The effects were evaluated of six methods and six durations of seed treatment on the germination of wild sunflower (Tithonia diversifolia) seeds. The treatments were as follows: (1) hot water at 80 °C, (2) hot water at 100 °C, (3) oven-drying at 80 °C, (4) oven-drying at 100 °C, (5) immersion in concentrated sulphuric acid and (6) immersion in 10% hydrogen peroxide. The durations were 0, 2.5, 5, 10, 15 and 20 min. Treatment with hot water at 80 or 100 °C for 11–14 min, and oven-drying at 100 °C for 20 min all resulted in more than 65% germination 10 d after treatment. Oven-drying at 80 °C, immersion in concentrated sulphuric acid and in 10% hydrogen peroxide resulted in less than 50% germination. Based on the higher cumulative germination, lower cost, and environmental concerns, hot water treatment at 80 or 100 °C for 11–15 min is recommended.

Soil moisture content and plant water status of young clonal tea plants were affected differently by five different types of mulches (black plastic, stone chippings and three types of grass) when compared with a control without mulch. During prolonged droughts, soil moisture content was generally highest under Napier grass and black plastic but any type of mulch was better than no mulch in conserving moisture to 90 cm depth. Tensiometer data at the onset of rains after an unusual prolonged dry season suggest that the infiltration was fastest under grass mulches. After four years of continuous application grass mulches had significantly most effect on water holding capacity, but induced shallow rooting systems, which made the mulched tea more susceptible to drought.

The fate of seed of six annual medics produced in spring 1987 and used in the pasture phase of cereal-pasture rotations was followed over four years. The medics were sown at low and high density, and seed set beyond 1987 was prevented by cultivation in 1988, and by herbicides in 1989 and 1990. The breakdown of hard seed was measured in the summer and autumn of each year, and the number of seedlings was counted after the first seasonal rains in the final three years. The survival of seeds buried at three depths was monitored. Seed of Medicago noeana lived longer than that of M. rotata and M. polymorpha. Survival of M. rigidula and M. truncatula seed was intermediate and there was no effect of planting density on survival. Breakdown of hard seed was least in the first year and increased in the second and third years. Within any year breakdown began in late summer or early autumn, beginning earlier as the seed aged. Seed burial enhanced germination in the year following seed set, depressed it in the second and third years, and had little effect in the fourth year. The net effect of seed burial on survival was therefore slight. The results suggest that the use of medics that have harder seeds than currently available cultivars, and medics in which germination is delayed until late in the autumn, will increase the sustainability and productivity of cereal-pasture rotations in semi-arid areas.

Dinámica de semilla de los Medicago spp anuales en Siria

Data from studies of growth and development, and response to plant density in common groundnut (Arachis hypogaea) cultivars were examined from published studies. Data were available from the humid tropics of Indonesia, the semi-arid tropics of north-west Australia and the humid coastal and inland elevated areas of north-east Australia. Temperature and irradiance played a major role in determining crop duration, individual plant size and partitioning of dry matter to pods across environments, and these plant characteristics provided the major determinants of pod yield and response to plant density. Crop duration was shortest in humid tropical and subtropical environments, with both high and low temperatures apparently delaying crop maturity. A relatively small individual plant size in humid tropical environments was due to a combination of low incident irradiance and short duration, with very high plant densities needed to maximize dry matter production. The progressive decline in harvest indices in more tropical environments was due to a decline in pod numbers per plant. Although increased plant density resulted in greater numbers of pod initials in the humid tropics, a high proportion of these pods did not contain developed seeds and pod yield at high densities remained relatively low at ≤2.5 t ha−1.

In this study, genotype by environment (G × E) interactions and phenotypic stability of resistance to Phytophthora infestans, the cause of late blight, were analysed in Peru for 13 potato genotypes, using additive main effects and multiplicative interaction (AMMI) analysis and Huehn's non-parametric test. The potato genotypes were tested in seven experiments over two years in the vicinity of Comas, Peru, an area used by the International Potato Center to screen for resistance to late blight. Results of the two analyses generally correlated and indicated that quantitative resistance to P. infestans was stable under field conditions for all the genotypes tested. The first two principal components (PCA1 and PCA2) of the AMMI analysis explained 54% of the G × E interaction sum of squares. A biplot of the two principal components demonstrated a strong year effect in the G × E interaction. By plotting yearly means of the relative area under the disease progress curve (rAUDPC), genotypes could be assigned to one of three resistance categories, resistant, moderately resistant or susceptible, but the need for a more readily applicable and truly quantitative scale for resistance was noted. Based on these studies, standards can be selected for use in screening in the area where they were tested. After further testing in other locations, a standard set drawn from these genotypes could be identified and a quantitative scale developed for evaluation of resistance under short day conditions.

The genus Phaseolus as currently recognized contains four pulses: common bean (P. vulgaris), runner bean (P. coccineus), lima bean (P. lunatus) and tepary bean (P. acutifolius). Although these all have their origins in tropical and sub-tropical latitudes, they have evolved in different ecological zones. The runner bean has evolved at higher altitudes, the common bean at intermediate levels and the lima bean at lower altitudes. The tepary has a specialized desert-annual life-form. The occurrence of day neutral genotypes in all species has permitted their spread into cool and worm temperate zones (the common and runner beans) and the warm temperate zone (lima bean). It is possible therefore to grow one or other Phaseolus species in most areas of the world where cultivation can be practised. The common bean has evolved the widest range of growth forms, seed and pod sizes, pod forms and textures, and seed and pod colors. World-wide an enormous primary gene pool has been produced. The common bean pool is the secondary gene pool for the runner bean and vice versa, since partially fertile interspecific species produce sterile or inviable F1 hybrids so that potential for interspecific gene transfer is limited. Thus no known secondary gene pools exist for Phaseolus species other than P. vulgaris and P. coccineus.

The uptake of urea fertilizer (NDFF), applied with 150 kg nitrogen (N) ha−1, topdressed in five splits of 30 kg N ha−1 (30 N) each at 7, 26, 45, 70 and 83 days after transplanting (DAT) of rice (Oryza sativa L.), was investigated in an improved (Khangma Maap, KM) and a traditional (Janam, JN) cultivar in Bhutan highlands, using enriched 15N stable isotope. The treatments were arranged in a split–split plot design, with N fertilizer levels as main plots, cultivars as subplots and topdressing treatments as sub-subplots, with all the sub-subplots receiving the same dose except different timing of one split of enriched 15N to determine partial N fertilize use efficiency at each split dose. Although cultivar differences were not recorded in soil N accumulation and in total dry matter N, KM produced 21% higher grain yields compared to JN due to higher grain harvest index and partial factor productivity of N. Irrespective of the cultivars, topdressing timing had significant effects on NDFF, with highest mean N recovery (REN) of 29% of applied 30 N at 45 DAT during active tillering stage, resulting in mean NDFF total (grain + straw) uptake of 8.71 kg N ha−1 compared to least effective topdressing timing at 7 DAT with mean REN of 12% and NDFF total of 3.51 kg N ha−1. In similarity to topdressing at 45 DAT, topdressing at 70 DAT (panicle initiation stage) was equally effective with mean REN of 27% across the cultivars. Hence, fertilizer N topdressing recommendations that combine use of improved cultivars with N applications timed to coincide with maximum crop demand at 45 and 70 DAT, could enhance N fertilizer use efficiency for increased rice yields as well as reduce N losses downstream, which can cause adverse off-site environmental effects.

Agronomists have increasingly conducted experiments on-farm, in an attempt to increase the wider applicability (external validity) of their experimental findings and their relevance for agricultural development. This review assesses the way in which on-farm experimental studies address the scope or generalisability of their findings when based on a limited number of farms. A central question is how on-farm studies define the environment or research population in which the on-farm trial findings are valid, or are valuable for. Such an assessment is, of course, conditional on the (internal) validity of the experimental findings. We therefore first analyse how authors of on-farm experimental studies describe the factors that may shape experimental outcomes. As agronomic experiments often use ‘yield’ as dependent variable to assess treatment effects, we developed a procedure to score studies on their descriptions of yield-determining factors. Although experimental validity principally rests upon the reproducibility of the experiment and its findings, we found that on the basis of the information provided in published on-farm experimental studies, it is often difficult or impossible to reproduce the experimental design. Nutrient management, weed management and crop information are best described, whereas land preparation, field history and management of pests and water are rarely described. Further, on-farm experimental studies often compare treatments to a ‘farmer practice’ reference or control treatment which is assumed to be widely and uniformly practiced and known to the reader. The wider applicability or external validity is often poorly addressed in the reviewed studies. Most do not explicitly define the research population and/or environment in which (they expect) the experimental findings to work. Academic textbooks on agronomic experimentation are remarkably silent on both the internal and external validity of on-farm experimentation. We therefore argue for more systematic investigations and descriptions of the research population and settings to which on-farm experimental studies seek to generalise their findings.

Trials in Kenya have shown that yields of tea clones can be increased significantly by grafting onto suitable rootstocks, with the best combinations giving profitable yield increases compared to straight cuttings. However, stock × scion interactions were significant, and not all clones gave useful responses to grafting even onto the best rootstocks, so combinations must be tested individually before commercial planting is considered. The effect of grafting was to increase the number of shoots harvested, with little change in mean shoot weight. Grafting had little or no effect on quality of the tea produced. Attempts to find a method of identifying good rootstocks without testing them in grafting trials were inconclusive.

Yields of intercropped cotton and groundnuts grown on alternate ridges 75 cm apart were compared in areas of high (more than 1000 mm a year) and low (less than 800 mm a year) rainfall and in rainy seasons with a low and high frequency of drought periods. There was no advantage from intercropping in the low rainfall area but in the high rainfall area land equivalent ratios of about 1.4 were obtained, confirming that intercropping is more suited to wet conditions. These high land equivalent ratios were associated with enhanced yields per plant in the cotton and unsuppressed yields per plant in the groundnuts, suggesting that a crop such as cotton, which both tolerates a wide range of population density and has a late-developing leaf canopy, may be particularly well suited to intercropping.

Cultivo simultáneo de algodón y chufa en zonas con altas y bajas precipitaciones en el este de Zambia

Two field experiments were conducted to evaluate the efficiency of rate, mode and time of application of manganese sulphate to irrigated wheat on manganese-deficient loamy sand (Ustipsamments) soils recently brought under rice. A significant increase in manganese uptake by wheat and marked increases in wheat grain and straw yields occurred following both soil (5, 10 and 20 kg Mn ha-1) and foliar (0.5, 1.0 and 2.0% MnSO4 solution) application of manganese, but foliar application was more effective. A series of sprays initiated before the wheat was first irrigated (26 days after sowing) gave significantly better results than application begun after the first irrigation (32 days after sowing); four sprays of 0.5% MnSO4 solution produced the largest grain yield, followed by three of a 1% solution.

Long-term tillage and fertilizer experiments were conducted in rice in kharif followed by lentil in dry subhumid Inceptisols at Varanasi and Faizabad; horse gram at Phulbani and linseed at Ranchi in moist subhumid Alfisols in rabi during 2001 to 2010. The study was conducted to assess the effect of conventional tillage (CT), low tillage + interculture (LT1) and low tillage + herbicide (LT2) together with 100% N (organic) (F1), 50% N (organic) + 50% N (inorganic) (F2) and 100% N (inorganic) (F3) on productivity, profitability, rainwater and energy use efficiencies. The results at Varanasi revealed that CT was superior with mean yield of 2389 kg ha−1, while F1 was superior with 2378 kg ha−1 in rice. At Faizabad, CT was superior with mean rice yield of 1851 kg ha−1 and lentil yield of 977 kg ha−1, while F1 was superior with 1704 and 993 kg ha−1 of rice and lentil, respectively. At Phulbani, F2 was superior with rice yield of 1170 kg ha−1. At Ranchi, F2 with rice yield of 986 kg ha−1 and F3 with linseed yield of 224 kg ha−1 were superior. The regression model of crop seasonal rainfall and yield deviations indicated an increasing trend in rice yield over mean (positive deviation) with increase in rainfall at all locations; while a decreasing trend (negative deviation) was found for lentil at Faizabad, horse gram at Phulbani and linseed at Ranchi. Based on economic analysis, CTF1 at Varanasi and Faizabad, CTF2 at Phulbani and LT2F2 at Ranchi were superior.

Green manures (GM) as an alternative to inorganic fertilizer offer considerable potential as a source of plant nutrients and organic matter (OM). Hence, field experiments were carried out during 2015 and 2016 cropping seasons to compare impacts of GM and NPK (15:15:15) fertilizer on soil properties, growth, fruit yield, mineral, lycopene and vitamin C contents of tomato (Lycopersicon esculentum Mill). GMs were composed by green tender stems and leaves of pawpaw (Carica papaya L.), neem (Azadirachta indica A. Juss.), moringa (Moringa oleifera Lam.) or gliricidia (Gliricidia sepium (Jacq.) Kunth ex Walp.) and applied at 5 Mg ha−1, whereas NPK was applied at 300 kg ha−1 and there was a no fertilizer plot (control). Application of GMs reduced soil bulk density and increased soil OM, N, P, K, Ca, Mg, growth, number of fruits and fruit yield of tomato compared with the control. NPK fertilizer had no effect on soil bulk density and soil OM, but it increased soil fertility and tomato yield as compared with the control. When comparing treatments, the highest tomato yield and best cost:benefit ratio were obtained with gliricidia as GM. The GMs and NPK fertilizer increased mineral, lycopene and vitamin C contents in tomato fruits and the highest K, Ca, Fe, Zn, Cu, lycopene and vitamin C contents in tomato fruits were found with moringa as GM. Our results revealed that GM has potential to improve soil properties, tomato yield and quality, being an alternative for cropping management.

On-farm nutrient management practices were evaluated in the irrigated rice-wheat cropping system (RWCS) in northwestern India. Large farmers used comparatively higher doses of nutrients than small and medium farmers for both rice and wheat crops. On average, a field is treated with organic manure after every 15 years for rice and 53 years for wheat. Nitrogen use was generally more than the recommended dose for both crops. Phosphorus use in wheat was nearly as per recommendation, while in rice it was below the recommended dose. Potassium use was almost nil; however, the use of Zn (particularly in rice) is becoming common. Use of biofertilizers was negligible. Overall, farmers applied higher doses of organic manures, K, Zn and biofertilizers in rice than wheat, and there was increasing trend in their use with increase in the size of land holdings. Grain yield increased significantly with increase in the size of land holding in rice but remained almost same in wheat. This study generated comprehensive data on nutrient use pattern in the RWCS, thus providing necessary input to researchers, planners and developmental agencies who wish to enhance food security.

Conflict is the most common cause of food insecurity. Foreign aid to countries emerging from conflict often allows a funded but brief window for the confirmation-testing and diffusion of agricultural innovation in affected areas. This paper asks the question: what lessons has agricultural research learned through its involvement in this process in countries emerging from conflict? Drawing on experience from Afghanistan and other countries, this paper documents some cases in which it has been possible to inject an element of simple hypothesis testing, often in farmer-managed trials, into post-conflict plans leading to useful lessons. Agricultural researchers need to be cognizant of this approach so that the practice becomes more widely used and lessons recorded for future use.

Different fruit thinning methods were tested on ‘Sensation’ mango trees over two seasons in a trial conducted in Northern Province, South Africa. The objective of the study was to select the best thinning intensity and method based on different parameters. Thinning was carried out in October prior to the occurrence of excessive natural fruit drop. When fruits were thinned to one and two fruits per panicle, fruit number, weight and yield per tree at harvest were all increased. When 50% of the panicles were thinned there was an increase in the fruit retention potential of the trees as well as in the size and quality of the fruit produced. Large fruits were, however, prone to certain physiological problems. Chemical thinning with Corasil.E produced very small fruits with an increased percentage of ‘mules’ (fruit without seed). Trees subjected to severe thinning intensities showed earlier recovery of starch reserves and better vegetative growth than the control.

Erosion trials under natural rainfall were conducted at two locations in the Andean hillsides of south-west Colombia on moderate slopes. Sediment-bound losses of seven cassava (Manihot esculenta) cropping systems per cropping period ranged from 26 to 1726 kg ha−1 for organic matter, 0.9 to 65.5 kg ha−1 for total nitrogen, 0.03 to 2.1 kg ha−1 for exchangeable magnesium, 0.04 to 2.8 kg ha−1 forexchangeable potassium and 0.004 to 0.8 kg ha−1 for Bray-II phosphorus. Runoff water contributed substantially to total available potassium, magnesium and phosphorus losses. Concentrations of soluble phosphorus in runoff water from heavily eroded continuously clean-tilled fallow plots were slightly higher than from cropped and fertilized plots. Enrichment ratios for sediments from these highly aggregated Inceptisols were low. Sand-sized particles were selectively removed by water erosion. The higher proportion of nutrient losses with run-off water in our study stressed the importance of runoff control along with attempts to control soil losses and thus diminish both nutrient losses and surface water eutrophication.

Increasing plant density in maize from 8 to 32 plants/m2, without irrigation, had little effect on the time of ear primordia differentiation but delayed the time of silking (by up to 16 days), reduced the potential grain sites available for pollination and the number of grains pollinated, and increased grain abortion during the grain fill period. In cv LG11 sufficient fertile ears were retained to maintain grain yield throughout the wide range in density, whereas yield fell in Anjou 210 due to barrenness after silking, which was the major factor responsible for the intolerance of this variety to high density. However, in a variety such as Anjou 210, which has a tendency to barrenness under stress, the grain content of the end product would not be affected at the plant densities normally used for maize silage.

Some agronomic, economic and ecological aspects of an agroforestry system combining Grevillea robusta trees, bananas (Musa spp.) and beans (Phaseolus vulgaris) were studied in the subhumid highlands of Burundi. Three densities of G. robusta, 208, 313 and 625  trees  ha−1 were interplanted in plots of bananas, beans and a banana–bean mixture. When G. robusta was interplanted with bananas, the tree had a positive effect on banana yield with maximum yield occurring at 300  trees  ha−1. In the presence of beans, banana yield was not influenced by the densities of the tree. Under low fertility regimes, the yields of beans interplanted with G. robusta were equal to or greater than those of the no-tree plots. Maximum bean yields were observed at between 283 and 295  trees  ha−1, representing a 25–135% yield increase above the no-tree control. When soil fertility was raised by the application of fertilizers, bean yields declined with an increasing density of G. robusta. Three years after planting, the growth of G. robusta was not affected by tree density. Mean height and mean basal diameter were 7.1   m and 13.2   cm respectively. Below ground competition between beans on the one hand, and bananas or bananas and G. robusta on the other, was more important than competition for light. Compared with the crops alone treatments, cumulative net present values of tree plots improved from being negative in the first year to being positive in the third year. Net present value was highest in two of three instances when the density of G. robusta was 625  trees  ha−1. A multistrata arrangement of bananas and beans with G. robusta is viable for the low input agriculture system of the highlands of Burundi.

Although triple cropping in inland valleys of Nigeria is technically feasible, the third crop between the main crop and dry season non-rice crop has been considered not to be economically viable because of poor crop establishment due to soil inundation. The identification of an appropriate technology with low input, such as ratooning, would allow this niche to be utilized. Field experiments were conducted at the University of Agriculture, Abeokuta, Nigeria in 2007–2008 and 2008–2009 cropping seasons to evaluate the performance of the main and ratooned crops of lowland NERICA (New Rice for Africa) rice (Oryza sativa L.) varieties in a lowland rice–ratooned rice–fluted pumpkin (Telfairia occidentalis Hook F.) sequence. The experiment was laid out in a randomized complete block design with three replicates. The lowland rice varieties used were NERICA-L 19, NERICA-L 20, NERICA-L 22, NERICA-L 24, OFADA, NERICA-L 26, NERICA-L 41, NERICA-L 42, NERICA-L 44 and NERICA-L 47. The grain yield of the main rice crop ranged from 5.0 to 7.3 t ha−1 in 2007–2008 cropping season and from 4.1 to 9.1 t ha−1 in 2008–2009. The ratooned rice had a grain yield of 1.0–4.7 t ha−1 in 2007–2008 and 1.2–3.4 t ha−1 in 2008–2009. The total grain yield obtained in 2007–2008 from the main and ratooned rice crops in seven months was 6.7–11.6 t ha−1, while in 2008–2009 it was 5.3–2.6 t ha−1. The fresh leaf yield of fluted pumpkin ranged from 14.6 to 16.9 t ha−1 in 2007–2008 and from 18.3 to 19.8 t ha−1 in 2008–2009, similar to previously reported rainy season unfertilized yields. Thus, a ratooned rice crop appears to be a feasible technology capable of boosting rice production and consequently increasing the overall productivity of the inland valley in a rice–rice–vegetable cropping sequence.