Preliminary observations on tubers of yam (Dioscorea spp.) showed that there were increases in nematode populations during storage at ambient temperatures, whereas nematode counts were very low after storage at lower temperatures (12–13°C). Hot water treatments (50°C) for different lengths of time reduced the number of nematodes but damaged the tubers. Fumigation with methyl bromide, ethylene dibromide and hydrogen phosphide was not successful, as concentrations which reduced nematode numbers caused injury to the tubers. The effect of ethylene dibromide was not lasting.

Brassica carinata (an uncultivated species) was compared with other oilseed species already under cultivation in India, on irrigated and rainfed soils. B. carinata yielded very well in a wide range of environments partly because it had a large number of primary and secondary racemes. It also showed better environmental adaptation and substantial resistance to pests and disease.

A crop of broad beans was subjected to different water treatments with a view to finding the most economical irrigation policy. Increments in yield were obtained from the sixth to ninth irrigation, but the relative significance of each irrigation after the sixth was dependent upon whether irrigation water was saved during the vegetative and early flowering phase, or during the phase of pod development. The influence of the different water regimes on yield components and on some attributes of growth was studied.

Three effects of herbaceous weeds on the productivity of a bush fallow system cropped with maize, cassava and plantain were identified in four experiments carried out in Central Amazonian Peru. First, early weed control is needed to minimize crop yield reductions. Weeds reduce plantain raceme weight and days to flowering, but not cassava yield, if weeding is done early. Second, fallows must be long enough to reduce weed seed banks to levels tolerable to farmers. While fallows of between two and five years eliminate herbaceous weed biomass present at the beginning of the fallow, weed seed banks decline linearly through ten years of tree cover. Third, with successive clean-weedings to reduce weed competition, tree and shrub numbers and their proportion of total non-crop biomass decline, while the amount and proportion of herbaceous weeds increase. Tree and shrub regeneration is reduced by longer cropping periods, more frequent weedings, greater crop cover, and shorter fallow periods.

Ranking and scoring exercises are common in participatory research work, for example in determining farmer preferences for crop varieties, tree species or other commodities. However, they rarely involve eliciting opinions of many individual farmers so as to establish the repeatability of study findings. This paper demonstrates ways in which ranking of evaluation criteria can be combined with evaluation scores to produce generalizable results concerning farmers' overall preference for a set of bean (Phaseolus vulgaris) varieties. The use of weighted indices is explored. Results were found to be robust across all indices. However, farmer evaluations for yields did not correlate well with actual yields measured on their own plots. Farmers often gave high evaluation scores for yield performance of new bean varieties, even when they yielded quite poorly in plots in their own fields. Reasons for this are discussed.

Numerous technologies have contributed to the recent development of agriculture, especially the advancement in hyperspectral remote sensing (HRS) constituted a revolution in crop monitoring. The widespread use of HRS to obtain crop parameters suggests the need for a review of research advances in this area. HRS offers new theories and methods for studying crop parameters, but much work needs to be done both experimentally and theoretically before we can truly understand the physical and chemical processes that predict these crop parameters. The study focuses on the following elements: 1) The article provides a relatively comprehensive introduction to HRS and how it can be applied to crop monitoring; 2) Current state-of-the-art techniques are summarized and analyzed to inform further advances in crop monitoring; 3) Opportunities and challenges for crop monitoring applications using HRS are discussed, and future research is summarized. Finally, through a comprehensive discussion and analysis, the article proposes new directions for using HRS to study crop characteristics, such as new data mining techniques including deep learning provide opportunities for efficient processing of large amounts of HRS data; combining the temporal and dynamic characteristics of crop parameters and vegetation growth processes will greatly improve the accuracy of crop parameter detection and monitoring; multidata fusion and multiscale data assimilation will become HRS monitoring. Multidata fusion and multiscale data assimilation will become another research hotspot for HRS monitoring of crop parameters.

Production of cereal crops in sub-Saharan Africa is threatened by parasitic striga weeds and attack by stemborers and the invasive fall armyworm (FAW), compounded by increasing hot and dry conditions. A climate-smart push-pull technology (PPT) significantly reduces effects of these biotic challenges. To improve further resilience of the system to climate change, more adapted and suitable companion plants were identified and integrated in a new version of PPT, termed ‘third generation PPT’. Our study evaluates field performance and farmer opinions of this new version in comparison with the earlier version, climate-smart PPT, and farmers’ own practices of growing maize in controlling stemborers, FAW, and striga weeds. Trials were conducted across five locations in western Kenya for two cropping seasons in the year 2019 following a one-farm one-replicate completely randomized design. We assessed infestation on striga, stemborers, and FAW, and yield performance of the three cropping systems. We also sought the opinions of the hosting farmers through semi-structured questionnaires that were administered through individual interviews. Both PPT plots recorded significantly (P < 0.05) lower striga count, FAW, and stemborer damage, and higher grain yield than in plots that followed farmers’ own practices. There was no statistically significant difference between the two PPT plots except for stemborer damage for which the third generation PPT recorded higher damage than the climate-smart PPT. However, farmers preferred the third generation PPT for important traits possessed by its companion plants which their counterparts in climate-smart PPT are deficient. The cultivar Xaraes was rated as ‘very good’ for resistance to spider mites, biomass yield, and drought tolerance while Desmodium incanum was rated ‘very good’ for seed production and drought tolerance. The third generation PPT is based on companion crops that are more resilient to hot and dry conditions which are increasing rapidly in prevalence with climate change. This version therefore presents a better option to upscale the technology and meet different needs of farmers especially in arid and semi-arid conditions.

Surveys of the relationship between pests and diseases and crop sustainability in several areas of Kenya, Nigeria, and other regions of Africa indicate that the production of numerous crops has declined sharply as a result of major pest and disease outbreaks, and others are threatened with major decline because of a surge in virulence of an endemic pest or disease, the introduction of a virulent exotic pest or pathogen, or because a system of control used previously has collapsed. Many of the crops that have declined were already experiencing reduced economic demand. In other cases, crop sustainability has been preserved by vigorous farmer responses or by the intervention of national and international research institutions. Most pests and pathogens, however, remain within tolerable bounds most of the time, though this often requires the use of chemical or cultural controls, or the availability of adequate land to compensate for losses. As land availability declines, more strenuous management efforts may be needed to sustain productivity.

In many highly weathered soils of the humid tropics, crop exploitation of the subsoil environment is limited through acid soil infertility. Since the use of mechanical profile modification is often prohibitive, surface incorporation of soil amendments is often the only means available to rectify this problem. A field trial was established with sugarcane on a strongly Acidic Dystrophic Brown Dermosol (Oxic Humitropept) in 1978 to evaluate the effects of surface incorporated lime additions on yield and performance of sugarcane. Eighteen years after the establishment of this trial, significant responses in cane yield were still evident following a single application of 5 t lime ha−1 made in 1978, as well as repeated applications of 5 t ha−1 on three occasions over the past 18 years. Progressive reductions in exchangeable acidity were accompanied by increases in subsoil Ca2+ and Mg2+. Soil pH increased significantly to a depth of 100 cm, this being attributed to the formation of ion pairs with NO3 in the surface soil, the subsequent leaching of these complexes and the differential uptake of NO3 at depth by roots. The results from this long-term study indicate that surface incorporation of lime is an economically viable approach to the remediation of subsoil acidity on soils such as those studied, namely, those with a low inherent cation exchange capacity and anion exchange capacity.

Farmers who continue to grow old and obsolete varieties do not gain the benefits they could get from growing newer ones. Given the potential large scale of these foregone benefits, relatively few studies have examined the age of varieties that farmers grow. In three surveys, members of over 3300 households were interviewed to find the rice varieties they grew in 2008 and 2011 in 18 districts in the Terai, the low-altitude region of Nepal. This provided the first description of detailed geographical patterns of adoption of rice varieties and their ages that were repeated over time. There were large differences between district and individual varieties that showed specific geographical patterns of adoption. Such detailed knowledge on spatial diversity of varieties is invaluable for planning extension activities and developing breeding programmes, and cheaper ways than household surveys of collecting this information are discussed. Some of the factors considered important in determining this complex pattern of adoption were seed availability, growing environments that differed from east to west and the continued popularity of varieties once they had established markets. Rice diversity was low because a small number of rice varieties occupied large areas. In 2011, nine varieties covered at least 75% of the total rice area in western districts, just four in central districts and eight in eastern districts. Of these, most were released before 1995 resulting in a high average age of the predominant varieties – they always had an average age of over 20 years no matter which region or year was considered. Even though there were some large changes in varietal composition from 2008 to 2011, the average age of the predominant varieties remained almost the same. In a second paper in this series, we examine how these very low varietal replacement rates, that reduce yields and increase risk to farmers, can be accelerated using a participatory research for development approach called Informal Research and Development (IRD) (Joshi et al., 2012).

Experiments were conducted in both the greenhouse and the field on highly weathered (Orthic Ferralsol) soils to evaluate the effect of combining on-farm organic residues (chicken manure, farmyard manure, sugar bagasse) with Minjingu phosphate rock (MPR) on soil pH, extractable (available) and sorbed phosphorus (P), and to assess the cost benefit for maize production. The greenhouse study results indicated that, in the first eight weeks of incubation, soil pH increased linearly with increase in MPR rates and decreased thereafter. The available P also increased linearly. Chicken manure and sugar bagasse were most and least effective respectively in reducing P sorption, while there was a significant negative relationship between P adsorption maxima and extractable P. The field experiment data showed that the available P values increased significantly above the control in all the treatments where MPR and organic materials were applied separately or combined. Treatment effects on Langmuir sorption maxima (Smax) in the field were variable. An increase in Smax with an increase in MPR rates was noted. However, there was a positive relationship between Smax and available P (r = 0.52 to 0.69), suggesting the diversity of factors affecting the complex nature of P dynamics under field conditions. MPR applied alone in the first season gave a significant residual positive effect on maize grain yield for two additional seasons. The economic analysis revealed that a single application of chicken manure (2 t ha−1) combined with MPR at 60 kg P ha−1 gave the highest incremental net benefit equivalent to US$ 657 ha−1 during the three maize cropping seasons.

Achieving export growth in rice production from variable rainfed lowland rice ecosystems is at risk if depending on conventional breeding or genetic development alone. Sustained, long-term production requires building adaption capacity of smallholder farmers to better manage the challenges of seasonal climate variability and future climate change. Better understanding of the risks and constraints that farmers face in managing their current cropping system helps develop strategies for improving rice production in Cambodia. System models are now considered valuable assessment tools for evaluating cropping systems performance worldwide but require validation at the local level. This paper presents an evaluation of the APSIM-Oryza model for 15 Cambodian rice varieties under recommended practice. Data from a field experiment in 2011, conducted in a non-limiting water and nutrient environment, are used to calibrate varietal-specific coefficients and model input parameters. An independent dataset is then used to validate the model performance for a ‘real-world’ situation using on-farm data for six rice varieties planted in 54 farmer fields on 32 farms in two villages of Southeastern Cambodia. From this analysis, the APSIM-Oryza model is shown to be an acceptable tool for exploring the mismatch between current on-farm yields and potential production through yield gap analysis and the exploration of cropping system options for smallholder farmers to increase production, adapt to seasonal climate variability and be prepared for potential climate changes.

Continuous rice–wheat (RW) cropping in an area of 13.5 million ha with intensive tillage has resulted in over exploitation of resources, decline of the factor productivity, loss of soil fertility and biodiversity and decline of resource use efficiency in the Indo-Gangetic plains (IGPs) of South Asia. This has led to unsustainability of agriculture in the region. Replacement of a cereal-cereal system with a legume–cereal system may prove beneficial for long-term sustainability of the system. A field experiment was conducted with soybean–wheat (SW) rotation in the IGP of India during 2009–10 and 2010–11 to assess the suitability of conservation tillage versus conventional tillage (CT) and crop-establishment techniques, namely bed (B) planting versus flat (F) planting. The study revealed that the zero tillage (ZT) for soybean during rainy and for wheat during winter season either in flat or in bed system performed equally good with CT. The maximum system productivity (7.06 t ha−1 in 2009–10 and 8.48 t ha−1 in 2010–11) was obtained with combined application of wheat + soybean residue. The maximum net returns of ₹46.98 and ₹65.08 thousands and B:C ratio of 2.35 and 3.08 were recorded in the SW system with zero tillage-flat (ZT─F) during 2009–10 and 2010–11, respectively. The minimum energy of 64.67 and 63.01 ×103 MJ ha−1 was utilized as input energy with zero tillage-bed (ZT─B) while the maximum energy use efficiency of 4.10 and 5.14 was obtained with ZT─F and ZT─B for the SW system during 2009–10 and 2010–11 respectively. The gross output energy was maximum with wheat + soybean residue (241.6 and 265.7 ×103 MJ ha−1) contrary to this the net energy (194.4 and 213.4 ×103 MJ ha−1) and energy use efficiency (9.03 and 10.96) was maximum with control (no residue) in the SW system. In wheat there was 37.85% improvement in irrigation water use efficiency (WUE) in raised bed planting than flat planting and 28.57% of irrigation water was saved. The study suggested that ZT either bed or flat planting to both the crops can successfully adopted along with application wheat + soybean residue together with full recommended dose of NPK fertilizers to the system for improving productivity, profitability, soil health and sustainability of SW system in the IGPs of South Asia.

Earlier work has shown that, in cereals in general, grain yield (Y) and protein content (P) are strongly negatively related. It is shown here that the expected positive expected relationship between grain yield and protein yield also holds, with (YP) given approximately by YP = 0.141 + 0.0969 Y. All cereal breeding in which high protein content is desired therefore faces a compromise with grain yield.

Field studies of the dynamics of transformation and availability of applied phosphorus in a Vertisol cropped with rainfed cotton showed that phosphorus application increased available phosphorous in the soil. However, 70–80% of the phosphorus was fixed when more than 40 kg P2O5 ha−1 was applied. Maximum uptake of phosphorus by cotton occurred during the active growth period 40 to 80 days after germination, as reflected in a steep decline in the labile pool of available phosphorus in the soil. Over 50% of the total inorganic phosphorus occurred as Ca-P, which was the major contributor to the labile pool available to the cotton crop. The maximum response of cotton in terms of both dry matter and seed cotton and the maximum uptake of nitrogen, phosphorus and potash occurred when phosphorus was applied at 40 kg P2O5 ha−1. Phosphorus application increased the length, spread, volume and weight of roots.

Root measurements on three Malayan varieties of tapioca (high, medium and low-yielding clones) showed that the onset of tuberization brings about a slowing-down or cessation of growth in root length, but no changes in stem growth rate were associated with the onset of tuber growth. High yield was associated with high tuber weight rather than with tuber number, which could be related to the size of storage tissue cells formed by the root cambium. The process of tuberization in tapioca is discussed generally.

Salt (NaCl) and matric stress (polyethylene glycol; PEG 6000) impacts on germination were analysed in two rapeseed (Brassica napus var oleifera Del.) cultivars (Exagone: salt and water stress tolerant; Toccata: salt and water stress sensitive), which had the same imbibition kinetics when incubated in distilled water. Final germination percentage (G) and time to reach 50% G (T50) were affected either by 325 mM NaCl or −0.9 MPa PEG in Toccata but not in Exagone. Cultivars did not differ for protein concentration and protease activity in any germination condition; thus, protein metabolism seems not to be implicated in response to stress. Hydroxurea and cytochalasine-D inhibited germination in Toccata exposed to −0.9 MPa PEG but not in Exagone, suggesting that Exagone tolerance could be due to a lower amount of damaged DNA and lower requirement for DNA replication due to cell elongation rather than cell division for radicle elongation. Soluble sugars concentration increased in salt-stressed seeds from Exagone more than in Toccata and this could have allowed osmotic adjustment and therefore cell elongation despite the presence of external NaCl. Priming treatments with gibberellic acid, kinetin, NaCl and PEG hastened seed germination under control conditions but had no effect or even negative effects on germination under both salt and matric stresses.

The comparative stability of sorghum–cowpea intercropping and monocropping was assessed by determination of variances, regression against an environmental index, and probability of failure to achieve minimum levels of gross income. Significant differences between the cropping systems were not detected in any of the assessments though intercropping did have a lower probability of failure at the income levels for which risk was more than minimal. The failure of intercropping to show clearly greater stability in this study in which the environmental conditions were harsh provides a conflict with the conventional view.

The cotton–wheat production system (CWPS) occupies an important place in the agricultural economy of several South Asian countries. The instability of the CWPS has increased particularly during the post-transgenic hybrids phase mainly because of these hybrids calling for intensive crop management being cultivated under all situations, especially in resource-poor conditions leading to violent fluctuations during adverse years and thereby affecting the socio-economic status of these developing countries. A study was conducted to evaluate and quantify the effect of the two-tier intercropping of cotton and peanut with the substitution of a 25–50% recommended dose of nitrogen (RDN) of cotton by farmyard manure (FYM) on productivity, profitability and nitrogen economy in the CWPS at New Delhi during 2006–08. To quantify the residual effects of previous crops and their fertility levels, a succeeding crop of wheat was grown with varying rates of nitrogen, viz. 0, 50, 100 and 150 kg ha−1. Wheat equivalent productivity was significantly more with the inclusion of peanut in the CWPS (21–26%) with a high net return (US$288) than a pure stand of cotton in the CWPS. The substitution of 25% RDN of cotton by FYM being on par with no substitution recorded a higher wheat equivalent yield, nitrogen, phosphorus and potassium uptake, net return and nitrogen use efficiencies. Nitrogen economy in wheat was 22 kg ha−1 due to inclusion of peanut in the CWPS and 13 kg ha−1 due to substitution of the 25% RDN of cotton by FYM. The study suggested that for the success of the CWPS in South Asian countries, escalating prices of N fertilizers with environmental issues and the instability of transgenic hybrids can be overcome by using wider rows of cotton by peanut intercrop with the integrated use of both organic and inorganic sources of nitrogen.

The present study concerns identification of the most profitable and water and nitrogen use efficient best management practice (BMP) in a rice–wheat system using a combined approach of field experimentation and simulation. In the field study, two independent experiments, (1) effect of three transplanting/sowing dates, two cultivars and two irrigation regimes and (2) effect of four nitrogen (N) levels with four irrigation regimes, were conducted for two seasons of 2008–09 and 2009–10 at Punjab Agricultural University, Ludhiana, India. Integrating the treatments of the two independent field experiments, simulations were run with the CropSyst model. The BMP demonstrated was transplanting of rice on 20 June and sowing of wheat on 5 November, irrigation to rice at 4-day drainage period and to wheat at irrigation water depth/Pan–E (open pan evaporation) ratio of 0.9, and fertilizer N of 150 kg ha−1 to each crop for medium-duration varieties. This practice gave higher profit (35%), equivalent rice yield (16%), crop water productivity (15%), irrigation water productivity (51%), economic water productivity (34%) and economic N productivity (94%) than the existing practice by the farmers. The improvement in crop water productivity by shifting the transplanting/sowing date was due to reduction in soil water evaporation and increased transpiration and fertilizer N productivity through increased N uptake.