N losses at maturity.Key words: Nitrogen harvest index, nitrogen loss, grain protein, nitrogen use efficiency

Using boundary line analysis to assess the on-farm crop yield gap of wheat

Food security is one of the most important challenges facing human kind. A very promising approach to solve the problem is closing the yield gap, i.e. the difference between farmer’s and potential yield. A ‘complete yield gap assessment method’ must provide information regarding potential yield, actual yield and yield gap, the causes of the gap and their importance. The objective of this study was to indicate how boundary line analysis (BLA) could be applied to such an assessment. BLA was only applied to crop management practices/inputs, e.g. sowing date and rate and fertilizer applications. The data were gathered from about 700 wheat farms in Golestan province, one of the major wheat producing regions in Iran, during two growing seasons of 2013–2014 and 2014–2015. Wheat production in Golestan province can be divided into three production situations according to agro- and geo-climatology criteria: these are ‘irrigated or high-rainfall’, ‘high-yield rainfed’, and ‘low-yield rainfed’. Boundary lines were fitted to the edge of the data cloud of crop yield versus management variables using data from each of the three wheat production situations in the province. Actual farmers’ yields were 3900 kg ha–1 for irrigated, 4000 kg ha–1 for high-yield rainfed and 2000 kg ha–1 for low-yield-rainfed situations; BLA indicated that potential yields (the highest yields obtained by farmers in the sample) were 6900, 5800 and 3900 kg ha−1 for each situation, respectively. The corresponding yield gaps were high at 42%, 31% and 50%. Using BLA it was possible to determine the optimal sowing date, seeding rate, frequency and amount of nitrogen fertilizer applied, amount of nitrogen top-dressing, amount of phosphorus and potassium fertilizers and irrigation frequency. The percentage of farmers who cultivated outside of the optimal levels was also identified and was used to determine the importance of each management factor in yield gap. It was concluded that BLA as applied in the study, was a cheap and simple method which, without the need for expensive experimentation, was able to detect yield gaps and their causes in a region. The method can be used effectively in countries/regions where important yield gaps exist

Agricultural Academy

Abstract SABET, M., A. AYNEHBAND and A. MOEZZI, 2009. Genotype and N rates effect on dry matter accumulation and mobilization in wheat (Triticum aestivum L.) in sub tropical conditions. Bulg. J. Agric. Sci., In wheat, the supply of assimilate to grain originates from current assimilation transferred directly to kernels and from the remobilization of assimilates stored temporarily in vegetative plant parts. The field experiments were conducted at the experimental farm of Faculty of Shahid Chamran University of Ahvaz, Iran, during 2008-2009 growing seasons. Experimental design was split-plot, N rates as main plots and wheat cultivars as sub-plots. Different stem and internode weight and length, their effects and relationships among stem segments and dry matter accumulation and mobilization were measured at 10-d intervals in 4 old and modern wheat cultivars grown under different N rates. Our results showed that, the main effect of genotype, nitrogen rate and interaction of G×N were significant. Internode length, weight, and specific weight were increased with N application. Mobilized dry matter was more in no N application than in high N application for peduncle (157 vs. 113 mg), penultimate (200 vs. 140 mg) and the lower internodes (329 vs. 190 mg). High N application decreased mobilization efficiency, expressed as percentage of maximum dry mater mobilized, in the peduncle, penultimate, and the lower internodes by 28, 19, and 35%, respectively. Therefore, partitioning of stem reserves into different internodes and their specific weights, play a key role in differences between old and modern wheat cultivars for accumulation and mobilization of dry matters. In general, the old cultivar Chenab and modern cultivar Dena showed relatively the greatest rate and extent of dry matter accumulation and subsequent mobilization in main stem. Genotypes with greater rates of dry matter accumulation and mobilization are exposed less to depressing effect of nitrogen deficiency than those with lower rates. Dry matter mobilized from all three segments of main stem in all genotypes examined in this trial increased in response to no application of N

Evaluation of Effect of Different Tillage Methods and Seed Rates on Yield and Yield Components of Rapeseed (Brassica napus) in Dry Land Condition

Abstract In order to study the effect of different tillage methods and seed rates on grain yield and yield components of rapeseed in dry land conditions, an experiment was performed from 2007-2008 season in Imamzadegafar Agriculture Education Center in Gachsaran. The experiment was set up as strip split plot based on randomized complete block design with 3 replications. Main plot factor was different tillage methods including: 1- no tillage 2- chisel plow + disk harrow 3- disk harrow + disk harrow 4- combinat 5- mold board + disk harrow. Sub plot factor was seed rates 5, 7 and 9 kg/ha. Properties of measurement were grain yield, yield components, number of branches, number of pod in bush, 1000 seed weight, harvest index, oil and protein content. The results showed that effect of combinat treatment on grain yield components was better than other treatments. Also amount 7 and 9 kg seed/ha was significantly different from 5 kg seed/ha. Maximum and minimum grain yield of 2957 and 1300 kg/ha produced by combinat with 7 kg seed/ha and no tillage with 5 kg seed/ha, respectively. Maximum and minimum oil content of %37.93 and %35.68 was obtained in combinat treatment with 5 kg seed/ha and moldboard plow with 9 kg seed/ha, respectively. Between yield components, number of branches and pod in bush showed maximum variablility and KTW, HI, oil and protein content had the minimum variation. In general, combinat treatment with 7 kg seed/ha was performed better than other treatments. Keywords: Rapeseed, Seed rate, Tillage method

Changes in Nutrient Content of Root and Grain of Wheat Cultivars Inoculated by Azospirillum and Mycorrhiza

Introduction: Providing the nutritional requirements of agricultural crops by non-chemical resources is a new approach in the organic farming that has attracted the attention of both the researchers and the consumers in recent years. Therefore, it is highly important to find new fertilizer resources that are both economically able to provide the nutritional needs of the crop plants and have no adverse effects on the consumers and the environment. Materials and Methods: With this approach, an experiment was conducted in the research station of Shahid Chamran University of Ahvaz, Iran in 2012-13. The experimental design was factorial based on randomized complete blocks design with three replications. The treatments including Mycorrhizal fungi in three levels (i.e. no use of strain; use of Glomus intraradices strain; and use of Glomus mosseae strain), bacteria Azospirillum lipoferum in two-levels (i.e. non-inoculated and inoculated) and wheat cultivars in three levels (i.e. Chamran; Dena; and Behrang). The measured parameters include the concentration of macronutrients (i.e. nitrogen, phosphorus and potassium) and some micronutrients (i.e. zinc, iron and manganese) in two part seed and the root of wheat. Results and Discussion: Surveying the elements content in the root and the grain indicated a significant and positive effect of the use the Azospirillum and Mycorrhiza to improve the concentration of the elements in wheat cultivars. However, the simultaneous use of these microorganisms led to an increase of the effects of their application on their assessed traits.Finally the highest concentration of N (2.21 present), P (0.50 present) and Fe (33.88 mg.kg-1) were observed in the grain; the highest concentration of K (0.93 present and 0.54 present) and Mn (43.11 and 23.63 mg.kg-1) were observed in the grain and root, respectively. Moreover, the highest concentration of Zn in the root (19.70 mg.kg-1) was obtained from inoculation of C.V Dena seeds with Azospirillum and the use of G. mosseae. Also, in the general case of Mycorrhiza fungi use (between 6 to 20 present) and seed inoculation with Azospirillum lipoferum (between 8 to 25 present), the improved nutrient content in the seeds as well as greatest impact of Mycorrhiza use is in increasing the content of the grain Zn (20 present) and the lowest effect of Mycorrhiza using is in increasing the nitrogen content in seed (6 percent). Considering the elements content in the grain, the use of bacteria also showed that the greatest impact on increasing the use of bacteria Azospirillum lipoferum is in increasing the iron content in seeds (25 present) and the least impact of the use of Azospirillum lipoferum is in increasing the seed’s manganese (8 present). Moreover, the use of Mycorrhiza fungi (between 7 and 23 present) and seed inoculation with Azospirillum lipoferum (4 to 16 present) improved the contents of nutrients in wheat roots compared with the control group. Here, too, the greatest impact for Mycorrhiza application was in increasing the content of the Zn in the root (23 present) and the lowest effect of Mycorrhiza application was in increasing the potassium content in the root (7 percent). Moreover, considering the elements content in the roots in the case of being treated with Azospirillum lipoferum, the results showed that upon increasing the use of bacteria, the greatest impact of Azospirillum lipoferum in increasing elements content in the roots was an increased iron content in the root (16 present) and the minimum effect of the bactericidal application was in increasing the potassium root (4 present). Comparing the two species of Mycorrhizal fungi that have been used in the experiment, although application Glomus intraradices showed satisfactory results, the use of the species Glomus mosseae to increase the content of the element in seeds and roots has had a greater role. Moreover, the combined effects of these microorganisms have not only had an antagonistic effect of reducing the amount of content, they have also been more effective than being applied separately (between 7 and 12 present). Conclusion: Generally associated with most of the measured elements, the treatment of seed inoculation with Azospirillum lipoferum and usage of Glomus mosseae in Dena cultivar that was a durum wheat, showed the highest concentration of the mentioned elements in the roots and seeds. Probably this has been due to the smaller grains in Dena than the other cultivars, which led to an increase in the ratio of the elements in the grain. Therefore, it seems that the use of the biofertilizers can be the perfect solution to eliminate the nutritional requirements of wheat. Moreover, it has the very important effect of the enrichment of this crucial product in the people’s dietary patterns in this country with the required elements. Keywords: Azospirillum, Nutrition, Wheat, Root, Elements concentration, Mycorrhiz

Using boundary line analysis to assess the on-farm crop yield gap of wheat

Food security is one of the most important challenges facing human kind. A very promising approach to solve the problem is closing the yield gap, i.e. the difference between farmer's and potential yield. A 'complete yield gap assessment method' must provide information regarding potential yield, actual yield and yield gap, the causes of the gap and their importance. The objective of this study was to indicate how boundary line analysis (BLA) could be applied to such an assessment. BLA was only applied to crop management practices/inputs, e.g. sowing date and rate and fertilizer applications. The data were gathered from about 700 wheat farms in Golestan province, one of the major wheat producing regions in Iran, during two growing seasons of 2013-2014 and 2014-2015. Wheat production in Golestan province can be divided into three production situations according to agro- and geo-climatology criteria: these are 'irrigated or high-rainfall', 'high-yield rainfed', and low-yield rainfed'. Boundary lines were fitted to the edge of the data cloud of crop yield versus management variables using data from each of the three wheat production situations in the province. Actual farmers' yields were 3900 kg ha(-1) for irrigated, 4000 kg he' for high-yield rainfed and 2000 kg ha(-1) for low-yield-rainfed situations; BLA indicated that potential yields (the highest yields obtained by farmers in the sample) were 6900,5800 and 3900 kg ha(-1) for each situation, respectively. The corresponding yield gaps were high at 42%, 31% and 50%. Using BLA it was possible to determine the optimal sowing date, seeding rate, frequency and amount of nitrogen fertilizer applied, amount of nitrogen top-dressing, amount of phosphorus and potassium fertilizers and irrigation frequency. The percentage of farmers who cultivated outside of the optimal levels was also identified and was used to determine the importance of each management factor in yield gap. It was concluded that BLA as applied in the study, was a cheap and simple method which, without the need for expensive experimentation, was able to detect yield gaps and their causes in a region. The method can be used effectively in countries/regions where important yield gaps exist