We aimed to assess the potential of the characterization of association among weed species as a tool to understand weed occurrence for further supporting long-term management programs. After a sequence of summer crops, which included irrigated rice and sorghum, the experimental area was submitted to subsoiling, limestone was applied, and ryegrass was planted in the winter season. Six months later, an ACCase-inhibitor herbicide was used to select only non-grassweed species. Field survey was carried out on 100 quadrats with 0.5-m width that were randomly sampled. Plant species were organized in 2 × 2 contingency tables. The results of the calculated chi-squares were compared to the respective tables, and results were presented as a paired chi-square matrix. The species–area curve was also obtained. The relative occurrence of species was determined by its frequency and presented as a wordcloud. The network analysis was obtained by using the Fruchterman–Reingold layout. The hypothesis of plant association aiming survival in arable fields was validated. The methodology of plant association based on the chi-square test was applicable to arable fields, where weed species (usually competitor plant types) occur in clusters. From a practical point of view, preference should be given to herbicides that are efficient on most species within a given cluster.

Accurate crop varietal identification is the backbone of any high-quality assessment of outcomes and impacts. Sweetpotato (Ipomoea batatas) varieties have important nutritional differences, and there is a strong interest to identify nutritionally superior varieties for dissemination. In agricultural household surveys, such information is often collected based on the farmer's self-report. In this article, we present the results of a data capture experiment on sweet potato varietal identification in southern Ethiopia. Three household-based methods of identifying varietal adoption are tested against the benchmark of DNA fingerprinting: (A) Elicitation from farmers with basic questions for the most widely planted variety; (B) Farmer elicitation on five sweet potato phenotypic attributes by showing a visual-aid protocol; and (C) Enumerator recording observations on five sweet potato phenotypic attributes using a visual-aid protocol and visiting the field. In total, 20% of farmers identified a variety as improved when in fact it was local and 19% identified a variety as local when it was in fact improved. The variety names given by farmers delivered inconsistent and inaccurate varietal identities. Visual-aid protocols employed in methods B and C were better than those in method A, but greatly underestimated the adoption estimates given by the DNA fingerprinting method. Our results suggest that estimating the adoption of improved varieties with methods based on farmer self-reports is questionable and point towards a wider use of DNA fingerprinting in adoption and impact assessments.

Little is known about the adaptability of mamey sapote (Pouteria sapota) to acidic soils high in aluminum (Al). A 2 year field study was conducted to determine the effects of various levels of soil Al on dry matter production, stem diameter and nutrient concentration in tissues of four cultivars of mamey sapote. Soil Al treatments were statistically different for all variables measured in the study. Cultivars and the year × cultivar interaction were not significant; therefore, results were averaged over cultivars and years. Increasing soil Al concentration from 3.5 to 7.8 cmol kg−1 resulted in an increase in total dry weight, but higher soil Al concentrations resulted in dry weight and stem diameter reductions. Increments in soil Al resulted in a significant reduction in the concentration of leaf, stem and root calcium. The Al concentration in leaf and stem tissues was not significantly affected with increments in soil Al, but there was a significant decline in the concentration of Al in root tissue suggesting that mamey sapote may exclude Al from roots.

Suitable fertilization is crucial for the sustainability of rice production and for the potential mitigation of global warming. The effects of fertilization on porewater nutrients and greenhouse-gas fluxes in cropland, however, remain poorly known. We studied the effects of no fertilization (control), standard fertilization and double fertilization on the concentrations of porewater nutrients, greenhouse-gas fluxes and emissions, and rice yield in a subtropical paddy in southeastern China. Double fertilization increased dissolved NH4+ in porewater. Mean CO2 and CH4 emissions were 13.5% and 7.4%, and 20.4% and 39.5% higher for the standard and double fertilizations, respectively, than the control. N2O depositions in soils were 61% and 101% higher for the standard and double fertilizations, respectively, than the control. The total global warming potentials (GWPs) for all emissions were 14.1% and 10.8% higher for the standard and double fertilizations, respectively than the control, with increasing contribution of CH4 with fertilization and a CO2 contribution > 85%. The total GWPs per unit yield were significantly higher for the standard and double fertilizations than the control by 7.3% and 10.9%, respectively. The two levels of fertilization did not significantly increase rice yield. Prior long-term fertilization in the paddy (about 20 years with annual doses of 95 kg N ha−1, 70 kg P2O5 ha−1 and 70 kg K2O ha−1) might have prevented these fertilizations from increasing the yield. However, fertilizations increased greenhouse-gas emissions. This situation is common in paddy fields in subtropical China, suggesting a saturation of soil nutrients and the necessity to review current fertilization management. These areas likely suffer from unnecessary nutrient leaching and excessive greenhouse-gas emissions. These results provide a scientific basis for continued research to identify an easy and optimal fertilization management solution.

Three upland rice species, viz. Oryza sativa, Oryza glaberrima and an O. sativa × O. glaberrima interspecific hybrid, were grown in Ghana, harvested, and field cured under open (wet) and within ventilated but rainproof containers (dry) conditions for 5 weeks. Seeds from both environments were assessed weekly for physical, physiological and pathological quality. The relationships between air temperature and relative humidity, and seed moisture content (MC) and water activity differed between curing environments but within curing environments, relationships between seed MC and water activity were comparable among species. Prolonged field curing resulted in structural damage evidenced by the formation of multiple cracks in the endosperm; these were more frequent in wet cured seeds. Diverse fungal species were isolated from wet (22 species) and dry (23 species) cured seeds with a number of soil-borne species in the wet environment. Curing environment did not influence levels of fungal infection in O. glaberrima seeds but dry curing was associated with higher levels of fungal infection in O. sativa and O. sativa × O. glaberrima. Seed germinability in all the three species was higher in the dry cured seeds although vigour was relatively lower than wet cured seeds. Field curing the seeds of these three species within a dry environment could potentially improve subsequent seed viability, aid in moisture management and minimize structural damage to the endosperm; however, research on how fungal infection could be curbed under such conditions is needed.

Nitrogen (N) losses greater than 40% in furrow-irrigated cropping systems are a common problem that substantially limits yields. Sustainable production methods are therefore required to reduce these losses and increase the yield under semi-arid conditions. A field trial was carried out to study the soil N dynamics and soil physicochemical properties in soils amended with organic manure (i.e. with poultry manure (PM), farmyard manure (FYM) and pressmud compost (PrM)). Soil N dynamics and properties were evaluated under different ridge to furrow ratios (1:1 and 2:1) as well as maize yield and profitability. When ridge to furrow ratio increased (2:1) in soils amended with PM, the inorganic and organic N status was increased and N losses were reduced. This strategy lowered soil pH, and maximized organic matter status and maize yield. The highest yield, net income and benefit–cost ratio were attained with 2:1 ridge to furrow ratio and PM amendment, being an alternative management for increasing maize productivity and profitability while improving nutrient use efficiency.

Root-knot nematodes represent a serious threat to world coffee production, especially Meloidogyne incognita and M. paranaensis. Most cultivars of Coffea arabica are highly susceptible to these parasites and cultivation in infested areas has only been possible with the use of resistant C. canephora rootstocks. In this research, three elite clones of C. canephora, selected in areas infested by M. incognita and M. paranaensis, were evaluated in controlled conditions to assess levels of resistance against two populations of M. paranaensis, four populations of M. incognita and a mixed population of both species. The three clones were resistant to both species, but CcK1 and CcR2 were considered most promising because their vegetative growth was not impaired by nematodes.

Agroforestry systems (AFS) can serve to decrease ecosystem carbon (C) losses caused by deforestation and inadequate soil management. Because of their shade tolerance, cacao plants are suitable to be grown in AFS, since they can be combined with other kinds of trees and shrubs. The potential for C sequestration in cacao farming systems depends on various factors, such as management practices, stand structure and plantation age. We compared conventionally and organically managed cacao monoculture systems (MCS) and AFS in Sara Ana (Bolivia) with respect to C stocks in plant biomass and to amounts of litterfall and pruning residues. The total aboveground C stocks of the AFS (26 Mg C ha−1) considerably exceeded those of the MCS (~7 Mg C ha−1), although the biomass of cacao trees was greater in the MCS compared to the AFS. Due to higher tree density, annual litterfall in the AFS (2.2 Mg C ha−1 year−1) substantially exceeded that in the MCS (1.2 Mg C ha−1 year−1). The amounts of C in pruning residues (2.6 Mg C ha−1 year−1 in MCS to 4.3 Mg C ha−1 year−1 in AFS) was more than twice those in the litterfall. Annual nitrogen (N) inputs to the soil through pruning residues of cacao and N-fixing trees were up to 10 times higher than the N inputs through external fertiliser application. We conclude that appropriate management of cacao AFS, involving the pruning of leguminous trees, will lead to increases in biomass, litter quantity and quality as well as soil C and N stocks. Thus, we recommend stimulating the expansion of well-managed AFS to improve soil fertility and enhance C sequestration in soils.

We investigated the occurrence and status of the leaf folder Cnaphalocrocis ruralis (Walker) (Lepidoptera: Crambidae) in accessions of Erianthus spp. maintained as a part of the world germplasm collection at the Research Center of ICAR-Sugarcane Breeding Institute, Kannur, Kerala State, India. The nature, pattern, extent and year-to-year variation in damage were examined and accessions categorized based on relative incidence. The larvae of C. ruralis caused characteristic injury by feeding on chlorophyll bearing tissues leading to the formation of white and transparent streaks on the leaf blade. The grown-up larvae folded the leaf longitudinally with the adaxial surface inside the fold and exposing the abaxial surface, the edges being held in place by bands of silk thread at regular intervals. The length of leaf folds varied from 2.6 to 27.0 cm with a mean of 9.1 cm, which roughly constituted 7.3% of the mean length of the leaf blade. Leaf length, leaf width and leaf area were not correlated with either the leaf fold length or the number of webs. However, the leaf fold length was positively correlated with the number of webs. Attack rates (infestation rate) on cane basis (up to 69.0%) were generally higher than the damage rates (intensity) on leaf basis (up to 50.0%); infestation index ranged between 0.0 and 13.7%. Correlations between infestation rate and intensity varied among the three study years. Non-parametric analysis indicated significant differences among the three years for percent of infested canes and infestation index but not percent of damaged leaves. All accessions showed C. ruralis incidence in at least one experimental year, indicating that none of the accessions tested was immune to its attack. When all 74 accessions were considered on the basis of infestation index, 85.1% were placed in low and moderate categories and only 14.9% in high incidence category. Within the accessions of Erianthus spp., leaf area was not related to infestation rate of cane or damage rate of leaves but positively related to infestation index. The dynamics of the leaf folder in the predominantly paddy ecosystem were discussed in the light of its first occurrence in Erianthus spp. accessions in India and the world.

Knowledge of agro-physiological traits associated with drought tolerance would be useful for developing breeding materials for drought-prone environments. This study was conducted (i) to estimate genetic variability among 25 durum wheat genotypes in response to drought based on grain yield and 15 agro-physiological traits in single and multi-year trials; and (ii) to compare genotypes on the basis of multiple investigated traits using genotype by trait (GT) biplot technique and then recommend possible selection strategies. We found large genetic differences among durum wheat genotypes for agro-physiological traits in response to drought stress within and between single years, which revealed good promise in their further exploitation for selection in durum wheat breeding program. High broad-sense heritability and expected genetic advance as percent of mean observed in plant height (90.8%; 52.7%), grain yield (53.6%, 23.5%) and relative water loss (47.2%, 41.3%), respectively, indicated a major role of additive gene action. The results showed that the performance of genotypes was influenced by the year. The traits with high consistence across years were heading date, plant height and peduncle length. The potential quantum efficiency of photosystem II (Fv/Fm) and thousand-kernel weight (TKW) were positively associated with grain yield, while heading date, plant height and canopy temperature (CT) were negatively associated with grain yield under the drought conditions. In conclusion, based on across-year analyses, Fv/Fm, TKW, heading date, plant height and CT are the most promising traits for indirect selection.

The increasing tropospheric ozone concentration [O3] strongly affects plant growth. However, the response of belowground processes in rice (Oryza sativa L.) systems to higher O3 is not well understood. The grain production, belowground biomass partitioning, root morphology and activity of rice (cv. Shanyou 63) were investigated in a free-air O3 enrichment platform at four key growth stages. Elevated O3 (EO3, 50% above the ambient O3) significantly decreased the grain yield and total biomass at the grain milky mature stage, root biomass at the tillering stage and root to shoot ratios (RRS) at the flowering and grain filling stages. The effects of EO3 on root morphology and activity varied among rice growth stage. EO3 significantly decreased root length, density, area, diameter and volume at the flowering stage, but EO3 significantly decreased various root morphological indices at the tillering, grain filling and milky mature stages. EO3 significantly increased the specific root respiration rate (root activity) and root respiration rate (autotrophic respiration) at grain filling and milky mature stages. Higher root autotrophic respiration and lower RRS in response to EO3 would reduce allocation of assimilated carbon to root growth, adversely affecting rice productivity. Our findings are critical for understanding the O3-induced impairment of belowground processes and carbon cycling in rice cropping systems and breeding of O3-tolerant cultivars under higher [O3] scenarios.