Cm Of Irrigation Research Articles

Effect of moisture stress and growth regulating compounds on water use and yield of transplanted rice

A Field research was carried out at the Wetland Farm, Department of Farm Management, Tamil Nadu Agricultural University, Coimbatore during the Rabi and Summer seasons of 2017 and 2018, to examine the effects of moisture stress and growth-regulating compounds on nutrient uptake, water use efficiency, water productivity, and yield of transplanted puddled rice. Three replications of split plot designs were used for field experiment. The treatments includes foliar applications of growth-regulating compounds, such as chlormequat chloride at 200 ppm, mepiquat chloride at 200 ppm brassinolide at 0.1 ppm , Pink Pigmented Facultative Methylotrophs (PPFM 1%) and Control (No spray) at different growth stages, such as panicle initiation stage, flowering stage, and both panicle initiation and flowering stage. The moisture stress free control is implemented by irrigating the field with 5 cm of irrigation each day after the disappearance of previously ponded water. Treatment combination of moisture stress at panicle initiation stage along with 0.1 ppm brassinolide had recorded to increased WUE of 7.09, 6.68 kg ha-mm-1 and water productivity of 0.71 and 0.67 kg m-3, respectively during Rabi and summer season. Treatment combination of moisture stress at both panicle initiation and flowering stages along with PPFM registered lower WUE with 6.19 and 5.78 kg ha-mm-1 and lower water productivity with 0.62 and 0.58 kg m-3, during both the seasons. it could be concluded that, foliar application of 0.1 ppm brassinolide for mitigating the moisture stress at panicle initiation stage alone and one per cent PPFM spray when crop suffered moisture stress at flowering phase were effective in mitigating the moisture stress in attaining the maximum crop yields.

Effect of differential levels of simulated overhead irrigation on residual herbicides applied to wheat straw–covered soil for barnyardgrass control

AbstractCrop residue can intercept and adsorb residual herbicides, leading to reduced efficacy. However, adsorption can sometimes be reversed by rainfall or irrigation. Greenhouse experiments were conducted to evaluate the effect of differential overhead irrigation level on barnyardgrass response to acetochlor, pyroxasulfone, and pendimethalin applied to bare soil or wheat straw–covered soil. Acetochlor applied to wheat straw–covered soil resulted in 25% to 40% reduced control, 30 to 50 more plants 213 cm−2, and greater biomass than bare soil applications, regardless of irrigation amount. Barnyardgrass suppression by pyroxasulfone applications to wheat straw–covered soil improved with increased irrigation; however, weed control levels similar to bare soil applications were not observed after any irrigation amount. Barnyardgrass densities from pyroxasulfone applications to bare soil decreased with irrigation but did not change in applications to wheat straw–covered soil. Aboveground barnyardgrass biomass from pyroxasulfone decreased with greater irrigation amounts in both bare soil and wheat straw–covered soil applications; however, decreased efficacy in wheat straw–covered soil applications was not alleviated with irrigation. Pendimethalin was the only herbicide tested that displayed reduced efficacy when irrigation amounts increased in applications to both bare soil and wheat straw–covered soil. Barnyardgrass control from pendimethalin applied to wheat straw–covered soil was similar to bare soil applications when approximately 0.3 to 1.2 cm of irrigation was applied; however, irrigation amounts greater than 1.2 cm resulted in greater barnyardgrass control in bare soil applications. No differences between wheat straw–covered soil and bare soil applications of pendimethalin were observed for barnyardgrass densities. These data indicate that increased irrigation or rainfall level can increase efficacy of acetochlor and pyroxasulfone. Optimal rainfall or irrigation amounts required for efficacy similar to bare soil applications are herbicide specific, and some herbicides, such as pendimethalin, may be adversely affected by increased rainfall or irrigation.

Simulated irrigation water productivity and related profit effects in U.S. Southern High Plains cotton production

To explore management practices that increase irrigation water productivity (IWP) in U.S. Southern High Plains (SHP) cotton production, the CROPGRO-Cotton crop simulation model was used to evaluate the yield, IWP, and profit effects of irrigation amount and timing. Using 2005–2019 weather input data from 21 SHP weather stations, lint yields were simulated for each of the 315 station-years under unirrigated ‘dryland’ conditions and 18 increasing total irrigation (TIRR) levels. As TIRR was increased to 55.9 cm median lint yields asymptotically approached a maximum. However, irrigation above 35.6 cm increased the incidence of total irrigation plus growing season rainfall exceeding 100% of potential crop ET, leading to decreasing marginal yield effects and decreasing IWP. The highest median IWP (0.321 kg m−3) was found with both 33.0 and 35.6 cm of total irrigation, with 30.5 cm providing slightly lower IWP (0.320 kg m−3). In analyses of irrigated profitability under varying lint price and pumping cost conditions, 30.5 cm (12.0 in) of irrigation increases profits relative to dryland conditions under all but low lint price and high pumping cost conditions. But as TIRR is reduced the probability of these positive profit effects become similar to an evenly weighted coin flip at about 17.8 cm (7.0 in). Simulations that varied the timing of 30.5 cm of irrigation increased median IWP up to 0.434 kg m−3 by limiting irrigation to cotton’s reproductive and maturation periods, with no irrigation during the initial vegetative period. As a result, these simulations show that applying 30.5–35.6 cm (12.0–14.0 in) of irrigation during cotton’s reproductive and maturation phases, with little or no vegetative irrigation, maximizes IWP in SHP cotton production under current climate conditions.

Cotton Emergence and Yield Response to Planter Depth and Downforce Settings in Different Soil Moisture Conditions

US cotton producers are motivated to optimize planter performance to ensure timely and uniform stand establishment early in the season, especially when planting in sub-optimal field conditions. Field studies were conducted in 2017, 2018 and 2019 to evaluate the effect of seeding depth and planter downforce on crop emergence and yield in cotton planted in different soil moisture conditions. Field conditions representative of dry, normal and wet soil moisture conditions were attained by applying 0, 1.27 and 2.54 cm of irrigation within the same field. Two cotton cultivars (representing a small-seeded and a large-seeded cultivar, 9259–10,582 and 11,244–14,330 seeds kg−1, respectively), were planted at seeding depths of 1.3, 2.5 and 3.8 cm with each seeding depth paired with three different planter downforces of 0, 445 and 890 N in each block. Cotton was planted in plots that measured 3.66 m (four-rows) wide by 10.67 m long. Results indicated that crop emergence was affected by the seeding depth across most field conditions and higher crop emergence was observed in the large-seeded cultivar at 1.3 and 3.8 cm seeding depths in dry and wet field conditions, respectively. Lint yield was also higher for the large-seeded cultivar at the 3.8 cm seeding depth across all field conditions in 2017, and in dry field conditions in 2018. Planter downforce effect on crop emergence varied among the cultivars where the large-seeded cultivar exhibited higher crop emergence than the small-seeded cultivar at 445 and 890 N downforce. Planter downforce of 445 N yielded greater than the 0 and 890 N treatment in dry field conditions in 2017. The study results suggest that matching planter depth and downforce settings for prevalent soil moisture conditions at planting along with appropriate cultivar selection can help in achieving optimal emergence and yield in cotton.

Using Analytical Techniques and Cole Crop Field Responses to Quantify 2,4-D plus Glyphosate Removal from the Surface of Plastic Mulch

Planting cole crops and leafy greens in plastic mulch free of summer and winter annual broadleaf weeds is challenging. Because these crops are often grown as a second or third crop on mulch, weeds emerge in previously punched plant holes, tears in plastic, and row middles. Without the ability to use tillage and with limited herbicide options available for weed control, achieving a weed-free planting window is not often feasible. Additional herbicide options are needed, but their interaction with plastic mulch must be understood. Therefore, research has determined the persistence of preplant applications of 2,4-D tank-mixed with glyphosate applied over plastic mulch. Analytical laboratory analyses of plastic samples from field experiments, in conjunction with bioassays using broccoli (Brassica oleracea var. botrytis L.) and collard (Brassica oleracea var. viridis L.), evaluated herbicide dissipation. Analytical studies determined that 0.5 cm of irrigation after herbicide application and 1 day before planting removed 99% of 2,4-D, and 100% of glyphosate from the plastic mulch. Waiting an additional 14 days after application and irrigation further reduced the amount of 2,4-D on the plastic mulch 88% to 95%. For the field bioassay, preplant applications of 2,4-D tank-mixed with glyphosate resulted in 7% or less visual broccoli or collard injury without influencing crop growth, biomass, early season yield, or total yield as long as the mulch was washed with 0.5 cm of irrigation before planting. These studies also demonstrated there were no differences between the 1× and 2× use rates with respect to all response variables measured. Results suggest that 2,4-D and glyphosate can be effectively removed from the surface of plastic mulch with irrigation or rainfall before planting broccoli and collard.

Goosegrass Control and Turfgrass Injury Following Metribuzin and Topramezone Application with Immediate Irrigation

Goosegrass (Eleusine indica L. Gaertn.) is a problematic C4 weedy grass species, occurring in the warmer regions of the world where it is difficult to selectively control without injuring the turfgrass. Furthermore, control efficacy is affected by plant maturity. End-user options for satisfactory goosegrass control has decreased; thus, the need for developing management techniques to improve the selectivity of POST goosegrass control options in turfgrass systems is ever increasing. One possible means of providing control, yet maintaining turf quality is immediately incorporating applied products via irrigation. Greenhouse and field trials were conducted in Pickens County, SC, with the objectives of 1) evaluating turfgrass injury following use of POST goosegrass control options; 2) assessing if irrigating (0.6 cm) immediately following the herbicide application reduces injury of ‘Tifway 419’ bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy]; and 3) determining if immediate irrigation influences goosegrass control at one- to three-tiller and mature growth stage. Following the application of herbicide treatments, irrigation was applied (+) or not applied (−). Treatments included the following: control (+/− irrigation); topramezone at 12.3 g a.i./ha (+/− irrigation); metribuzin at 420 g a.i./ha (+/− irrigation); and topramezone plus metribuzin (+/− irrigation) at 12.3 and 420 g a.i./ha. Irrigation treatment had minimum effect on greenhouse-grown goosegrass biomass, all treatments provided >85% control of 1- to 3-tiller goosegrass plants. However, control for mature plants was <50% for topramezone- and 60% to 70% for metribuzin-containing treatments. In field studies, at 1 week after treatment (WAT), the irrigated metribuzin and topramezone plus metribuzin had ≈37% and ≈16%, respectively, less goosegrass control vs. nonirrigated treatments. At 2WAT, irrigated metribuzin and irrigated topramezone plus metribuzin–treated plots, had ≈50% less mature goosegrass control vs. nonirrigated treatments. Irrigated herbicide treatments, however, experienced ≈23% less turfgrass injury at this time. At 4 WAT, irrigated metribuzin- and irrigated topramezone plus metribuzin–treated plots experienced reduced mature goosegrass control by ≈65% and ≈59%, respectively. Overall, incorporating POST herbicide applications via 0.6 cm of irrigation reduced turfgrass injury by at least 20% for all herbicide treatments, while maintaining goosegrass control.

Effect of post-application irrigation on fungicide movement and efficacy against Magnaporthiopsis poae

Management of many crown and root diseases of turfgrasses includes the use of fungicides. The physicochemical properties of the fungicides used vary greatly, but most have low mobility and are not phloem mobile, which results in little active ingredient present in the basal and underground structures of turfgrass plants. Two studies were conducted in a laboratory setting to determine the effects of post-application irrigation amounts (0, 0.3, 0.6, 1.3, and 2.5 cm) on the distribution of 14C myclobutanil and 14C tebuconazole in a soil profile of 90% sand and 10% peat moss by volume. In addition, growth chamber experiments were conducted to examine the effect of post-application irrigation amount on azoxystrobin efficacy against summer patch (Magnaporthiopsis poae) in ‘Penn A-4’ creeping bentgrass (Agrostis stolonifera L.). The creeping bentgrass was treated with azoxystrobin and immediately irrigated with 0, 0.25, 0.3, or 0.6 cm of irrigation. Lastly, an in vitro fungicide sensitivity assay was conducted on three M. poae isolates to determine their sensitivities to two succinate dehydrogenase inhibitors (SDHIs), three demethylation inhibitors (DMIs), and four strobilurins (QoIs) to determine if fungicide concentrations in the soil profile reached levels high enough to suppress fungal growth. In both 14C experiments, more than 54% of the 14C was retained in the top 5 cm of soil for all irrigation treatments. For the 14C myclobutanil experiment, lysimeters treated with 2.5 cm of post-application irrigation resulted in 3.9% of 14C recovered in the 7.6–10.2 cm sampling depth, which was higher than all other irrigation treatments. Post-application irrigation at 2.5 cm in the 14C tebuconazole experiment yielded 6.3% of the 14C at the 7.6–10.2 cm sampling depth and 2.3% at the 10.2–12.7 cm sampling depth—recoveries at both depths were higher with 2.5 cm of irrigation than all other irrigation treatments. No 14C was detected below 12.7 cm for either experiment. Less disease was observed when azoxystrobin received post-application irrigation. Both 0.25 and 0.3 cm of post-application irrigation increased turf quality compared to no irrigation; moreover, 0.25 and 0.6 cm of post-application irrigation increased root length compared to no irrigation. In the in vitro fungicide sensitivity assay, isolates of M. poae were sensitive to all fungicides with only minor sensitivity to the SDHIs. In general, isolates were most sensitive to the QoIs with some variability in isolate sensitivities noted. Isolates of M. poae are sensitive to commonly used fungicides and efficacy is enhanced by post-application irrigation due to improved fungicide distribution into the soil profile.

Effect of irrigation levels and frequencies on growth, yield and economics of capsicum production under naturally ventilated polyhouse

The present investigation was carried out with the objective to standardize irrigation scheduling for improving capsicum yield for higher benefit: cost ratio under naturally ventilated polyhouse. The experiment was laid down in Randomized Complete Block Design (RCBD) along with seven treatments comprising of three irrigation depths, two intervals and a farmers practice. The data were recorded on days to first flowering, plant height (cm), days to marketable picking, total harvest duration (days), number of fruits per plant and yield (kg/m2). A perusal of the pooled data (2011 and 2012) revealed that different levels and frequencies of irrigationproduced significant differences with regards to different traits under study. The treatment with 0.25 cm irrigation at alternate day (T2) and farmer’s practice resulted in earliest flowering (41.71 days) and days to marketable picking (72.49 days), respectively. However, application of 0.50 cm of irrigation at alternate day (T4) resulted in maximum plant height (142.65 cm), total harvest duration (131.68 days), number of fruits per plant (18.26) and highest yield (12.76 kg/m2) along with maximum benefit: cost ratio (6.53:1). Hence,treatment T4 may be recommended for commercial cultivation of capsicum in the hilly regions of the country under naturally ventilated polyhouse.

Effect of Irrigation Levels and Frequencies on Yield, Quality and Water Use Efficiency of Capsicum Grown under Protected Conditions

The present investigation was carried out at Experimental Research Farm of the Department of Vegetable Science, Dr. Y.S. Parmar University of Horticulture and Forestry, Nauni, Solan (HP), India during spring-summer seasons of year 2010 and 2011 to standardize the irrigation scheduling for improving capsicum yield, quality and water use efficiency under protected conditions. The experiment was laid down in RCBD with seven treatments having three irrigation depths, two intervals and a farmers practice. The data were recorded on fruit length (cm), fruit breadth (cm), average fruit weight (g), number of fruits plant−1, total biomass production (g/plant), yield plot−1 (kg), total soluble solids (°B), ascorbic acid (mg 100 g−1), root rot incidence (%), water productivity (kg m−2 cm−1) and soil moisture (%). The perusal of the pooled data revealed that different levels and frequencies of irrigation produced significant differences with regards to different traits under study. The treatment with 0.50 cm of irrigation at alternate day resulted in maximum fruit breadth (6.53 cm), average fruit weight (95.20 g), number of fruits plant−1 (18.26), total biomass production (165.38 g plant−1) and highest economic yield plot (36.17 kg plot−1) and along with moderate water productivity (0.25 kg m−2 cm−1), may be recommended for commercial cultivation of capsicum in the hilly regions under naturally ventilated polyhouses. However, the treatment with 0.25 cm of irrigation at alternate day recorded maximum water productivity (0.43 kg m−2 cm−1) and total soluble solids (5.30%) with moderate yield (30.58 kg plot−1) and lowest root rot incidence (2.76%), may be suggested for the high water scare areas for the successful cultivation of capsicum under protected conditions.

Growth of spring canola (Brassica napus) under deficit irrigation in Western Nebraska

Drought is a periodic occurrence in the High Plains of the U.S.A.; thereby low-water using crops are desired. Canola, a biofuel and food oil, has been studied in the region under rain-fed conditions for several years. The study's objective was to measure plant growth, seed yield, and oil characteristic of canola at four levels of applied water in western Nebraska. The cultivar Hyola 357 Magnum was exposed to rain-fed only (RF), and irrigated with 10 (LI), 20 (MI), and 30 (HI) cm water. Adding irrigation increased plant growth, i.e., canopy height, stem length, and canopy weight. Highest canopy height (>100cm for MI and HI) was reached by 10 weeks after planting (WAP) with a total of 23cm of applied water or 13cm of irrigation. By 8 WAP, canopy fresh weight was increased by 37 to 58% by MI and HI irrigations. Pod fresh and dry weights at harvest (13 WAP) were increased >50% and >20%, respectively, by all irrigations. Seed yield were increased by each incremental increase in irrigation from 1220kg/ha for RF to 2905 for HI, a 2.4-fold increase. Seed oil content was increased by MI and HI irrigations (4–8%). The fatty acid profile was not substantially altered by irrigation. There was a slight decrease of palmitic acid and increase in linolenic acid with HI. Canola showed that >20cm of applied water is needed for good vine and pod growth but >40cm was needed to achieve the highest yield. Canola could be grown successfully in western Nebraska, supplying oil for fuel and cooking.

Growth of spring camelina (Camelina sativa) under deficit irrigation in Western Nebraska

The High Plains of the U.S.A. is subject to periodic drought where low-water using crops are desired. Camelina is a potential biofuel crop that may be suitable for this region. The objective was to determine the growth, seed yield, and oil characteristic of camelina exposed to four levels of applied water in western Nebraska. The cultivar Cheyenne was exposed to rain-fed only (RF), and irrigated with 10 (LI), 20 (MI), and 30 (HI) cm water. Irrigation increased plant growth as measured by canopy height, stem length, and canopy weight. Maximum height (70–80cm) was reached by 10 weeks after planting (WAP) with a total of 23cm of applied water or 13cm of irrigation. By 13 WAP, canopy and pod fresh weights were increased by 40–50% by the MI and HI irrigations. Likewise, at harvest (13 WAP), plant dry weight was increased by 50% by the two higher irrigation levels. Seed yields were increased by each incremental increase in irrigation from 890kg/ha for RF to 2540 for HI, a 2.85-fold increase. Oil content was not affected by irrigating at the LI or MI but was increased only by the HI irrigation level. The fatty acid profile was altered by irrigation with an increase in the major constituent, linolenic acid, and a corresponding decrease in two other large constituents, oleic and linoleic acids. There also was a slight increase in the minor constituent of erucic acid. The growth pattern of camelina showed that 23cm of applied water would be required for healthy plant growth but as much as 43cm would be needed for maximum yield. The results indicate that camelina could be grown successfully in western Nebraska, supplying oil for fuel and cooking.

Rate and Application Timing Effects on Tolerance of Covington Sweetpotato to S-Metolachlor

Field studies were conducted in 2011 and 2012 at the Horticultural Crops Research Station near Clinton, NC, to determine ‘Covington' sweetpotato tolerance to S-metolachlor rate and application timing. Treatments were a factorial arrangement of four S-metolachlor rates (0, 1.1, 2.2, or 3.4 kg ai ha−1) and six application timings (0, 2, 5, 7, 9, or 14 d after transplanting [DAP]). Immediately following application, 1.9 cm of irrigation was applied to individual plots. Sweetpotato injury was minimal for all treatments (≤ 10%). No. 1 grade sweetpotato yield displayed a negative linear response to S-metolachlor rate, and decreased from 25,110 to 20,100 kg ha−1 as S-metolachlor rate increased from 0 to 3.4 kg ha−1. Conversely, no. 1 sweetpotato yield displayed a positive linear response to S-metolachlor application timing and increased from 19,670 to 27,090 kg ha−1 as timing progressed from 0 to 14 DAP. Total marketable sweetpotato yield displayed a quadratic response to both S-metolachlor application rate and timing. Total marketable yield decreased from 44,950 to 30,690 kg ha−1 as S-metolachlor rate increased from 0 to 3.4 kg ha−1. Total marketable yield increased from 37,800 to 45,780 kg ha−1 as application timing was delayed from 0 to 14 DAP. At 1.1 kg ha−1S-metolachlor, sweetpotato storage root length to width ratio displayed a quadratic relationship to application timing and increased from 1.87 to 2.23 for applications made 0 to 14 DAP. At 2.2 kg ha−1 of S-metolachlor, sweetpotato length to width ratio displayed a quadratic response to application timing, increased from 1.57 to 2.09 for 0 to 10 DAP, and decreased slightly from 2.09 to 2.03 for 10 to 14 DAP. Application timing did not influence length to width ratio of sweetpotato storage roots for those plots treated with S-metolachlor at either 0 or 3.4 kg ha−1.

Downward Mobility of 14C‐Labeled Simazine in a Bermudagrass System vs. a Fallow Soil System

Pesticides applied to bermudagrass (Cynodon dactylon L.) can be captured by the canopy, absorbed by the roots, or bound in the thatch layer, which reduces the amount available to leach compared with a fallow soil system where pesticides may be applied directly to soil. 14C‐Simazine was applied to dormant bermudagrass and fallow soil in lysimeters in a cold growth chamber (5°C) (cold‐fallow soil) and to actively growing bermudagrass and fallow soil in lysimeters in a greenhouse (25°C) (warm‐fallow soil) in April. Following clipping collection, lysimeters were irrigated with 5 cm of water every 3–4 d, and leachate was collected. After 25 d, lysimeters were divided into 2‐cm increments from 0 to 10 cm, then 5‐cm increments from 10 to 30 cm. Because of evapotranspiration, actively growing bermudagrass and warm‐fallow soil yielded significantly less leachate than dormant bermudagrass and cold‐fallow soil indicating less moisture is available for downward movement during summer. After the addition of 31 cm of irrigation, the greatest quantities of 14C‐simazine were in the 0‐ to 2‐cm increment for all treatments and decreased with depth. Although the greatest quantities of 14C‐simazine in leachate occurred in dormant bermudagrass, the reached factor was greatest for cold‐fallow soil (0.20), followed by dormant bermudagrass (0.17), warm‐fallow soil (0.16), and actively growing bermudagrass (0.14). Therefore, simazine is least mobile in bermudagrass during summer and most mobile in fallow soil in winter.

Chemical, biochemical, and biological impact of untreated domestic sewage water use on Vertisol and its consequences on wheat (Triticum aestivum) productivity

In the peri-urban areas of central India, sewage water is a valuable resource for agricultural production. In this study, impact of domestic sewage water irrigation for 5 years on Vertisol with no previous history of sewage irrigation was investigated in an ongoing field experiment at Bhopal (India) under subtropical monsoon type climate. The wheat (Triticum aestivum) crop was grown during post-rainy winter season with 30 cm of irrigation (groundwater or sewage water) and four nutrient treatments (T(1), 0; T(2), 100%; T(3), 50%; and T(4), 50% of general recommended doses of NPK + FYM at 10 Mg/ha). Results showed that sewage irrigation of about 150 cm over a period of 5 years resulted significant increases in salinity as well as available fractions of N, P, K, and micronutrients, viz., Zn, Fe, and Mn in soils. Carbon and phosphorus applied through sewage water were accumulated more in subsoil layer compared to topmost plough layer. Soil microbiological activity, as indicated by soil respiration, microbial biomass C, as well as dehydrogenase enzyme activity was higher in sewage water-irrigated soils. There was also significant increase in fungal and actinomycetes as well as total coliform population in such soils. Nutrients supplied through sewage water were not able to raise the productivity of wheat to the level that obtained through fertilizers at the recommended level which indicated that additional nutrients through fertilizers are required to obtain higher productivity of wheat under sewage farming. Protein and Zn content in wheat grains were more when the crop was grown with sewage irrigation. Overall results show that except for increase in coliform population, short duration (5 years) of municipal sewage water irrigation did not have any appreciable harmful effect on soil quality as well as crop productivity; rather, it proved beneficial in improving soil fertility, wheat productivity, and produce quality.

Water Stress and Growth of Native and Introduced Shrub Species as Influenced by Irrigation Regime

Native plants are often promoted as an approach for water conservation in urban landscapes. However, information regarding plant water needs is based primarily upon anecdotal observations of plant performance. Direct comparisons between native and introduced species using physiological measures of plant water stress are unavailable to support or refute such recommendations. Ligustrum japonicum and Myrica cerifera, representing an introduced and native species, respectively, were transplanted into a fine sand soil to evaluate establishment rates and growth characteristics under two irrigation regimes. Each species was irrigated either daily or every 3 days and received 1.3 cm of irrigation per event for 8 months after transplant. Predawn, midday, and dusk water potentials were recorded on three consecutive days monthly, with cumulative stress intervals calculated. Height, growth indices, shoot dry mass, root dry mass and leaf area were also recorded. Water potential was significantly influenced by day of water stress level. On days without irrigation, water stress was generally greater and affected growth. Myrica irrigated daily had the greatest growth, yet plants receiving irrigation every 3 days had the least growth and greater leaf drop. In contrast, for Ligustrum there were no differences between irrigation regimes in growth responses except for growth index.

Supplemental Irrigation at Reproductive Growth Stages to Improve Popcorn Grown at Different Populations

When irrigation sources are limited, supplemental irrigation at selected growth stages may help avoid crop stress. The objective of this study was to determine the effect of limited, supplemental irrigation at two reproductive growth stages of popcorn (Zea mays L.) grown at different populations. The experiment was conducted from 1995 through 1998 on a Parsons silt loam (fine, mixed, thermic Mollic Albaqualf). The experimental design was a randomized complete block with a split‐plot arrangement of treatments. Six irrigation schemes of no irrigation, application of 2.5 or 5 cm at R1 (silk stage) or R3 (milk stage), and 2.5 cm at both R1 and R3 were main plots, and populations of 37000, 49000, and 62000 plants ha−1 were subplots. Popcorn yield was affected by irrigation in only 2 of 4 yr. In the driest growing season (1996), yields were low, but either 2.5 or 5 cm of irrigation applied at R1 increased yields by 60% or more compared with irrigations at R3 or no irrigation. In 1997, 2.5 cm of irrigation at R1 or 2.5 cm at both R1 and R3 resulted in 23 to 27% greater yield than with no irrigation. These responses were partially explained by 12 to 13% greater number of kernels per ear. The optimum plant population was 49000 plants ha−1; this treatment maximized yield, kernel weight, and produced one ear per plant. Responses to irrigation were not affected by plant populations for any measured parameters. Popping expansion ratio was unaffected by treatments. Supplemental irrigation at critical reproductive growth stages influences yield but is inadequate to provide consistent yield and quality improvements for popcorn grown in the eastern Great Plains.

Normal and Flush Irrigation Effects On Phosphorus Leaching from Simulated Golf Greens in the Greenhouse

Fertilizer nutrients have the potential to leach from porous golf greens, especially when “flushing” is practiced where 8 or 10 cm of irrigation is applied. A greenhouse experiment was carried out with 52 cm columns (15 cm diameter) made to United States Golf Association green specifications and sodded to ‘Tifdwarf’ bermudagrass to determine the amounts of phosphorus leached for two fertilizer sources (20–20–20 and superphosphate) at three rates (0, 5, and 11 kg ha−1 added every other week for a total of 6 weeks) and two irrigation schemes (normal irrigation at 6.3 mm day−1 and the same irrigation with an additional four flushes of 8 cm each). Weekly leachate collections for 29 weeks were analyzed for soluble P. Flushes resulted in higher P concentrations in the leachate where as much as 40% of the added P was recovered in the leachate. In contrast, normal irrigations resulted in less than 10% of the P applied moving through the columns. The two fertilizer sources gave essentially similar results. The higher P rate caused higher concentrations of P in the leachate, but P concentrations for the low rate for normal irrigation were not different than the control. For flushes, the extractable P in the top 15 cm of the rooting media was lower than for normal irrigation and the extractable P in the columns was higher. Results indicate that low rates of P should be applied to golf greens and, if flushing is practiced, it should be done when little P is in the rooting media.

Effects of Slope and Underlay on Surface Runoff of Irrigation from Woven Polypropylene Groundcloth

Woven polypropylene groundcloth is used extensively in plant nurseries as a permeable and durable surface for container plant production. To better understand the fate of overhead sprinkler irrigation water, we designed and constructed runoff platforms (2.7 m2) to measure runoff and leachate from single irrigation events as affected by slope and underlay substrates. Groundcloth-covered platforms at slopes of 1.5% and 11% were tested with each of five underlay treatments: no underlay, coarse sand, 50% coarse sand and 50% no underlay (CS50), gravel, and native sandy soil. We applied 0.9 cm of irrigation at 1.8 cm·h-1 and determined runoff and leachate volumes. Runoff percentage [runoff × 100%/(runoff + leachate)] increased at the 11% slope for each underlay treatment. Mean (n = 10) runoff percentages (RP) for the 1.5% and 11% slopes were 0.5% and 15.7%, respectively, for no underlay, 0.1% and 1.1% for coarse sand, 0.1% and 0.7% for CS50, 0.7% and 2.5% for gravel, and 0.1% and 3.1% for native sandy soil. The low RP observed indicate that a high percentage of nutrients and agrichemicals associated with container leachate would move into the underlying substrate or soil rather than directly running off into surface waters.

Formulation effects on isoxaben and trifluralin in runoff water from container plant nurseries

Abstract Sprayable and granular formulations of isoxaben and trifluralin were applied to container plant nursery beds to determine formulation effects on herbicide runoff and weed control. In 1998 herbicide application was followed by 0.8 cm of irrigation delivered in 60 min, and runoff water samples were collected on the day of application (DOA). The highest concentrations of isoxaben and trifluralin detected in runoff water were 0.50 and 0.15 μg ml−1, respectively. Total isoxaben in runoff water was greater from the granular than from the sprayable formulation, but no differences attributable to formulation were detected for trifluralin. In 1999 herbicide application was followed by irrigation applied in three pulse cycles of 30 min each (0.8 cm per cycle). Runoff water samples were collected daily through 2 d after herbicide application (DAA). The highest herbicide concentrations were found in the first runoff sample on the DOA. Isoxaben was detected at 1.6 μg ml−1 from both formulations, and triflural...

Horizontal and vertical movement of Pseudomonas fluorescens toward exudate of Macrophomina phaseolina in soil: influence of motility and soil properties

The role of motility and cell surface hydrophobicity in transport and dispersal of Pseudomonas fluorescens strains LAM1-hydrophilic, LAM2-hydrophobic and LAM(NM) (non-motile mutant of LAM2) under different soil conditions was studied. Maximum adhesion was recorded for LAM2 in clay loam (70%), followed by sandy loam (68%) and sandy soil (40%). Vertical migration of P fluorescens isolates in soils was recorded at 5 and 25 cm flow of wafer or M. phaseolina exudate. In all the treatments, LAM1 exhibited maximum migration followed, by LAM2 and LAM(NM). The rate of migration of such isolates was lowered in water irrigated soils compared to those irrigated with M. phaseolina exudate. In sandy soil, cells of LAM1 migrated up to 13 cm in comparison to LAM2 (11 cm) and LAN(NM) (9 cm) at 5 cm flow of fungal exudate. Population of LAM1, LAM2 and LAM(NM) was 5.7, 5.68 and 5.61 log cfu g(-1) soil at 1 cm depth, but it decreased to 2.56, 2.21 and 1.99 log cfu during migration up to 11 cm in sandy soil at 5 cm flow of fungal exudate. Greater motility was observed in sandy soil irrigated with water or fungal exudate, followed by sandy loam and clay loam. In general, filtration coefficient (lambda) of P. fluorescens was higher in soils irrigated with 5 cm of water or exudate than with 25 cm of irrigation. The horizontal movement of P. fluorescens strains in sandy soil adjusted at different psi m showed marked reduction with decrease in psi m. The non-motile LAN(NM) did not show chemotactic response and migrated up to a maximum of 3 mm in saturated soils (0 kPa). After 96 h, LAM1 and LAM2 migrated upto 35 and 29 mm respectively in sandy soil. Motile isolates had significantly greater colonization of M. phaseolina sclerotia over the non-motile mutant.