Late Planting Date Research Articles

Comparison of three methods for delineating management zones for site-specific crop management

The goal of this study was to evaluate different strategies for defining homogeneous zones, and to verify their usefulness by comparing soil moisture contents and crop yields. Data were obtained from a field experiment near General Pico, La Pampa, Argentina, with a sampling grid of 598 points. Soil texture, organic matter, available phosphorus, pH, and electrical conductivity were determined. Altimetry was obtained by a GPS (Garmin 19X). Corn yields and available soil moisture contents were determined in a 184 point grid. Treatments were early and late planting date, and control and 100kgNha−1. MULTISPATI-PCA was used to carry out for multivariate spatial analyses of soil attributes. The synthetic variables (sPC) were analyzed, mapped and used for determination of homogeneous zones by three strategies: S1-natural rupture method on sPC1, S2-Fuzzy k-means cluster analysis on soil variables and S3-Fuzzy k-means cluster analysis on all sPC. Zones were compared for means of soil variables, available soil water and maize yields. The three tested statistical strategies divided the field in a very similar manner when the minimum number of zones was considered, with coincidence in the classification of 98% of the sampled grid points. The different strategies resulted in different number of zones with different characteristics. The choice of the method depends on the objectives for determination of management zones. In our case, for fertilization management zonification might prioritize the differentiation of OM and available P contents and use S3, while if water was the main limiting factor, the management zones would be two according to S1 or S2, responding to textural and altimetry differences.

Calibration and testing of AquaCrop for selected sorghum genotypes

Predicting yield response to water is important in rainfed agriculture. The objective of this study was to calibrate and test AquaCrop for simulating yield of 3 sorghum genotypes (PAN8816, a hybrid; Macia, an open-pollinated variety; and Ujiba, a landrace) grown during the 2013/14 and 2014/15 planting seasons (early, optimal and late planting dates). Variables considered during model evaluation included canopy cover (CC), biomass (B) and yield (Y). The model was able to simulate CC ( R 2 ≥ 0.710; root mean square error (RMSE) ≤ 22.73%; Willmott’s d-index ( d ) ≥ 0.998), biomass accumulation ( R 2 ≥ 0.900; RMSE ≤ 10.45%; d ≥ 0.850), harvest index ( R 2 ≥ 0.902; RMSE ≤ 7.17%; d ≥ 0.987) and yield ( R 2 ≥ 0.945; RMSE ≤ 3.53%; d ≥ 0.783) well for all genotypes and planting dates after calibration. AquaCrop over-estimated biomass and crop yield. The relatively good simulations produced by the minimum data input calibration confirm AquaCrop’s simplicity and suitability for use in places where extensive datasets may be unavailable. Biomass and yield overestimation resulting from the use of the minimum data input calibration suggests that other parameters (water productivity, canopy sensitivity to water stress and water stress coefficient) are required to improve canopy and yield predictions for sorghum genotypes. Keywords: modelling, parameterization, minimum data input calibration, sorghum, water availability

Productivity of non-heading Chinese cabbage (Brassica rapa subsp. chinensis) under different agronomic management factors

Productivity of non-heading Chinese cabbage (Brassica rapa L. subsp. chinensis) was evaluated at Roodeplaat over two winter seasons (2012 and 2013). Agronomic factors considered were plant density, nitrogen level, irrigation frequency and planting date. Irrigating thrice or once a week with 50 kg N ha−1 at 50 000 plants ha−1 produced tall plants with large leaf area (p < 0.05). Irrigating once a week combined with 100 kg N ha−1 increased leaf chlorophyll content. Application of 50 and 100 kg N ha−1 significantly (p < 0.05) increased leaf number, plant height, chlorophyll fluorescence and yield for early and late planting dates. Irrigating three times a week led to significant (p < 0.05) increase in plant height and yield for late and early planting. Higher leaf quality parameters (chlorophyll content index and leaf area index) suggested that non-heading Chinese cabbage could be grown at densities of 50 000 plants ha−1. However, plant density of 133 333 plants ha−1 resulted in significantly (p < 0.05) higher yield in terms of leaf number and fresh mass for late planting in both seasons. Early planting, application of 50 kg N ha−1, irrigating three times a week and a plant population of 50 000 plants ha−1 is recommended for non-heading Chinese cabbage.

Water use of sorghum (&lt;i&gt;Sorghum bicolor&lt;/i&gt; L. Moench) in response to varying planting dates evaluated under rainfed conditions

It is vital to understand how rainfall onset, amount and distribution between planting dates affect sorghum yield and water use, in order to aid planting date and cultivar selection. This study investigated morphological, physiological, phenological, yield and water use characteristics of different sorghum genotypes in response to different planting dates under rainfed conditions. Four genotypes (PAN8816 [hybrid], Macia [open-pollinated variety, OPV], Ujiba and IsiZulu [both landraces]) were planted on 3 planting dates (early, optimal, and late) in a split-plot design, with planting dates as the main factor. Low soil water at the optimal planting date was associated with delayed crop establishment and low final emergence. Sorghum genotypes adapted to low and irregular rainfall at the late planting date through low leaf number, canopy cover, chlorophyll content index and stomatal conductance, and hastened phenological development. This resulted in low biomass and grain yields. Landraces exhibited grain yield stability across planting dates, whilst OPV and hybrid genotypes significantly reduced grain yield in response to low water availability when planted late. Biomass and grain yield water use efficiency (WUE) were highest at optimal planting date (30.5 and 9.2 kg∙ha -1 ·mm -1 ), relative to late (23.1 and 8.7 kg·ha -1 ·mm -1 ), and early planting dates (25.2 and 8.3 kg·ha -1 ·mm -1 ). For PAN8816 and Macia, biomass and grain WUE decreased in response to low soil water content, and irregular and disproportionate rainfall experienced during the late planting date. By contrast, biomass and grain WUE for Ujiba and IsiZulu improved with decreasing rainfall. PAN8816 is recommended when planting under low soil water availability to maximize crop stand. Cultivation of Macia is recommended under optimal conditions. Ujiba and IsiZulu landraces are recommended for low rainfall areas with highly variable rainfall. Repetition or modelling of genotype responses across environments different from Ukulinga is required for thorough water use characterisation of these genotypes. Keywords : planting dates, water use efficiency, rainfall variability, cultivar selection, landraces and improved sorghum varieties

Modeling the Potential Impact of Climate Change on Cotton (Gossypium hirsutum) Production in Northeastern Semi-Arid Afar and Western Tigray Regions of Ethiopia

Cotton (Gossypium hirsutum) is a globally important fiber plant. Impact of climate change and variability is already being felt in Ethiopia in the form of higher temperature, erratic nature of rains (spatially and temporally), floods and drought. The aim of this study was to characterize the climate of the study areas, analyze the impact of climate change on cotton production and to recommend suitable adaptation strategies for cotton production under changing climate at Amibara, Dansha and Kebabo areas of Ethiopia. Historical climate data during 1980-2010, were collected from National Meteorological Agency and National aeronautical space administration while soil and cotton experimental data of the study areas were collected from respective agricultural research center. DSSATV4.6 model was calibrated and evaluated to assess the possible impact of climate change on cotton yield under the baseline and future climate. Model performance was assessed statistically by using quantitative statistical indicators: coefficient of de-term ination (R2), root mean square error (RMSE) and index of agreement (IA). In order to estimate the level of climate change impact (rainfall and temperature) on cotton production for the study areas, two Representative path ways as a threetime segment: Near-term i.e., 2010-2039, Mid-term i.e., 2040-2069) and End-term i.e., 2070-2099 using the coupled atmosphere-ocean HadGEM2-ES GCMs model. Time series anomaly plots for temperature showed that the mean temperature over Amibara, Dansha and Kebabo has increased by about 0.5 to-2ºC, 0.5 to 1.65oC and 0.5 to 1.5oC and rainfall showed slight variability in start and end of season during the period of 1980-2010. The projected temperature and rainfall pattern shows that an overall increasing trend in annual temperature and significant variation of monthly and seasonal rainfall from the historical period of time. The rainfall varies between-1.6 to 3.3%,-0.7 to 3.8% and-0.8 to 3.3% at Amibara, Dansha and Kebabo respectively. Climate change analysis indicated a strong influence of temperature on cotton production in Amibara and Dansha sites and yield will be substantially decreased on average by 12% to 13% with projected increasing temperature and erratic nature of rainfall. Projected model simulations predict that climate change will shift planting dates towards late planting (May 15 and July 15) for the period of 2010-2099 at Amibara and Dansha while for Kebabo site early planting June 15 is preferable. In general cotton yield, will decrease but, late planting date and further research on different agronomic management practices will result in increased yield for Amibara and Dansha.

Growth and Development of Green pepper (&lt;i&gt; Capsicum annuum&lt;/i&gt; L) as Influenced by Planting Dates and Fertilizer Application in Owo, South West Nigeria

Field experiments were conducted in 2014 under rainfed and irrigation cropping to evaluate/monitor the influence of fertilizer application and planting dates on the growth and yield of green pepper in Owo, South West Nigeria towards its production year round. Treatment evaluated consisted of two varieties of sweet pepper (California wonder and Tattasai dan-garko), three fertilizer types (organic, urea and organomineral) and four planting dates in each season (2-April; 12-April; 22-April and 2-May for early season and 22-Sept.; 01-Oct; 11-Oct and 23-Oct for the late season planting).These were factorially combined in a randomized complete block design (RCBD), and replicated three times. Compared to control, OMG, ORF and Urea fertilizers significantly (P < 0.05) increase both the growth and yield parameters. The growth and yield of the crop was favoured at the late planting date when the soil moisture was augmented with the supplementary irrigation and on the other hand, the rainfed cropping favours production of higher biomass, thus reducing the total harvested yield .The 02-May and 23-Oct planting dates and the application of OGM recorded the best growth and yield attributes. Among the varieties, California wonder exhibited adaptable superior characteristics in terms of number of fruits (59.59) fruit weight (6.68g) harvestable yield (2480.82kg/ha). The interaction effect showed that variety California wonder transplanted on 23-Oct recorded more improvement in the form of highest leaf area (8.79 cm2), maximum number of fruits/ plant, fruit weight (86.93 g) and fruit yield (854.69 g/plant and 23.08 t/ha). The results established that 23-Oct is ideal for bell pepper planting and the variety California wonder is the most stable performing variety with respect to the different planting dates

Production potential of barley varieties as affected by time of sowing under changing climatic conditions in semi-arid eastern plain zone of Rajasthan

An experiment was conducted consecutively for three years from rabi 2012–13 to 2014–15 at Rajasthan Agricultural Research Institute, Durgapura, Jaipur to find out the effect of dates of sowing on two and six-rowed barley varieties under changing climatic conditions in semi-arid eastern plain zone of Rajasthan. The experiment was conducted with four dates of sowing i. e. 26th Oct.-5th Nov. (D1), 6th-15th Nov. (D2), 16th-25th Nov. (D3) and 26th Nov.-5th Dec. (D4) and four barley varieties i. e. BH 902 & RD 2552 (six-rowed) and DWRUB 52 & RD 2668 (two-rowed). These treatment combinations were tested under split plot design with three replications. The data indicated that significantly higher grain and straw yields were obtained with early planting date i. e. 6th to 15th Nov. (D2) followed by 26th Oct. to 5th Nov. (D1) than that of late planting dates for all genotypes during all the years. Effective tillers/sq. m, 1000-grain weight and grains/spike were also higher in early planting date i. e. 6th to 15 Nov. (D2) than that of late planting date during all the years. Amongst the varieties, BH 902 & RD 2552 (six-rowed barley) gave significantly higher grain and straw yields during all the years as compared to DWRUB 64 & RD 2668 (two-rowed barley). Effective tillers/sq. m and grains/spike were also higher, while 1000grain weight was lower with six-rowed barley during all the years as compared to tworowed barley.

Efficacy of planting date adjustment as a cultivation strategy to cope with drought stress and increase rainfed maize yield and water-use efficiency

Given the frequent drought pressure caused by the unpredictable and limited precipitation concurrent with global climate change, highly efficient cultivation technologies have been increasingly recognized by various levels of scientific communities. Understanding plant–environment relationships in rainfed dry land may help maximize crop productivity while improving water utilization of farmland. Field experiments were conducted in 2012–2014 at the Dryland Maize Experimental Station of the Northwest A&F University, China to determine the effects of possible drought stress and the environmental factors involved during sowing at different sowing dates on maize vegetative growth and grain yield (Zea mays L.), as well as water-use efficiency (WUE=grain yield per unit of seasonal evapotranspiration). Six planting date (PD) treatments with sowing performed for 6 days from April 10 to May 10 were designed. Results showed that the maize growth period was shortened with the postponement of planting time. The vegetative growth stage and the overlapping stages of vegetative and reproductive growth varied by 4–19 days among various PD practices. However, the reproductive growth stage duration was relatively stable and varied by 3–5 days only among the different PD practices. Within a certain time range, dry matter production per plant did not obviously change across the different PD treatments. However, the dry matter accumulation in the ear after flowering, the yield, and the WUE in the treatments under appropriate PDs (April 16–April 28) were 2.2%–28.8%, 2.3%–24.7%, and 6.6%–15.2% higher, respectively, than those in the early or delayed PDs. These findings resulted from the changes in soil water content with PD adjustment. Yield was highly correlated to the soil moisture content during PD, the rainfall before silking, the effective accumulated temperature after silking, and the sunshine hours after silking. Moreover, the thousand-grain weight was highly correlated with the sunshine hours after silking. In the early PDs, the main factor that affected maize yield was the low content of soil moisture, which generated low effective ear number per unit area and seedling emergence ratio. In the late PDs, the main factors that influenced maize yield were the low effective accumulated temperature and the short sunshine hours during the reproductive growth stage, which produced less dry matter accumulation after silking and lower thousand-grain weight. Under suitable sowing time, the actual harvest ear number per hectare and dry matter accumulation of female ear after silking increased. Similarly, the maize yield and WUE increased. By considering the ecological factors and study results, we recommend that the most suitable sowing time for maize should be determined on the basis of the soil moisture content before April 28. As such, we can effectively achieve high yield and avoid drought in the study region. Overall, the results can provide effective cultivation techniques to prevent drought stress in spring maize in the present agro-ecosystem of northern China and other similar areas.

Effect of Nano-Fertilizer (Lithovit) and Potassium on Leaves Chemical Composition of Egyptian Cotton Under Different Planting Dates.

Two field experiments were carried out at El-Gemmeiza Agricultural Research Station, El-Gharbia Governorate in 2014 and 2015 seasons, to study the effect of nano-fertilizer (Lithovit) rates (0, 2.5, 5 and 7.5 g/l) and foliar potassium fertilizer (in the form of Potasin-P) rates (2.5, 5 and 7.5 cm3/l) under three planting dates (8 April, 8 May and 8 June) on leaves chemical composition of the Egyptian cotton (Gossypium barbadense L.), cultivar Giza 86. Cotton plants were foliar sprayed with Lithovit and Potasin-P at 45 and 60; 46 and 61 days after planting, respectively. Leaves N, P, K, chlorophyll a, b, total chlorophyll, carotenoids and total carbohydrates contents were significantly affected by planting date in both seasons, in favour of early planting date (8 April) compared to medium and late planting dates (8 May and 8 June). Delaying planting date significantly increased leaf proline content and leaf peroxidase activity which indicate the presence of heat stress effect on the plant.Leaves N, chlorophyll a, b, total chlorophyll, carotenoids and total carbohydrates contents were significantly affected by rates of Potasin-P in both seasons, in favour of the medium rate of Potasin-P (5cm3/l). While, leaves P and K contents were significantly increased by using the high rate of Potasin-P (7.5cm3/l). The medium rate of Potasin-P (5cm3/l) significantly decreased leaf proline content and peroxidase activity which indicate favorable plant conditions.Leaves N, P, K, chlorophyll a, b, total chlorophyll, carotenoids and total carbohydrates contents were significantly increased by each increment of nano-fertilizer (Lithovit). The inverse was true in leaf proline content and peroxidase activity. The decrease in these traits induced favorable plant conditions and reflected on reduce environmental stress effect.The second order interaction had a significant effect on all studied chemical composition of leaves. Cotton plants sown on 8 April and sprayed with 5cm3 Potasin-P /l and 7.5 g Lithovit/l recorded the highest values of N, P, K, chlorophyll a, b, total chlorophyll, carotenoids and total carbohydrates content in leaves. In the contrary, this interaction recorded the lowest values of leaf proline content and peroxidase activity which induced favorable plant conditions and reflect on reduce environmental stress effect. It can be concluded that the mentioned interaction was the recommended treatment for optimum chemical composition of cotton leaves under experimental conditions.

Effects of late planting and shading on sucrose metabolism in cotton fiber

Effects of cool temperature due to late planting and low light due to shading on sucrose metabolism in cotton fiber were investigated with two cotton cultivars (Kemian 1, cool temperature-tolerant and Sumian 15, cool temperature-sensitive) at two planting dates (the optimized planting date 25 April and the late planting date 10 June) along with two shading levels of crop relative light rate (CRLR) 100% and 60% in 2010 and 2011. Compared with the optimized planting date with CRLR 100% (OPD), the acid invertase (AI) activity was little affected in the optimized planting date with CRLR 60% (OPD-CRLR 60%). The sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) activities were decreased, which would reduce sucrose degradation and recycle, hindering the synthesis of cellulose. However, the sucrose concentration was decreased, which might be because of lower sucrose import from the leaf. The transcript levels of sucrose synthase gene (Susy) and sucrose phosphate synthase gene (SPS) isoforms were decreased. Comparison between the two cultivars, SPS1 was the largest down-regulated isoform in Kemian 1, but SPS2 was the largest down-regulated isoform in Sumian 15. Also, the SPS activity was more sensitive to low light for Kemian 1 than Sumian 15. Although SuSy and AI activities were much higher in the late planting date with CRLR 100% (LPD) than OPD, sucrose concentration was still high. Therefore, a lot of sucrose could not be fluently used in cellulose synthesis, leading to the decrease of cellulose concentration. The transcript levels of the three SPS isoforms increased for both cultivars. The expressions of SusyA, SusyB, and SusyC were increased for Kemian 1, but the expressions of SusyD, SusyA, SusyB, and SusyC were significantly decreased for Sumian 15. In the late planting date with CRLR 60%, no interaction effect between cool temperature and low light was observed in the concentrations of cellulose and sucrose, the activities of SPS and AI and the expression of SPS3, but was found in the transcript levels of SusyB and SPS2 for both cultivars. Also, the interaction effect was observed in the transcript levels of SusyA, SusyC, SusyD and SPS1 in Sumian 15, but was not found in Kemian 1.

The Evaluation of Exogenous Application of Salicylic Acid on Physiological Characteristics, Proline and Essential Oil Content of Chamomile (Matricaria chamomilla L.) under Normal and Heat Stress Conditions

The objective of this study was to investigate the effect of exogenous application of salicylic acid concentrations on the physiological and biochemical traits and essential oil content of chamomile under normal and heat stress conditions as induced by delayed sowing. The experiments were conducted during 2011–2012 as a factorial using a randomized complete block design with three replications, in a very hot region. The factors included five salicylic acid concentrations (0 (control), 1, 10, 25 and 100 mg·L−1) and three chamomile cultivars (Bushehr, Bona, Bodegold). The seeds of chamomile were sown on two different sowing dates including an optimum planting date and a late planting date. The physiological traits (plant height, capitol diameter, 1000 grain weight, fresh and dried flower weight), total chlorophyll, proline and essential oil content were investigated. Analysis of variance showed that the effect of the environmental conditions (normal and heat stress) was significant on all physiological and biochemical traits with the exception of the essential oil content. The heat stress decreased physiological traits and total chlorophyll in comparison with the normal conditions but it had no significant effect on the essential oil content. Findings indicated that the application of exogenous salicylic acid improves essential oil content in chamomile cultivars under environmental heat stress conditions.

Country-Level Bio-Economic Modeling of Agricultural Technologies to Enhance Wheat-Based Systems Productivity in the Dry Areas

&lt;p&gt;Conservation Agriculture (CA) have a large potential for enhancing cereal yields in the semi-arid areas through better management of soil moisture. The objective of the current paper is to quantify, at national level, the impact of CA adoption in wheat-based agricultural systems in Syria. A country-level bio-economic approach was used for this purpose. Different CA technical packages (TPs) were first developed and simulated through APSIM crop modeling software, in order to estimate the long-term yields of wheat under different CA TPs for the period 2015-2039. The considered CA packages are a combination of zero-tillage, mulching, raised bed, fertilizer doses, and planting dates. The simulated yields are then introduced into IMPACT model while assuming that TPs will be adopted on 35% of the wheat areas in the countries. Results show that the comparative advantages of CA TPs on overcoming the effect of climate change will only be significant after 2030. In 2039, the effect of different TPs on average wheat yields in Syria will be 4% to 12% (depending on the TP) higher than the average yields under climate change and no CA technology adoption. These yield enhancements may reduce the wheat trade deficit with 30 up to 140%, also depending on the technical package. The combination of mulching techniques, together with average nitrogen dose of 30kg/ha, and late planting date of wheat provides the best prospective for the wheat sector in Syria.&lt;/p&gt;

Cover Crop Impact on Weed Dynamics in an Organic Dry Bean System

Weed suppression is one possible benefit of including cover crops in crop rotations. The late spring planting date of dry beans allows for more growth of cover crops in the spring. We assessed the influence of cover crops on weed dynamics in organic dry beans and weed seed persistence. Medium red clover, oilseed radish, and cereal rye were planted the year before dry beans; a no-cover-crop control was also included. After cover-crop incorporation, common lambsquarters, giant foxtail, and velvetleaf seeds were buried in the red clover, cereal rye, and no-cover control treatments and then retrieved 0, 1, 2, 4, 6, and 12 mo after cover-crop incorporation. Dry beans were planted in June and weed emergence and biomass measured. Eleven or more site-years of data were collected for each cover-crop treatment between 2011 and 2013, allowing for structural equation modeling (SEM), in addition to traditional analyses. Cereal rye residue increased giant foxtail and velvetleaf seed persistence by up to 12%; red clover decreased common lambsquarters seed persistence by 22% in 1 of 2 yr relative to the no-cover-crop control. Oilseed radish and incorporated cereal rye rarely reduced weed densities. When red clover biomass exceeded 5 Mg ha−1, soil inorganic N was often higher (5 of 6 site-years), as were weed density and biomass (5 and 4 of 12 main site sample times, respectively). Using SEM, we identified one causal relationship between cover-crop N content and weed biomass at the first flower stage (R1), as mediated through soil N at the time of dry bean planting and at the stage with two fully expanded trifoliates. Increasing cover-crop C : N ratios directly reduced weed biomass at R1, not mediated through changes in soil N. Cover crops that make a significant contribution to soil N may also stimulate weed emergence and growth.

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Genotype by environment interaction results in significant differences in the performance of cultivars when tested in diverse environments. Nine improved cowpea (Vigna unguiculata (L.) Walp) cultivars obtained from International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and a local check were evaluated for growth, reproductive and grain yield components in a non-traditional cowpea growing region of south eastern Nigeria with the aim of identifying high yielding genotypes and optimum planting date. The study was conducted in two locations namely Mgbakwu (06°17E¹N, 07°04E¹E; 83 masl) and Ishiagu (05°58E¹N, 07°34E¹E; 197 masl) across two years and two seasons in each year. A split-plot design was used with three replications. The results indicated that early planting date gave significantly higher yield and yield components than late planting date in both years and locations. IT 98K-131-2 produced mean grain yield of 1220 kg ha-1 in early planting date and 732 kg ha-1 in late season planting in Ishiagu, while in Mgbakwu, it produced 921 and 326 kg ha-1 in early and late planting dates, respectively. IT 97K-556-4 on the other hand produced mean grain yield of 1154 and 424 kg ha-1 in early and late planting dates, respectively in Ishiagu; while in Mgbakwu, the mean grain yield were 1594 and 251 kg ha-1 for early and late planting dates, respectively. IT 98K-131-2 exhibited the highest mean grain yield attributes in all the environments, indicating broad adaptation; while IT 97K-556-4 was the next highest grain yielder with specific adaptation to early season in Mgbakwu. The two cultivars are therefore recommended to farmers for multiplication and general cultivation in south eastern Nigeria. Key words: Cowpea, growth and yield components, planting date.

Nitrogen recovery by cover crops in relation to time of planting and growth termination

Residual fertilizer nitrogen (N) in soil represents a potential environmental contaminant because of the risk of nitrate (NO3) leaching into ground water. Winter annual grass cover crops can conserve residual soil N; however, their ability to recover N greatly varies with management. A two-year field experiment in the North Carolina Coastal Plain on a State fine sandy loam (fine-loamy, mixed, thermic Typic Hapludult) compared dry matter (DM), N accumulation, and soil inorganic N following rye (Secale cereale L.), winter wheat (Triticum aestivum L.), triticale (Triticum secale L.), black oats (Avena strigosa L.), and fallow (native weeds) in relation to planting (October, November, and December) and growth termination (early March, early April, and late April/early May) dates and levels of residual soil N. Cover crop DM and N accumulations decreased with successive planting date delays (November and December) for each growth termination date in the following spring. In 2000, cumulative DM yields of October- and November-planted cover crops were 3.17 Mg ha−1 (1.41 tn ac−1) and 3.74 Mg ha−1 (1.66 tn ac−1), respectively, which were significantly greater than those of December-planted cover crops (1.90 Mg ha−1 [0.84 tn ac−1]) at the second growth termination date (early April). Cover crop N accumulation increased with a delay in growth termination, although the interaction between cover crop species and the planting date varied. October planting of rye and triticale showed greater N accumulation at a March growth termination date, averaging 37.8 kg N ha−1 (33.7 lb N ac−1) for rye and 37.6 kg N ha−1 (33.5 lb N ac−1) for triticale; these values were 7.8% and 14.1% higher than those of black oat and wheat, respectively, at the same planting and growth termination dates. November-planted wheat showed in the highest N accumulation (average, 57.9 kg N ha−1 [51.7 lb N ac−1]) at the late April/early May termination date; this was 3.8% to 7.9% higher than that of other species. In contrast, black oat showed a greater ability to scavenge soil residual N with a late planting and growth termination date combination (average, 58.7 kg N ha−1 [52.4 lb N ac−1]). The cover crop planting date affected soil inorganic N distribution at each termination date, with an October planting date resulting in lower soil profile inorganic N levels than November and December planting dates. Lower soil inorganic N concentrations were strongly associated with increases in cover crop DM and N accumulation for each growth termination date. These results should help growers identify the best niche for a cover crop with respect to recovering residual soil N in their various rotations.

Growth and Yield Responses of Soybean to Planting Density in Late Planting

Soybean is one of the important food crop around the world. Especially in East Asia, it is the main ingredient for traditional food like soy sauce and soy paste. The double cropping system including soybean following onion, Chinese cabbage, and potato is widely adopted in Southern region of Korea. In this system, sowing date of second crop (soybean) can be delayed depending on first crops' growth period and weather condition. When planting date is delayed it is known that soybean yield is declined because of shorter vegetative growth period and earlier flowering induced by warm temperature and changes in photoperiod. The objective of this study was to determine soybean growth and yield responses as plant populations at late planting date. Field experiment was conducted at Department of Functional Crop, National Institute of Crop Science, RDA located in Miryang, Gyeongsangnam-Do for two years ('13-'14) in upland field with mid-late maturity cultivar Daewon. A split-plot block design was used with three replications. Main plots were three sowing dates from June 20 to July 20 with 15 days intervals, and subplots were 4 levels of planting densities. Data of maturity (R8) was recorded, yield components and yield were examined after harvesting. Experimental data were analyzed by using PROC GLM, and DMRT were used for mean comparison. Optimum planting population for maximizing soybean yield in late planting which compared with standard population. In mid-June planting, higher planting density causes increased plant height and decreased diameter which lead to higher risk of lodging, however, reduced growth period due to late planting alleviated this problem. Therefore higher seeding rates can provide protection against low seedling emergence caused by late planting in this region.

Planting Date and Variety Selection for Management of Viruses Transmitted by the Wheat Curl Mite (Acari: Eriophyidae).

Wheat is an important food grain worldwide, and it is the primary dryland crop in the western Great Plains. A complex of three viruses (Wheat streak mosaic, Wheat mosaic, and Triticum mosaic viruses) is a common cause of loss in winter wheat production in the Great Plains. All these viruses are transmitted by the wheat curl mite (Aceria tosichella Keifer). Once these viruses are established, there are no curative actions; therefore, prevention is the key to successful management. A study was designed to evaluate preventative management tactics (planting date, resistant varieties) for reducing the impact from this virus complex. The main plot treatments were three planting dates, and split-plot treatments were three wheat varieties. Varieties were planted at three different times during the fall to simulate early, recommended, and late planting dates. The varieties evaluated in this study were Mace (virus resistant), Millennium (mild tolerance), and Tomahawk (susceptible). Measurements of virus symptomology and yield were used to determine virus impact. Results consistently showed that the resistant Mace yielded more than Millennium or Tomahawk under virus pressure. In some years, delayed planting improved the yields for all varieties, regardless of their background; however, under the most severe virus pressure the combination of both management strategies was not sufficient to provide practical control of this complex. These results illustrate the importance of using a combination of management tactics for this complex, but also reinforce the importance for producers to use additional management strategies (e.g., control preharvest volunteer wheat) to manage this complex.

Effect of late planting and shading on cotton yield and fiber quality formation

Due to the competition of temperature and light resources during the growing season of double cropping system (cotton-rapeseed or cotton-wheat), cotton is generally late-germinating and late-maturing and has to suffer from the two factors of declining temperature and low light especially in the late growth stage. In this study, late planting (LP) and shading were used to fit the two-factor interaction stress, and to investigate their effects on lint yield and fiber quality formation. Two cotton cultivars, Kemian 1 and Sumian 15, were grown in the field in 2010 and 2011 at three planting dates with three shading levels. Among the three yield components, boll weight and boll number were the most sensitive indices to cool temperature and low light, respectively. The two-factor interaction of cool temperature and low light had a significantly effect on boll weight and lint percentage. Fiber length under shading increased throughout the extended duration of fiber elongation (T(Len)) in the normal planting date of 25-April (NPD25-April), and by the decline of maximum fiber elongation rate (V(Len)max) in the late planting dates (LPD). Fiber strength was reduced under the two-factor interaction of NPD25-April and shading due to the decrease of the duration and the mean strengthen rate of fiber strength growth periods. With further temperature decreasing, shading reduced strength mainly due to lower cellulose content and fiber biomass. In addition, compared to Sumian 15, Kemian 1 had higher V(Len)max and longer T(Mic) (data not shown) under the two-factor interaction of LP and shading, leading to longer fiber length and smaller decline of micronaire, and also had a lower decline in strength because of the smaller decline of fiber cellulose content and biomass. Therefore, cotton cultivar of Kemian 1 with a higher V(Len)max, longer T(Mic) and a less decline in cellulose content and biomass were more tolerant to the two-factor interaction.

Influence of late planting on light interception, radiation use efficiency and biomass production of four sweet sorghum cultivars

As a measure of a plants ability to convert solar energy into biomass, radiation use efficiency (RUE) can be used to compare species and genotypes within species. Despite considerable research on RUE of biofuel species, few reports on sweet sorghum (Sorghum bicolor (L.) Moench.) RUE are available. Radiation use efficiency and biomass yield of four sweet sorghum genotypes (‘Dale’, ‘M 81E’, ‘Topper 76-6’, and ‘Sugar Drip’) was assessed in response to two late planting dates in a two-year study. The late planting dates would coincide with abandoning double-crop plantings of soybean following wheat. Aboveground biomass yield and RUE (gbiomassMJ−1 intercepted photosynthetically active radiation (IPAR)) was measured every two weeks beginning four weeks after planting. Two estimates of RUE were calculated differing only in growth periods used (emergence to anthesis [EA] and during rapid linear growth [Max]). Biomass yields, EA, and Max RUE were similar between years and sorghum cultivars, but differed between planting dates. Early-July plantings resulted in greater RUE than mid-July plantings. Averaged across cultivars at the first planting date both years EA and Max RUE were 3.11 and 3.96gMJ−1IPAR, respectively, compared to 2.40 (EA RUE) and 2.79gMJ−1IPAR (Max RUE) at the second planting date. Mean biomass yield across years and cultivars was 10.67 and 8.63Mgha−1 at the first and second planting dates, respectively. These results confirm expected decreases in RUE and biomass production of late-planted sweet sorghum, but also illustrate that, even when planted late, sweet sorghum efficiently converts intercepted PAR to biomass.