International Journal of Plant Production
Volume:11 Issue: 2, Apr 2017

A field experiment was carried out to investigate the effects of varying nitrogen (N) supply and irrigation methods on the root growth and distribution of maize (Zea mays L.) in Wuwei, northwest China in 2011 and 2012. The irrigation treatments included alternate furrow irrigation (AI), fixed furrow irrigation (FI) and conventional furrow irrigation (CI). The N supply treatments included alternate N supply (AN), fixed N supply (FN) and conventional N supply (CN), were applied at each irrigation method. The root growth across the plant row was measured in 0-100 cm soil profile (20 cm as an interval) at maturity. The results showed that root distribution of two sides of the row was uniform for AI or CI coupled with CN or AN. Root length density (RLD) in 0-40 cm soil depth was significantly increased by AI compared to other irrigation methods while decreased by FN compared to other N supply treatments. Though RLD decreased more with soil layer deepening under AI, RLD in 60-100 cm soil depth in AI treatment was still larger than that in CI and FI treatments. In general, total fine root (diametersurface area, and grain yield of maize were significantly increased by AI coupled with CN or AN when compared to other treatments. These results indicate that alternate partial root zone irrigation coupled with conventional or alternate nitrogen supply is useful to improve the root growth and grain yield of maize in the arid area.

The impact of chemical desiccation on yield showed contrasting results depending on seed moisture content at the time of application. Its effects on seed deterioration are still unknown and could be modified by seed composition. Objectives were to evaluate the impact of chemical desiccation on: i) hybrid sunflower seed yield and composition at harvest time, ii) seed deterioration during long-term storage and iii) the relationship between seeds deterioration and oil or oleic acid content. Six hybrids including low, mid and high oleic were evaluated in three experiments. Two treatments were applied on female lines at 27-30% seed moisture: (i) spraying with Paraquat and (ii) detaching heads with a knife. Control remained in the field until 10% seed moisture. Seeds were stored during 19 months under room and cold chamber conditions. Yield, number of seeds and hybrid seed composition (thousand seed weight, kernel percentage, oil and acid oleic content) were determined. Seed deterioration during storage was analyzed by germination and vigour. Paraquat advanced harvest by 35-43 days, without affecting yield or seed composition. During storage the germination of Paraquat treatments remained above that of control, without differences between storage conditions, while vigour remained above control only in cold chamber, for low oleic hybrids. Associations between deterioration (germination and vigour) and oil or oleic acid content, were not significant. Desiccation with Paraquat allows advanced harvest without yield losses or modifications in seed composition. The deterioration of desiccated seeds was lower and independent from oil and oleic acid content.

In order to study the effects of different irrigation regimes and plant density on yield component and protein concentration and crop water stress index (CWSI), under research field conditions a split plot arrangement was conducted in completely randomized block design during two years. The first factor of variables was the effects of 4 irrigation levels 120% ( 1), 100% (I2), 80% (I3) and 60% (I4) of Standard evapotranspiration and the second factor was the spacing of 5 cm (D1), 10 cm (D2) and 15 cm (D3) between plants within a row. Results indicate that the number of pods in each plant and the grains in each pod decreased when density increased, but the hundred-grains-weight and the height of bean plants increased. When irrigation increased, various increases were observed in the yield, the number of pods in each plant, the grains in each pod, the hundred-grains-weight and the height of bean plants, but the grain protein decreased. Protein concentration increased with more severe water deficit in the soil. The protein concentration directly correlated with total irrigation water during the growing season (TI) and the exponential equation P=33* e -4E-04TI can be used for protein concentration prediction. The effect of the irrigation water was significant and CWSI increased with increased soil water deficit. The effect of the density for CWSI was not significant. Grain yield (GY) directly correlated with CWSI and the exponential equation, GY=696.2(CWSI)-0.51 can be used for the prediction of grain yield. The CWSI value is useful for evaluating crop water stress in beans and thus it could be useful in timing the irrigation. Results of this research indicate that yield components such as height of bean plant, the number of pods in each plant and the number of grains in each pod were significantly different by applying the different irrigation strategies at the three different lengths of plant spacing within a row.

The relationship between arbuscular mycorrhizal fungi (AMF) and their associated bacteria can be has great importance for sustainable agriculture especially in the case of highly mycorrhizal plants such as linseed. To evaluate the possible effect of AMF in association with phosphate solubilizing bacteria (PSB) on linseed plants, a 2-yr factorial experiment was conducted based on a randomized complete block design with three replications at Urmia University, Urmia, Iran (37° 39′ 24.82″ N 44° 58′ 12.42″ E). The treatments included two AMF species (Glomus mosseae, G. intraradices and non-mycorrhizal control), PSB (Pseudomonas putida P13 and non-inoculated control) and various irrigation regimes (irrigation after 60, 120 and 180 mm of evaporation from Class A pan). A significant increase in mycorrhizal linseed plants yield indicated the effectiveness of the two AMF species more than bacterial inoculation. The cumulative (second year) soil spores were maximally observed in mycorrhizal (single AMF and dually inoculation) treatments. The reduction in bacterial population was found with an increase in water deficit. Dual infections caused an increase in leaf P content more than the one in PSB and AMF inoculations. Drought stress-induced yield reduction in seed and in oil was significantly compensated by mycorrhizal symbiosis for all irrigation levels. We found over 25% increase for seed yield and 30% for oil yield in mycorrhizal plants as well as co inoculated plants. The yields improvements in mycorrhizal treatments (single and dually inoculated) leading to the highest water use efficiency.

The aim of the study was to determine the biomass, abundance and species composition of weeds, as well as macroelement uptake in potato weeded using mechanical, mechanical– chemical and mechanical control combined with the sowing of living mulches of white mustard, common vetch, Persian clover and tansy phacelia. Abundance and biomass of the weeds was the most effectively limited by the mechanical treatments. The effectiveness of mechanical treatments in weed biomass reduction was 2.5–fold lower. The mechanical treatments more effectively limited the number of monocotyledonous than dicotyledonous weeds. Living mulches increased the efficiency of mechanical weeding by affecting both weed biomass development and weeds abundance. The living mulch that most effectively limited the growth of weed biomass was white mustard, while vetch was effective to reduce of the number of monocotyledonous weed and Persian clover for dicotyledonous weeds. The most frequently occurring weed species were Galinsoga parviflora, Chenopodium album and Echinochloa crus-galli. The share of N accumulated in the biomass of neighboring plants constituted from 5% to 34%, P from 6% to 38%, K from 5% to 36%, Ca from 27% to 190% and Mg from 12% to 55% of the amount of these nutrients absorbed by potato plants. Mechanical treatments plus living mulches, especially Persian clover, may be useful in organic cropping systems due to their effectiveness at reducing weed abundance and biomass and relatively low nutrient uptake compared with weeds.

This research aimed to determine the effects of different cover crops and application of bio-fertilizer on dynamic of nitrogen in the soil and sweet maize yield. Also, we evaluated the effect of fall–winter species (common vetch, field pea, winter oats, fodder kale) and a mixture of vetch and field pea with oats used as cover crops, as such as dead organic mulch and traditional variant, without coverage on biomass, chlorophyll and protein content in leaves and grain of main crop. Biomass production and N uptake by cover crops ranged from 4.25 to 90.20 kg ha-1 and from 0.34 to 133.80 kg ha-1 N, respectively, depending on cover crop type. At harvest soil nitrate content in treatments with cover crops was 50-90% lower than in the control, reducing spring N leaching risk. Residual mineral N significantly increased with application of microbiological fertilizer. The chlorophyll content of the main crop was significantly lower in treatments without cover crops. Consequently, sweet maize yield was the highest in fodder kale and field pea (7263.83 and 7177.27 kg ha-1) treatments, but the smallest in winter oat and common vetch (6802.47 and 6184.14 kg ha-1). In terms of all investigated traits, particularly grain yield, cover crops and microbiological fertilizer expressed more efficiency in the dry year. It could be concluded that N content should be controlled effectively by sowing main crops after planting of cover crops in biological farming systems in a semiarid region.

Accurate estimation of leaf stomatal conductance (gs) is important in predicting carbon and water cycles of terrestrial ecosystem. To estimate gs on field-grown soybean and maize under water-stressed condition accurately, a modified optimal stomatal conductance (OSCM) model was established based on the relationship between marginal water cost of carbon gain and soil water content by introducing a water stress factor (f(θv)). f(θv) had same form with that in Jarvis and Ball-Berry-Leuning (BBL) models. The OSCM model was evaluated and compared with the original optimal stomatal conductance (OSC), Jarvis and BBL models by comparing observed and estimated gs of three-year data on soybean and four-year data on maize in an arid region of northwest China. Results show that the OSCM and OSC models were more steady and accurate than the Jarvis and BBL models for estimating gs on soybean and maize at the different years. Moreover, the OSCM model performed better than the OSC model because of considering the effect of water stress. Compared with the OSC, Jarvis and BBL models, the OSCM model improved the accuracy of estimating gs on soybean and maize on average by 7%, 25% and 35% and reduced the RMSE by 19%, 56% and 43%, respectively. As for estimating diurnal change of gs on soybean and maize under both well-watered and water-stressed conditions, the OSCM model also performed better than the OSC, Jarvis and BBL models. Under water-stressed condition, only the OSCM model is recommended due to its high accuracy, conservative and accessible parameter, which can provide a more accurate and convenient tool in predicting water and carbon fluxes of terrestrial ecosystem in the arid area.

Clustering was used to divide dryland farming areas in western Iran into homogeneous sub-regions to identify dryland farming potential, considering drought impacts. Clustering utilized eight algorithms/four indices to detect optimal number of clusters. Ward’s algorithm validated by Silhouette index, produced the best result by detecting 7 dryland farming clusters. Based on similar P/ETo values, four sub-regions were recognized among 7 clusters. Northwestern sub-region was ranked first, followed by central, northeastern and southern sub-regions. Drought impact analysis led to 6 optimal clusters by Ward’s algorithm, validated by Silhouette index. Ranking criteria utilized drought characteristics, obtained from 3- to 12- months SPI analysis. Northwestern sub-region and parts of central sub-region, with respectively first and second rankings for dryland farming, are also least affected by droughts. Areas in central sub-region with good dryland farming potential can be strongly impacted by droughts. Northeastern and southern sub-regions respectively ranked third and fourth for dryland farming, were severely affected by droughts. In conclusion, areas with highest dryland farming potential were impacted minimally by drought, while areas with lowest potential were strongly affected by droughts. However, sub-regions with good dryland farming potential were be severely influenced by drought. Therefore, drought analysis should be considered for dryland farming management.

Irrigation scheduling is important in irrigation water management. In this study, full (FI), deficit (DI) and partial root drying (PRD) irrigation strategies were applied in Agria and Ramos potato cultivars. Canopy temperature (CT) and leaf water potential (LWP) were assessed as the potential tools for irrigation scheduling during the vegetative and productive growth stages. LWP varied between ca. -1.4 and -1.6 MPa and was not significantly different between FI, DI and PRD irrigation treatments. The LWP and CT values were not significant between the two potato cultivars during the measurements, but CT was frequently significant between the irrigation treatments such that the PRD treatments were significantly 5 and 2 oC warmer than FI and DI treatments, respectively. Higher CT in PRD caused significant yield penalty such that DI and FI produced almost two times higher fresh tuber yield. Analysis revealed that CT had significantly higher correlation (r=0.66) with water productivity (weight of fresh tuber yield divided by volume of applied irrigation water) than LWP, which its correlation was not significant (r=0.40). This showed that crop water productivity could be better controlled by CT. Moreover, it was realized that the seven-day irrigation interval was far longer than required and potatoes in all irrigation treatments were under water stress, especially in PRD, that might partially explain the 50% yield penalty of PRD compared to DI. The reason was that due to high atmospheric demand, soil water in the wet part of the root system would be completely depleted earlier by the time of next irrigation event. Conclusively, the CT is recommended as a more reliable crop water status and irrigation scheduling indicator than LWP in response to different water-saving irrigation managements.