Maximizing yields in rice–groundnut cropping sequence through integrated nutrient management

Integrated use of organic and inorganic fertilizers can improve crop productivity and sustain soil health and fertility. The present research was conducted to study the effects of application of green manures [sesbania (Sesbania aculeate Poiret) and crotalaria (Crotalaria juncea L.)] and farmyard manure on productivity of rice (Oryza sativa L.) and its residual effects on subsequent groundnut (Arachis hypogaea L.) crop. Rice and groundnut crops were grown in sequence during rainy and post-rainy seasons with and without green manure in combination with different fertilizer and spacing treatments under irrigated conditions. The results showed that application of green manures sesbania and crotalaria at 10 t ha⁻¹ to rice compared to no green manure application significantly increased grain yield of rice by 1.6 and 1.1 t ha⁻¹, and pod yields of groundnut crop succeeding rice by 0.25 and 0.16 t ha⁻¹, respectively. There was no significant difference between the application of crotalaria or farmyard manure at 10 t ha⁻¹ on grain yields of rice, but pod yields of subsequent groundnut crop were greater with application of green manure. There was no significant effect of different spacing 20×15,15×15,15×10 cm² (333 000; 444 000; 666 000 plant ha⁻¹, respectively) on grain yield of rice. Pod yields of groundnut were significantly greater with closer spacing 15×15 cm² (444 000 plants ha⁻¹) as compared to spacing of 30×10 cm² (333 000 plants ha⁻¹). Maximum grain of rice was obtained by application of 120:26:37 kg NPK ha⁻¹ in combination with green manures, whereas maximum pod yield of groundnut was obtained by residual effect of green manure applied to rice and application of 30:26:33 kg NPK ha⁻¹ in combination with gypsum applied to groundnut crop.     

Foliar sprays of concentrated urea at maturity of pigeonpea to induce defoliation and increase its residual benefit to wheat

The pigeonpea (Cajanus cajan (L.) Millsp.) crop retains appreciable amounts of green foliage even after reaching physiological maturity, which if allowed to defoliate, could augment the residual benefit of pigeonpea to the following wheat (Triticum aestivum L.) in a pigeonpea–wheat rotation. The effect of addition of leaves present on mature pigeonpea crop to the soil was examined on the following wheat during the 1999/2000 growing season at Patancheru (17°4′N, 78°2′E) and during the 2001–2003 growing seasons at Modipuram (29°4′N, 77°8′E). At Patancheru, an extra-short-duration pigeonpea cultivar ICPL 88039 was defoliated manually and using foliar sprays of 10% urea (30 kg/ha) and compared with a millet (Pennisetum glaucum (L.) R.Br.) crop, naturally senesced leaf residue and no-leaf residue controls. At Modipuram, the effect of 10% urea spray treatment on mature ICPL 88039 was compared with the unsprayed control. At both locations, the rainy season crops were followed by a wheat cultivar UP 2338 at four nitrogen levels applied in a split plot design, which at Patancheru were 0, 30, 90 and 120 kg N ha⁻¹ and at Modipuram 0, 60, 120 and 180 kg N ha⁻¹. At Patancheru, urea spray added 0.5 t ha⁻¹ of extra leaf litter to the soil within a week without significantly affecting pigeonpea yield. This treatment, however, increased mean wheat yield by 29% from 2.4 t ha⁻¹ in the no-leaf residue pigeonpea or pearl millet plots to 3.1 t ha⁻¹. At Modipuram, the foliar sprays of urea added more leaf litter to the soil than at Patancheru. Here, increase in subsequent wheat yield due to additional pigeonpea leaf litter was 7–8% and net profit 21% more than in the unsprayed control. The addition of pigeonpea leaf litter to the soil resulted in a saving of 40–60 kg N for the following wheat crops in both the environments. The results demonstrated that pigeonpea leaf litter could play an important role in the fertilizer N economy in wheat. The urea spray at maturity of the standing pigeonpea crop significantly improved this contribution in increasing wheat yield, the effect of which was additional to the amount of urea used for inducing defoliation. The practice, if adopted by farmers, may enhance sustainability of wheat production system in an environmentally friendly way, as it could reduce the amount of fertilizer N application to soil and enhance wheat yield.     

Effect of mulch on soil temperature,moisture, weed infestation and yield of groundnut in northern Vietnam

Groundnut (Arachis hypogaea L.) is one of the chief foreign exchange earning crops for Vietnam. However, owing to lack of appropriate management practices, the production and the area under cultivation of groundnut have remained low. Mulches increase the soil temperature, retard the loss of soil moisture, and check the weed growth, which are the key factors contributing to the production of groundnut. On-farm trials were conducted in northern Vietnam to study the impact of mulch treatments and explore economically feasible and eco-friendly mulching options. The effect of three mulching materials (polythene, rice straw and chemical) on weed infestation, soil temperature, soil moisture and pod yield were studied. Polythene and straw mulch were effective in suppressing the weed infestation. Different mulching materials showed different effects on soil temperature. Polythene mulch increased the soil temperature by about 6 °C at 5 cm depth and by 4 °C at 10 cm depth. Mulches prevent soil water evaporation retaining soil moisture. Groundnut plants in polythene and straw mulched plots were generally tall, vigorous and reached early flowering. Use of straw as mulch provides an attractive and an environment friendly option in Vietnam, as it is one of the largest rice growing countries with the least use of rice straw. Besides, it recycles plant nutrients effectively.     

Effects of varying nitrogen doses on yield,yield components and artemisinin content of Artemisia annua L.

Artemisia annua L. is an aromatic-antibacterial herb that destroys malarial parasites, lowers fevers and checks bleeding, and of which the secondary compound of interest is artemisinin. The objective of the present study was to determine yield, yield components and artemisinin content of A. annua L. grown under four nitrogen applications (0, 40, 80 and 120 kg ha⁻¹) in the Çukurova region of Turkey in 2004 and 2005. Field trials were conducted at Çukurova University, Agricultural Faculty Field Crops Department. In the study, plant height, number of branches, fresh herbage yield, dry herbage yield, fresh leaf yield, dry leaf yield, essential oil content and artemisinin content (by high performance liquid chromatography, HPLC) were examined. By analysis of variance, nitrogen doses had no any statistical effect on the traits investigated except for artemisinin content. Artemisinin content of the dried leaves were significantly affected by nitrogen applications, which varied from 6.32 to 27.50 mg 100 g⁻¹. Contents were from 120 and 80 kg ha⁻¹ nitrogen for the years of 2004 and 2005, respectively.     

Variation in grain quality of pearl millet from Sahelian West Africa

Agricultural intensification through the application of mineral fertilizers, the recycling of crop residues and animal manures and through plant breeding are the only means to increase food supply in the poverty ridden West African Sahel, where pearl millet (Pennisetum glaucum (L.) R. Br.) is the dominant staple. Research on the effects of soil amendments on the quality of millet straw and grain is scarce, comparative studies of possible quality differences in traditional landraces versus improved varieties and hybrids are lacking. This paper reports results from 22 landrace populations, 22 improved varieties, six inbred×variety hybrids (IVHs, fertile inbred×open-pollinated varieties) and four topcross hybrids (TCHs, male-sterile line×open-pollinated varieties), whose grains were analyzed for protein concentration and amino acid composition, macro- and micronutrients (total and phytate P, K, Ca, Mg, Zn, Cu), metabolizable energy (ME), fat and β-carotene. At similar yield levels, landraces showed a 2.9 and 3.5% higher protein concentration compared with improved varieties and hybrids without a detrimental effect on protein quality as determined by the relative amount of lysine and threonine. Landrace populations also had the highest fat concentrations and the largest micronutrient densities. However, in-vitro digestibility and ME were (79.8% and 12.2 MJ kg⁻¹ respectively) larger for both groups of hybrids. The concentration of β-carotene was (0.13 μmol kg⁻¹) highest in the improved varieties, but appeared overall too low to significantly contribute to vitamin A nutrition in local diets. While the results of this genotype screening need to be verified in replicated multi-location trial studies, they underline the potential of including landraces in breeding programs to concurrently improve grain yield and grain quality in this area of the world.     

Radiation interception and the accumulation of biomass and nitrogen by soybean and three tropical annual forage legumes

Field experiments were conducted at Gatton and Dalby in southeastern Queensland to determine parameters associated with radiation interception and biomass and nitrogen (N) accumulation for the ley legume species, phasey bean (Macroptilum lathyroides (L.) Urban) and vigna, (Vigna trilobata (L.) Verdc.). Sesbania (Sesbania cannabina Retz.), a native legume species, and soybean (Glycine max (L.) Merrill)) were included in the study for comparison. The most important differences between species related to differences in radiation interception, radiation-use efficiency (RUE), N-accumulation efficiency and the partitioning of N to plant parts. During early growth, soybean intercepted more radiation than the other species, primarily because of its greater leaf area index (LAI). Sesbania had the highest RUE (1.08 g MJ⁻¹) followed by phasey bean (0.94 g MJ⁻¹), soybean (0.89 g MJ⁻¹) and vigna (0.77 g MJ⁻¹). The efficiency of N-accumulation was greater in soybean (0.028 g N g⁻¹) and phasey bean (0.030 g N g⁻¹) than in vigna (0.022 g N g⁻¹) and sesbania (0.021 g N g⁻¹). In all species, the proportion of N allocated to leaves declined throughout the experimental period, being more rapid in soybean than in sesbania and phasey bean. Despite this decline in total N partitioned to the leaves, both soybean and phasey bean maintained a relatively stable specific leaf nitrogen (SPLN) throughout the experimental periods although sesbania and vigna displayed rapid decreases in SPLN. The large variation between species in RUE and N-accumulation efficiency indicates that the development of ley legume cultivars with a combination of traits for more efficient legume production, water use and soil N-accumulation in the water-limited environments of the grain belt of eastern Australia may be possible. The sensitivity of forage production, water use and soil N-accumulation to variation in RUE and N-accumulation efficiency needs to be quantified using modeling techniques prior to embarking on screening programs to select appropriate germplasm for evaluation studies.     

Zinc deficiency as a practical problem in plant and human nutrition in Turkey: A NATO-science for stability project

Zinc (Zn) deficiency is a critical nutritional problem for plants and humans in Turkey. About 14 Mha of cropped land in Turkey are known to be Zn deficient, particularly cereal growing areas of Anatolia. In 1993, a joint research project was started in Turkey with the financial support of the NATO-Science for Stability Programme to select and characterize cereal genotypes with high yield and/or high Zn accumulation in grain under deficient supply of Zn.Field, greenhouse and growth chamber experiments were carried to study morphological, physiological and genetic factors determining the bases of genotypical differences in Zn efficiency among cereal species and within cultivars of wheat. Among the cereals, rye had particularly high Zn efficiency (high yield under Zn deficiency). There were large genotypical differences among wheat lines. High Zn efficiency was closely associated with enhanced capacity of some lines to take up Zn from soils, but not with increased Zn accumulation per unit dry weight of shoot or grain. Measurement of Zn-containing superoxide dismutase activity in leaves revealed that an efficient utilization of Zn at the tissue or cellular level is an additional major factor involved in Zn efficiency of cereals.Zinc present in grains from Anatolia seems to be not bioavailable. Phytate : Zn molar ratios in grains, a widely accepted predictor of Zn bioavailability, were extremely high and ranged between 95 and 216 for crops grown severely on Zn-deficient soils of Central Anatolia. In the studies concerning determination of Zn nutritional status of school children in Southeastern Anatolia, most children were found to be of shorter stature and had very low levels of Zn (<100 mg kg⁻¹) in hair.     

Residual effect of poultry litter applied to cotton in conservation tillage systems on succeeding rye and corn

The burgeoning poultry industry in the southeastern US is presenting a major environmental problem of safe disposal of poultry litter (PL). In a comprehensive study, we explored ways of PL use in conservation tillage-based cotton (Gossypium hirsutum L.) production systems on a Decatur silt loam soil in north Alabama, from 1996 to 1999. The study reported here-in presents the residual effects of PL applied to cotton in mulch-till (MT) and no-till (NT) conservation tillage systems in 1997 and 1998 cropping seasons on N uptake, growth, and yield of rye (Secale cereale, L.) cover crop and rotational corn (Zea mays L.) in 1999. Rye was grown without additional N, whereas corn was grown at three inorganic N levels (0, 100, and 200 kg N ha⁻¹). Poultry litter was applied to cotton in 1997 and 1998 at 0, 100, and 200 kg N ha⁻¹. Residual N from PL applied to cotton in 1997 and 1998 produced up to 2.0 and 17.3 Mg ha⁻¹, respectively, of rye cover crop and corn biomass (includes 7.1 Mg ha⁻¹ of corn grain yield) without additional fertilizer. Therefore, in addition to supplying crop residues which reduce soil erosion, increase soil organic matter, and conserve soil moisture, the rye cover crop was able to scavenge residual N left by the cotton crop, which would otherwise, be at risk of being leached and pollute groundwater resources. Poultry litter applied to cotton also increased corn grain quality as shown by up to 100% increase in grain N content compared to the 0N treatment. Using PL with a slower rate of N release compared to inorganic fertilizer to meet some of the N requirements of corn, will not only reduce N fertilizer costs for corn, but will also reduce the risk of nitrate N leaching into groundwater. The maximum amount of crop residues added to the cotton based cropping system by residual N from PL and inorganic N was 21.3 Mg ha⁻¹. This will lead to an increase in soil organic carbon and soil structure in the long term and a reduction in soil erosion, thereby further improving soil productivity, while at the same time, protecting the environment from nitrate pollution and soil degradation. Our study demonstrates that cotton under conservation tillage system in combination with rye cover crop and rotational corn cropping could use large quantities of PL thereby avoiding serious potential environmental hazards.     

Variation within a bread wheat cultivar for grain yield,protein content,carbon isotope discrimination and ash content

The study was undertaken to assess the variation within a bread wheat (Triticum aestivum L.) cultivar, primarily for grain yield, and the implications for wheat breeding. During the 1998–1999 growing season, cv. Nestos was established in a non-replicated (NR-0) honeycomb experiment, in the absence of competition (11 547 plants ha⁻¹). Ten high yielding (H) and 10 low yielding (L) plants were selected, the seeds of which were used to form the respective H and L lines. The 20 lines, along with their original cultivar, were evaluated in two locations either in the absence of competition (11 547 plants ha⁻¹) during the 1999–2000 season or under competition (5 000 000 plants ha⁻¹) during the 2000–2001 season. Results showed significant differentiation between lines for grain yield, determined both in the absence of competition at the single-plant level, i.e. yield per plant (YP), and under competition at the crop yield level, i.e. yield per plot (CY). Significant differences between lines were also found for grain protein content (PC), grain carbon isotope discrimination (Δ), and grain ash content (ASH), either in the absence of competition or under competition. A positive relationship was found between YP and CY (r=0.53,P<0.02). Results showed that selection within a bread wheat cultivar, under very low density and on the basis of individual plant grain yield, could be an effective way to either upgrade or maintain the cultivar, whereas the use of Δ or ASH as indirect selection criteria instead of grain yield was not supported by the study.     

Use of glufosinate-ammonium to control cruciferous weed species in glufosinate-resistant winter oilseed rape

Weed control is an important component of integrated cropping systems. However, cruciferous weeds are difficult to control in conventional winter oilseed rape (Brassica napus L.) and new herbicide options are needed. The aim of this study was to determine the potential for use of glufosinate-ammonium (2-amino-4-(hydroxymethyl-phosphinyl)-butanoic acid) as a flexible post-emergence herbicide for control of cruciferous weeds in glufosinate-resistant winter oilseed rape in the Hercynian dry region of Central Germany. The effects of glufosinate-ammonium (900 g active ingredients ha⁻¹) on chlorophyll fluorescence and dry matter in 4-week-old Sisymbrium loeselii L. (tall hedge mustard), S. officinale (L.) Scop. (hedge mustard), S. altissimum L. (tall tumble mustard), and Descurainia sophia (L.) Webb ex Prantl (flixweed) were assessed under controlled conditions in a growth room. A 2-year field trial was used to investigate the effect of glufosinate-ammonium on the dry matter of S. loeselii. Therefore, different application times (two- to four-leaf stage, five- to six-leaf stage, end of vegetative period in autumn, beginning of vegetative period in spring) and herbicide rates (450 and 900 g a.i. ha⁻¹) were tested.Under controlled growth room conditions, plants of all four cruciferous weed species showed a gradual decrease in the quantum yield of photosystem II. The quantum yield was less than 20% of the control plants measured from 0 to 34 h after application. Dry matter production of all four species was reduced to less than 3% that of the untreated control 4 weeks after application. Under field conditions, dry matter production of S. loeselii varied in dependence on the environmental conditions and was 0–88% of the control plants. Under controlled and field conditions, the results indicate that glufosinate-ammonium is effective in post-emergence control of the tested cruciferous weeds in glufosinate-resistant winter oilseed rape. Under field conditions, weather and crop growth influenced herbicide effectiveness.     

Temporal variation in nitrogen concentration of above ground perennial ryegrass applied different nitrogen fertiliser rates

Perennial ryegrass (Lolium perenne L.) was grown for seed in field trials in order to investigate the temporal variation in plant nitrogen (N) concentration during ontogeny. Crops were sown in three successive years and grown with five N fertiliser rates applied in the autumn and in the spring (autumn–spring): 0–0, 0–50, 0–100, 30–120 or 60–140 kg N ha⁻¹. Within each N fertiliser rate, N concentration in the plants increased from the initiation of spring growth and reached a maximum of 4.8% at 450–500 growing degree-days (GDD) after which it decreased to 0.8% at 1150–1200 GDD. This pattern of plant N concentration was consistently low at each N fertiliser rate and between years whereas the variation in plant N concentration within each year was high as a result of the different N fertiliser rates. Nitrogen fertiliser rate up to 150 kg N ha⁻¹ increased the seed yields.During spring growth 89% of the variation in plant N concentration could be explained by a non-linear function of GDD. Maximum variation occurred at 480 GDD, with a 95% confidence interval between 428 GDD and 540 GDD. Plant N concentrations measured at 424 GDD in 1998, 447 GDD in 1997, and 497 GDD in 1996, and the resulting correlation coefficients (r²) between N concentration and seed yield were 0.81, 0.71 and 0.92, respectively.It is concluded that the variation in plant N concentration during ontogeny in perennial ryegrass is related to different N fertiliser rates and that the greatest variation in plant N concentration was in the period from 428 GDD to 540 GDD.     

Cardinal temperatures for germination and early growth of two Lesquerella species

Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for commercial oilseed production. Understanding the minimum temperatures for germination and seedling growth is important for determining potential areas for lesquerella production. The objectives of this study were to determine the cardinal temperatures for germination and seedling growth, and to screen ecotypes for germination and growth characteristics. A temperature gradient table arrangement was used to observe seed germination over a range of temperatures, and time to germination and shoot appearance. Times to 5 mm root length and 5 mm shoot length were also measured to assess cardinal temperatures for seedling survival and growth. Two different species were examined, L. fendleri and a species we refer to as ‘L. pallida aff.’ because it differed from typical L. pallida plants in chromosome number and in oil quality. We concluded that both germination and growth of L. pallida aff. occurred fastest at 22 °C, whereas L. fendleri germinated earlier at 18 °C, but grew faster at 22 °C. L. pallida aff. also had lower germination than L. fendleri over the range studied. Non-dormant seeds of improved lines of L. fendleri had better performance at temperatures above 22 °C than did unimproved accessions. Lines of L. fendleri selected for high oil content and salt tolerance had similar temperature requirements for germination except for improved line WCL-LO3, the current line being used in production. This line had optimal temperatures 6 °C higher for germination and growth than the other improved lines. Accessions of L. fendleri collected from elevations above 2000 m performed better at warmer temperatures, whereas those collected from elevations below 2000 m tended to perform better at cooler temperatures. Dormant seeds of L. fendleri germinated more quickly at low temperatures and had lower base (<3 °C) and optimal (22 °C) temperatures than non-dormant seeds (>7 °C and 28 °C, respectively). We speculate that this partial dormancy trait allows populations of L. fendleri to exploit a wider range of temperature conditions in the wild in order to thrive in extreme environments.     

Effect of nitrogen supply on leaf appearance,leaf growth,leaf nitrogen economy and photosynthetic capacity in maize (Zea mays L.)

Leaf area growth and nitrogen concentration per unit leaf area, N_a (g m⁻² N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain N_a and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84–6.0 g N pot⁻¹) and five rates (0.5–6.0 g pot⁻¹) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P_max, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (N_a or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P_max and N_a. The results confirm the ‘maize strategy’: leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the ‘potato strategy’ can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the ‘maize strategy’ for adaptation to N limitation.     

The influence of rainfed and limited irrigation conditions and early vs. late plantings on kenaf as a potential industrial crop in the southern High Plains,USA

Kenaf (Hibiscus cannabinus L.) is a nonwoody fiber source with many uses. To evaluate the dry matter yield potential of kenaf at two locations in the southern High Plains of the USA and the effects of late planting/late emergence as a possible replacement for hail damaged cotton, four varieties were grown in 2004 and 2005 at New Mexico State University's Agricultural Science Centers at Clovis, under limited irrigation, and Tucumcari, under rainfed conditions. Each study was a randomized complete block design having four replicates. A year × location interaction existed (P < 0.0469) for kenaf yield largely due to precipitation amount and distribution. Either late planting or late emergence due to low soil moisture at planting significantly reduced yields (3.62 vs. 0.63 Mg ha^?1 for mid-May planting and emergence and early July emergence or planting, respectively, P < 0.0001). Consequently, kenaf would not be suitable for recovering input costs when planted after failure of cotton. The very late maturing variety Gregg had consistently lower numeric yields than Dowling, Everglades 41, and Tainung 2 in all comparisons, with the strongest trend within the emergence date comparison (P < 0.0912). Kenaf varieties should be selected for any location that finish blooming approximately three to four weeks prior to the average first autumn freeze to allow for maximum growth.     

Consistent differences among wheat cultivars in osmotic adjustment and their relationship to plant production

Osmotic adjustment (OA) is generally considered an important component of drought resistance. Several reports by J.M. Morgan [Morgan, J.M., 1983. Osmoregulation as a selection criterion for drought tolerance in wheat. Aust. J. Agric. Res. 34, 607–614; 1992. Osmotic components and properties associated with genotypic differences in osmoregulation in wheat. Aust. J. Plant Physiol. 19, 67–76; 1995. Growth and yield of wheat lines with differing osmoregulative capacity at high soil water deficit in seasons of varying evaporative demand. Field Crops Res. 40, 143–152; Morgan, J.M., Condon, A.G., 1986. Water-use, grain yield and osmoregulation in wheat. Aust. J. Plant Physiol. 13, 523–532] from Australia concluded that consistent genetic differences in OA existed among wheat cultivars and that high OA cultivars tended to yield better than low OA cultivars under drought stress. Our study was performed to assess his results with his and other genetic materials.Two of Morgan’s spring wheat lines with high OA (‘H.Osm-134’) and low OA (‘L.Osm-136’) capacity in addition to eight other diverse spring wheat cultivars were tested for OA and plant production when grown in small plots under a rain exclusion shelter at Bet Dagan, Israel in 1996. OA of five of these cultivars (including Morgan’s lines) was also measured in two independent greenhouse tests in 1997 (Israel) and 1998 (Texas).The five cultivars differed significantly and ranked consistently for OA in all tests. No significant cultivar by test interaction for OA was revealed. OA was well correlated across cultivars between tests. The significantly higher OA capacity of H.Osm-134 as compared with L.Osm-136 was repeated in all tests. OA of all ten cultivars was positively correlated with biomass (r = 0.73; p = 0.02) and yield (r = 0.55; p = 0.09) under pre-flowering drought stress in the rain exclusion shelter. H.Osm-134 line performed significantly (p ≤ 0.05) better than L.Osm-136 line for both biomass and yield under drought stress. We therefore support Morgan’s results and conclude that consistent differences in OA exist among wheat cultivars and that these differences can be associated with plant production under pre-flowering drought stress.     

Water balance and rice growth responses to direct seeding,deep tillage,and landscape placement: Findings from a valley terrace in Nepal

For maximizing water retention and attaining high yields, transplanting into puddled soil (TPR) is often considered the optimal method of rice (Orzya sativa L.) establishment. Alternative management techniques like direct seeding (DSR) and deep tillage have been proposed as mechanisms to improve soil physical properties for subsequent dry-season crops, but the risks to rice are uncertain. In this full factorial study on a valley terrace in Nepal, the influence of tillage (shallow—T₁, deep chisel—T₂, deep chisel + moldboard plough—T₃) and establishment practice (TPR, DSR) on the field water balance and rice performance were evaluated in two adjacent landscape settings (terrace edge “upland”, central terrace “lowland”). Although deep tillage had only modest influences on seepage and percolation (SP) rates in both years (Y₁, Y₂), landscape placement and establishment practice had significant implications for the water balance (e.g. Y₂ SP cm day⁻¹: TPR-lowland = 1.6, DSR-lowland = 2.3, TPR-upland = 4.1, DSR-upland = 6.1). During low rainfall periods, however, soil water potential and drought vulnerability were governed solely by landscape placement. Despite water balance differences, there was little evidence that rice rooting behavior was substantially modified by landscape or establishment method. Weed biomass was higher in DSR, but was uncorrelated with water balance and productivity trends. In Y₁, lower SP rates and more days with continuous flooding were positively associated with rice productivity. DSR yields were significantly lower than TPR in both landscape positions, with the lowland outperforming the upland (Y₁ mt ha⁻¹: TPR-lowland = 6.4, DSR-lowland = 5.2, TPR-upland = 5.7, DSR-upland = 4.7). To determine if N dynamics were contributing to productivity differences, fertilizer nitrogen was increased from 120 to 150 kg N ha⁻¹ in Y₂. Results suggest that DSR performance is comparable – and landscape less important – if nitrogen is non-limiting (Y₂ mt ha⁻¹: TPR-lowland = 6.9, DSR-lowland = 6.5, TPR-upland = 7.0, DSR-upland = 6.5); no aspect of the field water balance was associated with yield variability in Y₂. For direct seeding in N-deficient farming systems, landscape criteria may prove useful for minimizing production risks by identifying field areas with lower SP rates.     

Weed control in a pigeon pea–wheat cropping system

Pigeon pea (Cajanus cajan (L.) Millsp.) seedlings compete poorly against the rapid growth of warm-season annual weeds. Weed control is required before this heat and drought-tolerant legume can be reliably grown in the U.S. southern Great Plains as a potential source of livestock hay between annual plantings of winter wheat (Triticum aestivum L.). Currently, no herbicides are labeled for use on pigeon pea grown in the U.S. Three years of replicated field experiments were conducted to determine the effects of applications (1× and 2× rates) of herbicides (pre-emergence, sulfentrazone + chlorimuron and metribuzin; post-emergence, imazapic and sethoxydim) on weed suppression, pigeon pea dry matter, and carry-over effects on a winter wheat crop. The most abundant summer weeds were broadleaf, and all herbicide treatments, except sethoxydim (grass herbicide), reduced weed densities compared to untreated plots without adversely affecting pigeon pea stands. Imazapic treatments provided the most effective weed control. Overall average pigeon pea dry matter ranged from 75 to 256 g m⁻² with sethoxydim and the untreated control ≤ metribuzin ≤ sulfentrazone + chlorimuron ≤ hand weeded control ≤ imazapic. Compared to the hand-weeded control, imazapic treatments greatly reduced wheat dry matter (1×, 65% and 2×, 91%) and grain yield (1×, 59% and 2×, 93%). Imazapic should not be used unless nontransgenic imidazolinone herbicide tolerant wheat cultivars are planted. While the other herbicides decreased negative effects of weeds on pigeon pea dry matter without greatly affecting productivity of a following wheat crop, appropriate labels for each of these herbicides will be required prior to their use by southern Great Plains pigeon pea producers.     

Effect of growth regulators on yield and fiber quality in ramie (Boemheria nivea (L.) Gaud.), China grass

The effects of two mixtures of four plant growth regulators (choline chloride, gibberellin (GA₃), benzyladenine (6-BA) and NaHSO₃) at 20:9:5:800 mg kg⁻¹ (H1) and 20:42:43:2350 mg kg⁻¹ (H3) (active ingredients), respectively, were investigated on yield and fiber quality in ramie (Boehmeria nivea (L.) Gaud.). The mixtures were sprayed over the canopy at two growth stages (10 and 20 days after the previous cut) of field-grown ramie. The treatments increased raw fiber yield by 13–18%, and improved fiber fineness by 57–349 m g⁻¹, increased number of leaves per plant, and also improved all yield components. Treatment H1 resulted in a denser distribution, smaller diameters and greater quantity of fiber cells in stem cross-section. Physiological responses included improving leaf water status, increasing net photosynthetic rate, and decreasing electrolyte exosmosis rate.