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Increasing soil salinity due to climate change complicating weed management. Rhynchosia capitata is becoming an increasing problem in summer crops, such as cotton, soybean, pearl millet and mungbean worldwide. Study was conducted to evaluate the impact of four types of salts stresses (NaCl, Na2SO4, CaCl2 and NaHCO3) at six different levels (0, 50, 100, 150, 200 and 250 mM) on R. capitata seeds of different sizes including small, medium and large. Results revealed that R. capitata can germinate over a wide range of salt stress but as the salinity level was increased to 250 mM the germination percentage and seedling growth decreased significantly. Larger seeds have more potential to germinate and grow vigorously at an increased salt concentration as compared to medium and small seeds. Salt stress caused 40-73%, 59-96% and 40-100% inhibition in seed germination, seedling length and dry weight, respectively. Among various salt stresses CaCl2 showed less inhibition of R. capitata. The higher tolerance of this weed to wide range of salt stresses is alarming factor under current and anticipated increase in salinity, as it will disturb management plans by changing critical completion period and threshold level due to more adaptability of weed under stress than crop plants.

Drought is one of the commonly occurring environmental stresses, limiting crop production in many countries. Selection of cultivar is the most effective and economical means for alleviating the adverse effects of drought stress on crops. The present study aimed to investigate the growth, some physiological processes, yield and quality of some newly-developed wheat cultivars (AARI-2011, AAS-2011, Faisalabad-2008, Millat-2011 and Punjab-2011) under field drought stress conditions. The cultivars were sown in a field under normal irrigation and drought-induced conditions. Maximum net photosynthetic rate was recorded in cv. AAS-2011 at growth stage of 67 days after wheat emergence under normal irrigation and cv. Faisalabad-2008 at 67 days after wheat emergence under drought condition. Leaf stomatal conductance and transpiration rate were maximum in cv. Faisalabad-2008 under drought conditions. The adverse effects of drought stress were observed more on cv. Millat-2011 than Faisalabad-2008, with respect to net photosynthetic rate and transpiration. Drought exerted a significant adverse effect on leaf stomatal conductance at 74 days after wheat emergence which was recorded as 230 mmol m-2 s-1. Among the cultivars, AAS-2011 recorded maximum yield traits and grain yield under normal irrigation condition and Faisalabad-2008 under drought condition. Cultivar Millat-2011 was the most susceptible to drought and Faisalabad-2008 the most resistant to drought. Faisalabad-2008 maintained the quality at the most under drought stress conditions. It is concluded that Fasialabad-2008 should be grown under field drought conditions to achieve maximal yield and quality of wheat.

Widespread resistance in Phalaris minor is a major challenge for sustainable wheat production. Recently, multiple resistance and cross resistance in this weed increased the concerns of wheat growers. The use of potential integrated resistance management strategies including allelopathic crop mulches and herbicide mixtures is crucial in assuring sustainable production. A two-year field trial was conducted during 2014–15 and 2015–16 in wheat to evaluate the efficacy of allelopathic mulches of sunflower, rice, maize, and sorghum alone and in combination with three types of herbicide mixtures. Post-emergence herbicide mixtures used in this study were clodinafop –propargyl plus metribuzin, sulfosulfuron plus clodinafop-propargyl, and pinoxaden plus sulfosulfuron at 50% of recommended doses. Integrated use of allelopathic crop mulches and herbicide mixtures provided effective control of P. minor in wheat. However, application of allelopathic mulches and herbicide mixtures alone did not provide a satisfactory control of P. minor. In addition, the application of allelopathic mulches caused a significant decay (23–52%) of soil weed seed bank. The integrated use of mulches and herbicide mixtures consistently enhanced the wheat yield by 23–39% and 24–35% during 2014–15 and 2015–16, respectively. These findings, as the first indication of the potential integration of allelopathic mulches and post-emergence herbicide mixtures to manage P. minor in wheat fields, would help control resistant P. minor and delay further herbicide resistance in this weed.

Sustainable crop production under changing climate is crucial to feed the increasing population of the world. Efforts are underway to discover novel strategies to ensure global food security. Allelopathy is one such phenomenon that can help in this regard. It is a direct or indirect and positive or negative effect of plant species on other plant species and microorganisms, through the release of secondary metabolites known as allelochemicals. Brassica species are well known for their allelopathic potential as most of them endogenously produce potent allelochemicals such as glucosinolates, allyl isothiocyanates, and brassinosteroids. These allelochemicals are highly phytotoxic to target species when released at high concentrations and, therefore, affect their growth and development. This review illustrates the potential role of Brassica allelopathy for crop production in modern agriculture. Allelopathic potential of Brassica species can be utilized for weed management by using them as cover crops, companion crops, and intercrops, for mulching and residue incorporation, or simply by including them in crop rotations. Similarly, the expression of allelochemicals from these species have great value in the management of crop pests and diseases, and abiotic stresses. Most of these allelochemicals can also act as crop growth promoters when released or applied at low concentrations. Although the use of chemical herbicides, pesticides, and synthetic growth regulators is currently inevitable for crop production, the use of ecological options like allelopathy may help in achieving global food security sustainably. Exploring the potential of Brassica allelopathy could be promising in achieving higher productivity without compromising the environmental safety.

Alligator weed (Alternanthera philoxeroides) is the most troublesome invasive weed in transplanted rice ecosystems worldwide. A two-year field study was conducted to estimate economic threshold lev...

A great deal of work has been done to explore the hormetic potential of various herbicides to enhance crop growth and yield. However, the growth stimulatory potential of plant-released phytotoxins at low rates to enhance crop yield has not yet been realized, as most of the research has focused on the herbicidal potential of these phytotoxins. However, hormesis of plant-released phytotoxins is a more practical aspect, as these are present at low concentrations in field conditions. These phytotoxins are biodegradable and safe for the environment, and have the potential for crop enhancement both under controlled and field conditions. Low doses of plant-released phytotoxins have been reported to enhance crop growth by up to 50% under controlled conditions, and crop yield by up to 42% under field conditions. In this review, we have discussed hormesis of plant-released phytotoxins with examples. In addition, we discuss the potential for crop enhancement, the influence of different factors on the expression of hormesis, as well as the potential for both undesirable (in weeds) and desirable hormesis (in crop plants). The use of plant-released phytotoxins as growth regulators is also discussed, focusing on sustainable crop production. In future, phytotoxins may be utilized as a crop stimulator to enhance crop yield, especially in organic crop production systems.

A field survey was conducted for the sampling of Acetyl-CoA carboxylase (ACCase) inhibitor resistance littleseed canarygrass, a major weed of wheat, from Punjab, Pakistan in 2014 for confirmation of resistance. The surveyed regions encompassed four different cropping systems including rice–wheat, maize–wheat, cotton–wheat and mixed cropping. Dose–response assay was conducted for confirmation of resistance. Efficacy of herbicide mixtures including clodinafop–propargyl, metribuzin, pinoxaden and sulfosulfuron at a range of doses was investigated to manage littleseed canarygrass. Results revealed that all populations were resistant to fenoxaprop except PM-BWL-2. The higher level resistance (6.5) was found in populations collected from rice–wheat cropping system. The tested herbicide mixtures at 75% and 100% of the recommended dose of each mixture component provided the effective control of resistant littleseed canarygrass. Mixtures at 50% provided more than 80% control and reduced growth and seed production potential of surviving plants. The confirmation of ACCase inhibitor resistance as the first case of herbicide resistance in Pakistan, leads us to discourage use of ACCase inhibitor herbicides alone. However, herbicide mixtures at 75% and 100% of the recommended dose are suggested to manage this weed for sustainable wheat production in the surveyed cropping systems.

Little is known of glyphosate-induced hormesis in weeds and how this might influence weed management. To test the hormetic effect of low doses of glyphosate on broad-leaved weeds, two experiments were conducted, in the laboratory and the screenhouse. The hormetic effects of glyphosate solution in growth media (0, 65, 130, 250, and 500 g acid equivalent (a.e) ha−1) and foliar spray (0, 4, 8, 16, 32, and 64 g a.e. ha−1) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus, and Lathyrus aphaca). Glyphosate solution in the range 65–250 g a.e. ha−1 stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha−1 inhibition of germination and growth was observed. Foliarly applied glyphosate in the range 4–32 g a.e. ha−1 increased root and shoot length, dry biomass, and seed production ability of all four weeds species; however, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play ...

A large number of weeds are known to be associated with crops and causing economic losses. Weeds interfere with crops through competition and allelopathy. They produce secondary metabolites known as allelochemicals, which belong to numerous chemical classes such as phenolics, alkaloids, fatty acids, indoles, terpens etc. However, phenolics are the predominant class of allelochemicals. The allelochemicals release from weed plants takes place through leaf leachates, decomposition of plant residues, volatilization and root exudates. Weeds leave huge quantities of their residues in field and affect the associated, as well as succeeding crops, in various cropping systems. Liberation of allelochemicals from weeds affects the germination, stand establishment, growth, yield and physiology of crop plants. They cause substantial reduction in germination and growth of the crop plants by altering various physiological processes such as enzyme activity, protein synthesis, photosynthesis, respiration, cell division and enlargement, which ultimately leads to a significant reduction in crop yield. In crux, allelopathic weeds represent a potential threat for crop plants and cause economic losses.

Weed management has become increasingly important in the backdrop of sustainable crop production, uncertain climatic patterns and food security concerns in Pakistan. Due to diverse agro-climatic conditions, 267 weed species have been identified to be responsible for causing monetary loss worth 3 billion USD annually. Weed competition for resources, interference with crops, weed-related increased incidence of pests and diseases in different crops, and high management costs incurred in controlling weeds make weed management a critical task for the farmers. Moreover, herbicide resistant weeds, labor shortage, higher wages, weed population shifts, changing climatic optima, unavailability of proper and timely inputs, ever increasing threats of invasive weeds, lack of knowledge and training regarding herbicides, and the poor financial resources of the small land holders are major hurdles towards effective weed management in Pakistan. These multi-dimensional problems need holistic line of action with multi-disciplinary collaboration. Improved knowledge of weed ecology, biology, genetics and molecular biology is essential for developing sustainable weed control practices. Some advances are already commercialized, and others are in the process of development. Advancements like vision guided machines for site-specific weed management, recognition and application modules, development of air inclusion nozzles, nanoherbicides, water based formulations with fewer hydrocarbons, herbicide-resistant transgenic crops, robotics to monitor and spray weeds, decision support systems and predictive modeling can be adopted to foster modern weed management in the country. Various conventional weed management approaches like narrow row spacing, row orientation, increased crop density, use of cover crops, intercropping, development of weed-competitive crop cultivars, and their integration can help reduce herbicide input under a given scenario. There is dire need to establish regional weed research institutes under various cropping systems to carry out strategic and applied research in weed science. Innovative teaching and training practices are needed to tackle complex weed management challenges. Effective linkages between academia-research-industry-extension services could play a pivotal role to reframe technological advancements and legislation and to advocate innovations to the farmers. Capacity building, more research fund allocation, and reorienting educational system seem indispensable. Here, we have presented a broad review to summarize the current state of knowledge about the problems and prospects of sustainable weed management approaches in Pakistan. Advanced weed management approaches keeping in view the local agro-ecological conditions have also been discussed in this review to improve the scientific knowledge so that the discipline gets stronger and more focused than ever before.

Seed nutrients reserves have direct relationship with seed functional traits and influence offspring performance. Effects of plant density, foliage boron (B) nutrition and mepiquat chloride (MC) growth regulation on seed nutrients reserves, seed mass and production, and emergence and offspring growth traits of cotton were studied in two years field experiment. Seed nutrients reserves and seed mass were decreased at higher maternal plant density relative to lower plant density with concomitant decrease in emergence and offspring seedling growth. However, maternal foliage B nutrition and MC growth regulation enhanced seed nutrients reserves, seed mass, emergence and offspring seedling growth performance. There was a significant positive relationship between seed mass and seed nutrients reserves indicating that changes in nutrient availability/uptake in response to maternal ecological factors determine variation in seed functional traits. Nonetheless, seed mass was positively correlated with emergence percentage and negatively with emergence timing. Furthermore, variation in offspring seedling growth traits with seed mass indicated the significance of initial seed nutrients reserves for early seedling vigour and establishment. In conclusion, lower maternal plant density, B nutrition and MC growth regulation ensued in higher emergence and offspring seedling growth of cotton because of higher seed nutrient reserves and seed mass.

Crop row spacing adjustment and adjuvants have a significant role in decreasing herbicide cost and environmental damage by reducing herbicide application rate. A field study was conducted to assess the impact of two row spacing values and reduced herbicide rates along with adjuvant on weeds in maize in 2014 and 2015. The experiment consisted of atrazine plus mesotrione plus halosulfuran methyl (pre-mixed herbicide) at label rate (719.2 g a.i. ha-1); reduced rates of 75% (539.4 g a.i. ha-1) and 50% (359.6 g a.i. ha-1) alone and in combination with alkyl ether sulphate at 396.8 mL ha-1 as an adjuvant along with weedy check in maize sown at 60 and 75 cm row spacing. Alkyl ether sulphate increased weed control efficacy (13-35%) of the pre-mixed herbicide. Herbicide along with adjuvant provided effective weed control at 60 cm as compared to 75 cm apart sown maize. The most effective control of weeds, and increase in maize grain yield (33-45% as compared to non-treated control) and net income were obtained by the pre-mixed herbicide at 539.4 g a.i. ha-1 (75% of recommended rate) with adjuvant and pre-mixed herbicide at 719.2 g a.i. ha-1 (recommended dose) without adjuvant. The results revealed that the rate of pre-mixed herbicide can be reduced by up to 25% of the recommended field rate by the addition of alkyl ether sulphate as an adjuvant at 60 cm row spacing of maize to increase maize yield and net income. RESUMO: Nas culturas agrícolas, o espaçamento entrelinhas e os adjuvantes desempenham um papel importante para a redução do custo do herbicida e dos danos ambientais através da redução da dose dos herbicidas aplicados. Foi conduzido um estudo de campo para avaliar o impacto de dois espaçamentos entrelinhas e da redução das doses de herbicidas juntamente com o adjuvante em plantas daninhas em cultura de milho em 2014 e 2015. O experimento foi composto de atrazina, mesotriona e halossulfurom-metílico (herbicida pré-misturado) na dose recomendada (719,2 g i.a. ha-1); doses reduzidas de 75% (539,4 g i.a. ha-1) e 50% (359,6 g i.a. ha-1) isoladas e em combinação com alquil éter sulfato a 396,8 mL ha-1 como adjuvante, juntamente com capina em milho semeado com espaçamento entrelinhas de 60 e 75 cm. O alquil éter sulfato aumentou a eficácia do controle de plantas daninhas (13-35%) com o herbicida pré-misturado. O herbicida, juntamente com o adjuvante, resultou no controle eficaz de plantas daninhas com uso de espaçamento de 60 cm, em comparação com o milho semeado com espaçamento de 75 cm. O controle mais eficaz das plantas daninhas e o aumento do rendimento de grãos de milho (33-45% em comparação com o controle sem tratamento) e da renda líquida foram obtidos pelo herbicida pré-misturado a 539,4 g i.a. ha-1 (75% da dose recomendada) com o adjuvante e pelo herbicida pré-misturado a 719,2 g i.a. ha-1 (dose recomendada) sem o adjuvante. Os resultados revelaram que a dose de herbicida pré-misturado pode ser reduzida até 25% da taxa de campo recomendada através da adição de alquil éter sulfato como adjuvante com espaçamento de 60 cm para as culturas de milho a fim de aumentar o rendimento do milho e a renda líquida.

Seed nutrients reserves have direct relationship with seed functional traits and influence offspring performance. Effects of plant density, foliage boron (B) nutrition and mepiquat chloride (MC) growth regulation on seed nutrients reserves, seed mass and production, and emergence and offspring growth traits of cotton were studied in two years field experiment. Seed nutrients reserves and seed mass were decreased at higher maternal plant density relative to lower plant density with concomitant decrease in emergence and offspring seedling growth. However, maternal foliage B nutrition and MC growth regulation enhanced seed nutrients reserves, seed mass, emergence and offspring seedling growth performance. There was a significant positive relationship between seed mass and seed nutrients reserves indicating that changes in nutrient availability/uptake in response to maternal ecological factors determine variation in seed functional traits. Nonetheless, seed mass was positively correlated with emergence percentage and negatively with emergence timing. Furthermore, variation in offspring seedling growth traits with seed mass indicated the significance of initial seed nutrients reserves for early seedling vigour and establishment. In conclusion, lower maternal plant density, B nutrition and MC growth regulation ensued in higher emergence and offspring seedling growth of cotton because of higher seed nutrient reserves and seed mass.

Jabran, Khawar/0000-0001-8512-3330; WOS: 000436879200076 PubMed: 29691745 Plants in Brassica genus have been found to possess strong allelopathic potential. They may inhibit seed germination and emergence of subsequent crops following them in a rotation system. Series of laboratory and greenhouse experiments were conducted to determine the allelopathic impacts of Brassica napus L. against mung bean. We studied (1) the effects of aqueous extract (5%) of different plant parts (root, stem, leaf, flower, and whole plant) of B. napus, (2) the effects of leaf and flower extracts of B. napus at 0, 1, 2, 3, and 4% concentrations, and (3) the effect of residues of different B. napus plant parts and decomposition periods (0, 7, 14, and 21 days) on germination and seedling growth of mung bean. Various types of phenolics including quercitin, chlorogenic acid, p-coumeric acid, m-coumaric acid, benzoic acid, caffeic acid, syringic acid, vanillic acid, ferulic acid, cinamic acid, and gallic acid were identified in plant parts of B. napus. Among aqueous extracts of various plant parts, leaf and flower were found to have stronger inhibitory effects on germination and seedling growth traits of mung bean, higher concentrations were more toxic. The decomposition period changed the phtotoxic effect of residues, more inhibitory effect was shown at 14 days decomposition while decomposition for 21 days reduced inhibitory effect. The more total water-soluble phenolic was found in 5% (w/v) aqueous extract and 5% (w/w) residues of B. napus flowers at 14 days of decomposition (89.80 and 10.47 mg L-1), respectively. The strong inhibitory effects of B. napus should be managed when followed in rotation.

This study was conducted to explore the growth stimulating effect of foliage applied brassica water extract on growth and productivity of bread wheat (cv. Punjab 2011) at low and high fertilizer doses. The brassica water extract (5%) and the commercial growth regulator benzyl amino purine (BAP) (5 ppm) were applied alone and in combination at 30 and 45 days after sowing (DAS) under low fertilizer dose (125 kg ha-1 N and 90 kg ha-1 P) and high fertilizer doses (225 kg ha-1 N and 150 kg ha-1 P). Application of the brassica water extract (5%) significantly improved morphological traits such as crop growth rate, leaf elongation, leaf area index, plant height and number of productive tillers under both fertilizer regimes. Similarly, growth regulator benzyl amino purine (5 ppm) application enhanced the growth and yield components of wheat. However, maximum grain yield (6.20 t ha-1) was recorded with combined application of the brassica water extract (5%) and BAP (5 ppm) under the high fertilizer dose followed by individual application of the brassica water extract (5%) and BAP where 5.39 and 5.94 t ha-1 grain yields were recorded. Biological yield also showed an almost similar trend under the influence of the allelopathic water extract of brassica and BAP. Economic and marginal net benefits of 1521.6 and 237.0 USD ha-1 were respectively achieved with the application of the brassica water extract under the lower and higher fertilizer applications, respectively. The foliage applied 5% brassica water extract and BAP (5 ppm) was the most effective and had a stimulating impact on the growth and productivity of wheat. RESUMO: Este estudo foi realizado para investigar o efeito estimulador do extrato aquoso de plantas do gênero Brassica, sob aplicação foliar, no crescimento e na produtividade do trigo panificável (cv. Punjab 2011) em doses baixa e alta de fertilizantes. O extrato aquoso de Brassica (5%) e o regulador de crescimento benzilaminopurina (BAP) (5 ppm) foram aplicados isoladamente e combinados aos 30 e 45 dias após a semeadura (DAS) sob dose baixa de fertilizante (125 kg ha-1 N e 90 kg ha-1 P) e dose elevada de fertilizante (225 kg ha-1 N e 150 kg ha-1 P). A aplicação do extrato aquoso de Brassica (5%) melhorou de forma significativa as características morfológicas, como taxa de crescimento da cultura, alongamento da folha, índice de área foliar, altura das plantas e número de perfilhos produtivos, nos dois regimes de fertilizantes. Da mesma forma, a aplicação do regulador do crescimento benzil amino purina (5 ppm) gerou aumento nos componentes de crescimento e produção de trigo. No entanto, o rendimento máximo de grãos (6,20 t ha-1) foi registrado com a aplicação combinada do extrato aquoso de Brassica (5%) e BAP (5 ppm) sob dose elevada de fertilizante, seguido por aplicação individual de extrato aquoso de Brassica (5%) e BAP, tendo sido registrado rendimento de grãos de 5,39 e 5,94 t ha-1. O rendimento biológico também mostrou tendência quase semelhante sob a influência do efeito alelopático do extrato aquoso de Brassica e BAP. Foram obtidos benefícios econômicos líquidos e marginais de 1.521,6 e 237,0 USD ha-1 com a aplicação do extrato aquoso de Brassica nas doses inferior e superior de fertilizante, respectivamente. A aplicação foliar a 5% do extrato aquoso de Brassica e BAP (5 ppm) foi a mais eficaz e exerceu impacto estimulante sobre o crescimento e a produtividade do trigo.

In order to alleviate the drought adversities on maize (Zea mays L.)biomass accumulation and radiation useefficiency (RUE), a field study was conducted under drought stress levels of D1 = well-watered, D2 = droughtstress at blister stage, D3 = drought stress at blister and dough stages; and integrated nutrition levels, N0 =control, N1 = NPK, 125-60-62 kg ha-1, N2 = NPK, 125-60-62 kg ha-1 + FYM at 10 t ha-1, N3 = NPK, 125-60-62 kgha-1 + FYM at 15 t ha-1, N4 = NPK, 250-120-125 kg ha-1, N5 = NPK, 250-120-125 kg ha-1 + FYM at 10 t ha-1, N6 =NPK, 250-120-125 kg ha-1 + FYM at 15 t ha-1. Drought stress caused a significant decline in growth traits,interception of photosynthetically active radiation (PAR), RUE and finally biomass production. The highestleaf area index, leaf area duration, crop growth rate, net assimilation rate, interception of PAR and dry matteraccumulation was recorded in plants applied with NPK (250-120-125 kg ha-1) in combination with FYM (15 tha-1), whereas only NPK application did not significantly improve light interception and dry biomassproduction. Fraction of intercepted (Fi) radiation was significantly improved by integrated nutrientmanagement under well-watered as well as drought stress conditions. A substantial decrease in total drymatter and grain yield basis RUE was recorded from higher to lower plant nutrition rates, as the highest valueof RUE was found with treated plants of 250-120-125 kg NPK ha-1 + FYM at 15 t ha-1. Thus, our studydemonstrates that supplemental NPK with FYM is an effective strategy to boost the drought tolerance throughimproved RUE and biomass accumulation in maize., In order to alleviate the drought adversities on maize (Zea mays L.)biomass accumulation and radiation use efficiency (RUE), a field study was conducted under drought stress levels of D1 = well-watered, D2 = drought stress at blister stage, D3 = drought stress at blister and dough stages; and integrated nutrition levels, N0 = control, N1 = NPK, 125-60-62 kg ha-1, N2 = NPK, 125-60-62 kg ha-1 + FYM at 10 t ha-1, N3 = NPK, 125-60-62 kg ha-1 + FYM at 15 t ha-1, N4 = NPK, 250-120-125 kg ha-1, N5 = NPK, 250-120-125 kg ha-1 + FYM at 10 t ha-1, N6 = NPK, 250-120-125 kg ha-1 + FYM at 15 t ha-1. Drought stress caused a significant decline in growth traits, interception of photosynthetically active radiation (PAR), RUE and finally biomass production. The highest leaf area index, leaf area duration, crop growth rate, net assimilation rate, interception of PAR and dry matter accumulation was recorded in plants applied with NPK (250-120-125 kg ha-1) in combination with FYM (15 t ha-1), whereas only NPK application did not significantly improve light interception and dry biomass production. Fraction of intercepted (Fi) radiation was significantly improved by integrated nutrient management under well-watered as well as drought stress conditions. A substantial decrease in total dry matter and grain yield basis RUE was recorded from higher to lower plant nutrition rates, as the highest value of RUE was found with treated plants of 250-120-125 kg NPK ha-1 + FYM at 15 t ha-1. Thus, our study demonstrates that supplemental NPK with FYM is an effective strategy to boost the drought tolerance through improved RUE and biomass accumulation in maize.

Hormetic effects of herbicides at ultra-low doses have been proved against range of crop species, although available data of herbicides hormesis about the weeds growth is very limited. This study investigates the promotive effect of low doses of fenoxaprop-Pethyl on growth and seed production of littleseed canarygrass and wild oat. Pot experiments were conducted twice in Wire House at Agronomic Research Area, University of Agriculture, Faisalabad, during 2014-15. Seven different concentrations of fenoxaprop-P-ethyl [0, 1, 3, 6, 9, 12 and 15 g a.i. ha-1] were applied as post emergence herbicide at 3-4 leaves stage of the weeds. Results revealed that increase in growth occurred within first two weeks after spraying at fenoxaprop-P-ethyl doses 1, 3 and 6 g a.i. ha-1. More growth stimulation as compared to all other treatments was observed at fenoxaprop-P-ethyl dose 6 g a.i. ha-1. This initial increase in growth sustains with time up to the maturity of both weeds and positively influences seeds production ability. Up to 28% and 17% increase in number of seeds per plants were occurred in littleseed canarygrass and wild oat, respectively. Doses above 6 g a.i. ha-1 negatively affect the weeds growth and seed production ability. RESUMO Os efeitos horméticos dos herbicidas em doses ultrarreduzidas foram comprovados em relação a uma série de espécies de culturas, embora os dados disponíveis relativos à hormesis dos herbicidas em relação ao crescimento de plantas daninhas sejam bastante limitados. Este estudo investiga o efeito promotor de doses reduzidas de fenoxaprop-P-ethyl sobre o crescimento e a produção de sementes de erva-cabecinha e aveia-brava. Experimentos em vasos foram realizados duas vezes na Wire House at Agronomic Research Area, Universidade de Agricultura, Faisalabad, durante 2014-15. Sete concentrações diferentes de fenoxaprop-P-ethyl [0, 1, 3, 6, 9, 12 e 15 g i.a. ha-1] foram aplicadas como herbicidas pós-emergência com as plantas daninhas no estágio de 3-4 folhas. Os resultados revelaram que houve um aumento no crescimento dentro das duas primeiras semanas após a aspersão de fenoxaprop-P-ethyl nas doses de 1, 3 e 6 g i.a. ha-1. Um estímulo maior do crescimento em comparação com todos os outros tratamentos foi observado para o fenoxaprop-P-ethyl na dose de 6 g i.a. ha-1. Esse aumento inicial do crescimento é mantido com o tempo até a maturação de ambas as plantas daninhas e influencia positivamente a capacidade de produção das sementes. Um aumento de até 28% e 17% no número de sementes por planta ocorreu para a erva-cabecinha e a aveia-brava, respectivamente. Doses acima de 6 g i.a. ha-1 afetaram negativamente o crescimento das plantas daninhas e a capacidade de produção de sementes.

The allelopathic impact of aqueous extract (2.5 and 5%) and residues (2 and 4%) of five aquatic weeds namely Alternanthera philoxeroides, Alternanthera sessilis, Conyza stricta, Polygonum barbatum and Echinochloa crus-galli was investigated on the germination and early growth of wheat (Triticum aestivum). The aqueous extracts and residues of all tested weeds at different concentrations suppressed the germination/emergence percentage, mean germination/emergence time, and germination/emergence index and early seedling growth of wheat. Of the species tested, A. philoxeroides and A. sessilis showed the higher inhibition than C. stricta, P. barbatum and E. crus-galli. The results revealed that the inhibitory effect was proportional to the concentrations of the extracts and residues. Higher concentrations of extracts and residues had the stronger inhibitory effect. Aqueous extract caused more detrimental effect as compared to soil incorporated residues. Phytotoxins were identified as caffeic acid, chlorogenic acid, ferulic acid, 4-hydroxy-3methoxybenzoic acid, gallic acid, p-coumaric acid, m-coumaric acid, syringic acid and vanilic acid. It can be concluded that rice aquatic weeds contain allelopathic compounds in their tissues which may cause allelopathic effects on subsequent wheat crop in rice-wheat cropping.