Highly weathered soils from humid tropics naturally have low contents of available potassium (K) to plants. Under these conditions, the K deprivation can change the equilibrium among cations in the soil and the nutritional status of some crops as soybean (Glycine max (L.) Merrill). A field experiment related to K fertilisation, spring soybean and diverse species of fall/winter crops, such as wheat (Triticum aestivum L.), corn (Zea mays L.), sunflower (Helianthus annuus L.) or oat (Avena strigosa L.), has been carried out in Southern Brazil since 1983. The K deprivation for 8 years reduced soybean grain yield and the K contents in soil and plant tissues. K extractants, such as Mehlich-1 and ion exchange resins, had diverse sensitivities with the variation in the K exchangeable contents induced by K rates. The increased soil K content after K fertilisation reduced calcium (Ca) and magnesium (Mg) contents in index leaves and altered its contents in the soil extracted by 1 mol L−1 KCl and ion exchange resins. Among the micronutrients, only B contents changed due to increased K rates, and had significant correlations with K and Ca contents in index leaves. The calculated Diagnosis and Recommendation Integrated System (DRIS) indices were compatible with soybean yield and K contents in soybean index leaves.

In experiments conducted in the Ord River Valley, North Western Australia, the extent of egg laying, larval numbers and grain damage from Heliothis armigera was studied with three sorghum varieties of different head densities. Total numbers of eggs laid were similar for each variety, larval infestation was highest on a very dense-headed variety Pickett 932045 and similar in the semi-dense headed RS610 and the open-headed E57 varieties. Greater losses per larva were estimated with varieties E57 and Pickett 932045 than for RS610, where lesser susceptibility was associated with ability to compensate, mainly by increased grain size, for grain loss. This paper reports the results of experiments at Kimberley Research Station to measure infestation and damage caused by H. armigera on three varieties of sorghum with head types ranging from dense to open, and the effectiveness of biological and chemical control practices are also discussed.

In tropical Africa, pepper (Capsicum spp.) is grown as a rainfed crop, and its production is limited by the long, hot growing season. Field experiments were conducted in Nigeria to evaluate the effects of cassava (Manihot esculenta) on the growth and yields of three pepper cultivars and gross returns in 2001–2003. In Experiment 1, pepper (cv. Sombo) was planted between rows of cassava cvs Idileru (PI), Odongbo (PO) and TMS 30572 (PT). In Experiment 2, pepper cvs Sombo, Tatase and Atarodo, were mixed with TMS 30572 (MS, MT or MA). The growth environment for the intercropped pepper differed from sole crops of pepper. Radiant energy reaching the soil surface, maximum diurnal soil and canopy temperatures, and weed growth were lower with intercropping, with the lowest values being observed in the PI and PT intercrops. Similarly, soil moisture content and the number of earthworm casts were greater with intercropping, with the highest values also occurring in the PI and PT intercrops. In both experiments, fresh fruit yields of pepper depended on the duration of harvest, the number of fruits per plant and the weight of fruits. In Experiment 1, although the number of fruits and fruit yield of cv. Sombo were greater in the sole crop (SP) than the PO intercrop, the fruit yields in the PI and PT intercrops were similar to those of the SP plot. In Experiment 2, the number of fruits and yield of intercropped pepper cvs Tatase, Sombo and Atarodo were 25–28 % higher, on average, than in pure stands. Cassava tuber yield was not affected by intercropped pepper in either experiment. Total gross returns were greater than growing either pepper or cassava in monoculture. Increased total gross returns in the intercrops were obtained in the PI and PT treatments and in the MS and MA treatments without a significant reduction in pepper fruit yield. By promoting early fruit set and harvest, and bearing in mind the cumulative gross returns, mixing pepper and cassava enhanced the value of the vegetable, as early fresh pepper fruits command a premium price. It is concluded that pepper can be grown between cassava rows to provide a suitable environment for growth, but that this depends on the cassava cultivar. Using the less tall early cassava cultivar, with a relatively moderate leaf area index in a mixture with pepper is therefore recommended.

Meeting the burgeoning global demand for both food and energy requires substantial yield increases through the efficient use of inputs like fertilizers. Prompted by the result of a soil survey expedition in the late 1950s, which signaled a widespread deficiency of nitrogen (N) and phosphorus (P), plant nutrition research in Ethiopia began in the 1960s, focusing on the response of prioritized cereals – tef (Eragrostis tef), wheat (Triticum aestivum), and maize (Zea mays) – to the application of N and P fertilizers. Nationwide on-farm trials conducted in the early 1970s led to a blanket recommendation of 64 kg N ha−1 and 20 kg P ha−1, irrespective of the crop and soil types, which were applied in the form of di-ammonium phosphate (18-46-0) and urea (46-0-0), respectively. Research conducted in the 1980s across agro-ecological and edaphic spectrum recommended 30–138 kg N ha−1 and 0–50 kg P ha−1, respectively. However, studies show that only 30–40% of the smallholder farmers use fertilizers at a rate less than recommended (on average at 37–40 kg ha−1). This rate reflects limited supply, high prices, and the low and declining crop response to fertilizers. As a result, cereal yields increased only 10% despite a fivefold increase in fertilizer application since the 1980s. Owing to the limited and declining crop response and the increased price of fertilizer in the 1990s, research on the integrated application of inorganic and organic sources of fertilizers was initiated. Although the integrated use resulted in increased yield and better economic benefits, it was not mainstreamed into the national agricultural extension system. The soil survey expedition that began in 2011 culminated in the mapping of the soil nutrient status using literature-based critical limits. The maps have persistently revealed the deficiency of N, P, potassium, sulfur, zinc, and boron across the surveyed areas. Despite the above efforts, the data sets generated through the soil surveys conducted at different times during the last half-century and the agronomic research during the same period have never been fully exploited. It is believed that the recent development in data mining and machine-learning approaches creates the opportunities to use the data sets in conjunction with other covariates in order to generate evidence that helps to make better decisions both at strategic and operational levels. The development of decision support tools based on such large datasets and analytical capacity is believed to facilitate better-informed decisions that lead to increased resource use efficiency and sustainability.

The native rhizobia capable of symbiosis with chickpea crops in the Turkish highlands were surveyed and estimates made of the numbers of bacteria and the nitrogen fixing efficiency of isolates of R. ciceri in symbiosis with an improved Turkish cultivar and a local landracc. Soils were collected from locations at elevations between 500 and 2200 m.

Native rhizobia specific to the local landrace were more abundant than those specific to the improved cultivar but nitrogen fixation efficiencies of all isolates were consistently poor. Agronomic research priorities must include the identification of strains of rhizobia symbiotically efficient and ecologically persistent in highland soils. Comprehensive trials with these strains as artificial inoculants on chickpeas are required throughout the region.

Biodiversidad en el Rhizobium ciceri

Pot experiments were used to test the effect of incorporating various organic materials in the soil on the nodulation of peas (Pisum sativum). Only farmyard manure gave a consistent increase in the number and weight of nodules, and also in plant growth, increases which were also produced by the aqueous extract of farmyard manure, although none of these increases were as large as those obtained by the addition of a combination of P and K fertilizers or activated vermiculite. Field beans (Vicia faba) and French beans (Phaseolus vulgaris) in general reacted in the same way as peas.

The Adaptive Research Planning Team in Luapula Province (ARPT-LP) is one of nine provincial teams in Zambia conducting farming systems research within the Research Branch of the Ministry of Agriculture and Water Development. ARPT-LP has been relatively successful in developing a partnership with farmers, involving them in both the planning and implementation of the team's research programme. This paper examines the formal and informal occasions on which farmers have been involved in the team's activities, with examples to illustrate how farmers' opinions have influenced decisions made by ARPT-LP. The factors which have influenced the frequency and quality of the scientists' interaction with farmers are discussed.

Factorial combinations of three daylengths (11, 12 and 15 h), warm and cool days (30° and 22° C) and warm and cool nights (18° and 10°C) were imposed on nodulated plants of three chickpea cultivars grown in pots in controlled environment growth cabinets. The treatments had large effects on growth, phenology and seed yield and no single environmental regime was optimal for all successive stages of development. Root growth and nodulation were extremely responsive to the environment experienced by the shoot. Conclusions are drawn on the potential contribution of these data to the development of empirical screening techniques suitable for large, segregating populations in field programmes devoted to the production of chickpea cultivars better adapted to their intended environments.

Three short duration and one long duration groundnut genotypes, grown either ‘sole’ or as intercrops (in 1:1 ratios of the short duration with the long duration genotypes), were compared in four trials. The intercrop treatments resulted in Land Equivalent Ratios (LERs) of up to 1.25 for pod yield and total biomass despite moderate or severe water deficits at the end of the season. Specific combinations of genotypes were necessary to maximize the LER. The results indicate there is scope for achieving greater productivity in environments with a variable season length by growing late and early genotypes together in an intercrop system.

Seedling vigor is important to help ensure good crop establishment. In direct-seeded rice, this is particularly relevant when soil conditions are marginal. In Asia, about one third of the area of rainfed rice is situated on unfavorable soils, many of which are low in plant available P. In such environments, as farmers tend to have few resources, options to overcome poor crop establishment should be low cost and preferably seed-based. The P content of seed depends on genotype and can be augmented by soaking seeds in a P-containing solution prior to seeding (P-priming). In addition, the presence of the Pup1 quantitative trait locus can reportedly confer tolerance to low soil P availability. We tested combinations of seed priming (unprimed control, water priming, P-priming), and inherent seed P concentrations in contrasting rice genotypes (DJ123, Sadri Tor Misri), and two near isogenic sister lines of IR74 with (+Pup1) and without (−Pup1) the Pup1 QTL. Treatment effects on germination were studied in Petri dishes, while seedling growth and P accumulation were assessed using pots with P deficient soil. Germination was less than 75% in seeds with low seed P content. Seed priming with both water and P enhanced germination and seedling growth. In plants growing from high P seeds, water priming outperformed P-priming. In Sadri Tor Misri with low seed P, we observed a tendency for better performance in some parameters when P-primed. While the presence of the Pup1 QTL in IR74 increased shoot biomass and total root length, these effects could be further enhanced by water priming. Combining genetic and seed management approaches may contribute to improved rice establishment in P deficient soils but its effectiveness depends on genotype and seed attributes.

In the hilly areas of eastern Gujarat, western Madhya Pradesh and southern Rajasthan, in western India, farmers are very resource-poor and cultivate small and fragmented land holdings. Maize is their main rainy season (kharif) cereal and it is grown as a rainfed crop in low-fertility fields, often on sloping land that is vulnerable to soil erosion. Its productivity is very low, averaging below 1 t ha−1. New farm technologies to increase this productivity have to be low cost to be attractive to farmers who have limited access to purchased inputs and few means to purchase them. From observations of local farming practices, intercropping of maize with legumes was identified as an attractive option because the only additional input needed is seed of the legume crop. Participatory research was conducted on intercropping of maize with improved varieties of horsegram (Macrotyloma uniflorum). Many farmers who tried this intercropping adopted it in subsequent years, while others preferred to grow the new horsegram varieties as a sole crop. Farmers reported that less weeding was required in the intercrop as the horsegram smothered weeds. All farmers used the dry stover from the horsegram as a fodder for their animals. Farmers used the whole seed as dal, which provided additional protein in their diet. Farmers also sold the grain, but it fetched a low price in the poorly developed market for horsegram. Previously intercropping had been tried with local landraces, but the acceptance of intercropping was higher with new varieties such as AK-42 that yielded over 60% more grain. Participatory trials in which only one entry was compared with the local variety did not show a difference between AK-21 and AK-42 as in all cases both were preferred over the local variety. When they were directly compared with each other, farmers' perceptions showed a significant preference for AK-42. Variety IVH-2 was found to be better than AK-42: it matured 15 days earlier, better matching the maturity of the maize, had superior grain quality and yielded about the same. The greater uptake of improved horsegram varieties for sole and intercropping is likely to be limited by the lack of seed supply.

Strategies for the implementation of integrated pest management (IPM) of cotton differ significantly depending on the agroecosystem and incidence of pests. Examples of successful IPM programmes from different countries, including those which involve insecticide treatments, are given in contrast to cases of inappropriate use of insecticides leading to pest resistance and crop failure. Inter-disciplinary research and farmer participation on a regional basis is necessary if IPM is to be implemented successfully.

Output:input ratios and apparent balances for nitrogen (N), phosphorus (P) and potassium (K) were measured in a rice-wheat system at Modipuram (29.4°N, 77.46°E, 237 m asl), India, under two planting densities (P1 = 200×200 mm for rice, 230 mm row spacing for wheat, and P2 = 200×100 mm for rice, 150 mm row spacing for wheat), and two levels of fertilizer NPK (100% F = recommended levels of fertilizer N, P and K for each crop, i.e. 120 kg N, 26 kg P and 33 kg K ha−1, and 150% F = 150% of the recommended levels) with and without 5 t ha−1 farmyard manure (M) to each crop. After two cycles of the rice-wheat rotation at a fixed site, N and K balances were negative for all treatments, but P balance was negative only in plots treated with P1 + 100% F treatment. The largest yield in the system, 15.7 t ha−1, was obtained in plots receiving P2 planting density with 150% F + M treatment, and the smallest (13 t ha−1) in plots of P1 planting density with 100% F treatment. In plots with the largest yield, total removal of NPK was 659 kg ha−1 (310 kg N, 62 kg P and 287 kg K ha−1), and in plots with the smallest yield, NPK removal was 411 kg ha−1 (188 kg N, 34 kg P and 189 kg K ha−1). At these nutrient uptakes, output:input ratios were 0.74 for N, 0.57 for P and 1.80 for K in plots receiving P2 + 150% F + M treatment, and 0.78 for N, 0.65 for P and 2.86 for K in plots receiving P1 + 100% F treatment.

A three-year study of the effects of sowing date, nitrogen application and seed rate on wheat showed that sowing in mid-October gave consistently greater grain yields than sowing in mid-September or mid-November because grains were larger and more numerous per head. Nitrogen increased yields but the effect decreased with later sowing. Nitrogen probably increased grain yield by increasing the number of ears, but this effect diminished with higher levels of nitrogen. Grain yield was only slightly influenced by seed rate, and the interaction of seed rate with sowing date or nitrogen was unimportant.

Changing the geometry of planting under irrigated conditions from the traditional pattern of regular rows (with plants equidistant from each other) into double rows (with plants arranged in row pairs) promoted plant competition. This resulted in a significant reduction in overall yield components of sorghum but a marked increase in shoot yields of striga. A better yield of sorghum was obtained in ridged plots than in flat plots, associated with less striga infestation and a slightly higher soil moisture content under the ridged plots.

Restriction fragment length polymorphisms (RFLPs) are genetic markers based on cloned molecules of DNA. Using RFLPs, scientists can construct high density genetic linkage maps and locate economically important genes. Once a gene for a valuable trait has been mapped with RFLPs, desirable genotypes can be selected using RFLPs rather than scoring for the trait itself. This is important when a trait is recessive, difficult to score, or obscured by other characters. RFLPs are particularly valuable in mapping genes controlling complex polygenic characters, including those fundamental to crop improvement. The first RFLP maps were developed in crop species primarily important in temperate countries. Now RFLP maps for major tropical and sub-tropical crop species are also being developed.

The relationship between climate, crop growth and crop yield is complicated. This study aimed to determine the ratio of CO2–C emission to grain yield, the field treatments were initiated in 2003, but the measurements for this analysis were collected during the summer maize-growing seasons of 2011 and 2012 in the North China Plain. The experiment showed that conventional tillage with straw application significantly increased grain yield and the ratio of CO2–C emission to grain yield of summer maize. The mean soil CO2–C emission rate with no tillage was significantly lower than that when conventional tillage was used; however, straw application significantly increased the soil CO2–C emission rate, irrespective of whether tillage was performed or not. This was mainly because straw application changed the soil total porosity and organic carbon content. In conclusion, the results of this study support the hypothesis that the ratio of CO2–C emission to grain yield in the North China Plain can be increased by straw application, whereas no tillage decreases this ratio.

Essential features are described of a computer programme, written in F.A.S., for the evaluation of 1 : 1 and 4 : 1 confidence limits of expected ‘twenty-day’ totals of rainfall. The paper deals briefly with the availability and utility of the programme to agricultural research workers in Africa.

A simple hand-held reflectometer was used to estimate the shoot dry matter of pearl millet (Pennisetum glaucum), groundnut (Arachis hypogaea), cowpea (Vigna unguiculata), weeds and grass swards non-destructively. While the instrument was able to predict shoot dry matter well for single, standing millet and cowpea plants and proved useful for a growth analysis of millet, its reliability was unsatisfactory for groundnut. For millet, the slope of two separate regressions between the difference of reflectance ratios and shoot dry matter, taken 10 days apart, was almost identical. This suggests a possible simplification in future crop growth models. The usefulness of the instrument for estimating dry matter in natural species mixtures such as weeds and grasses depended on the homogeneity of the mixture and the uniformity of their physiological state.

Medición de la biomasa utilizando la reflexión

Under controlled environment conditions rice variety IR8 was subjected to night temperatures of 15, 20 and 25°C during each of the three periods (a) sowing to floral initiation, (b) initiation to panicle emergence, and (c) panicle emergence to maturity, with day temperatures of 30°C throughout. Night temperatures of 15°C prevented floral initiation throughout the experiment, an effect partly overcome by transfer to higher temperatures after 102 days but not without yield loss. The optimum night temperature was 20–25°C, with some evidence of change of temperature effects, as distinct from the effect of actual temperature levels. As IR8 was developed under relatively stress-free conditions, its sensitivity to temperatures below 15°C may be greater than in varieties developed elsewhere.