The potential yield of improved maize varieties usually cannot be fully realised mainly due to inappropriate soil nutrient management practices in most parts of Ethiopia. Site-specific fertiliser recommendations are rarely used in the farming systems of Ethiopia. There is also a lack of data to develop or validate decision support tools for targeting specific crop production. A study was conducted for three consecutive rainy seasons (2016–2018) in the maize belt of the north-western parts of the Amhara National Regional State of Ethiopia. The objectives were to obtain the maximum achievable yield potential of maize, determine the most yield-limiting nutrients and create a database of maize responses to applied nutrients so that decision support tools could be developed for the study areas. Treatments were individual nutrients (nitrogen (N), phosphorus (P) and potassium (K)) and combinations of the three. In some treatments, NPK was also combined with sulphur, zinc, lime and compost. Two hybrid maize varieties (BH-540 and BH-660) adaptable to the study areas were used. BH-540 was used for the Mecha district, while BH-660 was used for the south Achefer, Jabitahnan–Burrie–Womberma districts. Maize yield increased by more than 50% due to fertiliser applications compared to without fertiliser. The study showed that the possibility of increasing maize productivity to more than 12 t ha-1 for the study sites. The most yield-limiting nutrient in the study sites was N, followed by P; K was not a yield limiting. Without N the yield of both varieties was non-significant from the control (without added nutrients). Maize grain yield did not respond to application of lime, compost, zinc and sulphur. The result also showed very high variability across sites, indicating that it is important for policymakers, farmers and investors to consider site-specific fertiliser recommendations. Finally, a database containing intensive plant response to NPK for maize was generated and could be used as input in site-specific decision support tools development.

Farm mechanization promises to help raise labor productivity and reduce the heavy toil of farming on the world’s millions of smallholder farms, hence contributing to socioeconomic development in the Global South, in particular in Africa. While mechanization is therefore high on the African development agenda, there are heavy – at times dogmatic – debates on which technological pathway toward farm mechanization – animal traction, two-wheel tractors, and four-wheel tractors – should be supported by African governments and development partners. One discussion area relates to the future of animal traction. Proponents see a continued scope for the use of draught animals, whereas opponents see animal traction as old-fashioned and see a potential to leapfrog this mechanization stage. There are also debates on the potential of two-wheel tractors, with proponents arguing that such walk-behind tractors are more affordable and suitable for smallholder farmers, and opponents believing that such tractors lack efficiency and power and still come with a high drudgery. This paper argues that there are no blueprint answers on which technological pathway is ‘best’ but only answers on which one ‘best fits’ the respective conditions. Based on this premise, this paper introduces a ‘best-fit’ framework that allows for assessing the comparative advantages and disadvantages of the three technological pathways in different agroecological and socioeconomic conditions. The results suggest that all three forms of mechanization are associated with areas where they ‘best fit’. All three farm mechanization pathways hinge on public policies and investments to create an enabling environment for private markets, as, ultimately, innovation processes should be market driven. The ‘best-fit’ framework enables governments and development partners to focus efforts to support farm mechanization on solutions that ‘best fit’ their country’s farming systems and not on those that are politically most attractive, thereby contributing to sustainable agricultural mechanization and development.

Nitrogen fixation by leguminous trees such as sesbania (Sesbania sesban) in acid soils is limited by aluminium (Al) toxicity and phosphorus (P) deficiency. We screened 214 East African sesbania accessions for Al toxicity tolerance, P use efficiency and sesbania–rhizobia symbiosis. Aluminium toxicity tolerance or sensitivity was measured by the relative root elongation index. Highly Al tolerant and sensitive accessions were screened for P use efficiency. Highly P use efficient and Al sensitive accessions were assessed for symbiotic effectiveness with acid tolerant rhizobia. Eighty-eight per cent of the accessions were Al toxicity tolerant. High Al levels reduced shoot P content by 88% and total dry matter (TDM) by 83%. P addition increased shoot P content and TDM. Rhizobia inoculation increased nodulation by 28–82%, shoot N content by 28–45% and TDM by 15–34% in the low rhizobia density acid soil of Bumala, Kenya. P use efficient accessions had higher nodulation, shoot N content and TDM in the ranges 32–70, 20–52 and 22–36%, respectively, compared to sensitive genotypes. The combination of sesbania accession (SSUG10) and rhizobia strain ASs48 was superior in shoot N accumulation. Inoculation of P use efficient germplasm with acid tolerant rhizobia can improve N-rich biomass accumulation suitable for N replenishment in acid soils.

Results are reported from experiments with nitrogen and potash fertilizers in irrigated Rhodes grass (Chloris gayana), into which annual winter legumes, e.g. berseem (Trifolium alexandrinum) and vetch (Vicia sativa) were overseeded. The experiments were carried out over a three year period on a sandy loam soil at Bet Dagan Experimental Farm, Israel. Ammonium sulphate, applied in equal split rates of up to 384 lb N per acre, linearly increased dry matter yields of Rhodes grass, and the increase of yield proportionally increased the uptake of K by harvest. The K content of the dry matter decreased with increasing nitrogen fertilization to 0·47 per cent which, however, was still found sufficient for maintaining maximum production of Rhodes grass. The yield of annual winter legumes decreased proportionally to the amount of nitrogen fertilizer applied during the summer. Acute potassium starvation was observed. An autumn application of potassium chloride restored dry matter production to normal levels. Availability of soil K, expressed in terms of energies of replacement [ΔF(− 1)], decreased proportionally to the amount of nitrogen fertilizer applied. When ΔF reached approximately 4,250 cal/mol, overseeded legumes were K-deficient, whereas Rhodes grass at that value was still able to extinct sufficient K from the soil for normal growth.

Wheat (Triticum aestivum), mustard (Brassica juncea), gram (Cicer arietinum) and barley (Hordeum vulgare) seedlings were raised in soils of different tilth created in microplots during 1981 and 1982. Amplitude in diurnal seed-zone temperature and soil moisture content increased with tilth coarseness. At low soil moisture levels, seedling emergence of wheat and mustard decreased with increasing clod size while that of gram and barley increased. These effects were not significant at high soil moisture levels. Shoot growth of all the crops was higher under coarse tilth than under fine tilth at both moisture levels. Root growth of wheat and mustard decreased with increasing clod size while that of gram and barley increased, at both moisture levels. Mustard had the highest seedling emergence at the low moisture level. Seedling emergence and shoot growth were higher under high moisture than under low moisture for all crops. Root growth varied depending upon the type of crop.

The problems involved in the estimation of potential evaporation in the tropics are discussed, and available methods for calculating potential evaporation are assessed. A computer programme is described which evaluates Penman's formula, accommodating data from the very wide range of conditions experienced in tropical agriculture. The programme conforms with recent W.M.O. recommendations and is written for computers available in many parts of the world. An important component of the programme is a strict data validation procedure. The output includes daily and mean ten-day estimates of E, using the reflection coefficients for open water and for a crop as well as both calculated and, where available, measured values of radiation.

Low levels of phosphorus limit the yield of pearl millet (Pennisetum glaucum) grown on acid sandy soils of the West African Sahel. The application of phosphorus and the recycling of millet residues produces large increases in the total dry matter and grain yields of millet but little is known about the effects of these amendments on the by-products of millet fields which include weeds and millet leaves at harvest. Phosphorus applied at 13 kg ha−1 as single superphosphate and millet residues applied at 500 or 2000 kg ha−1 as a mulch or as the ash from 2000 kg millet residues ha−1 that had been burned, increased dry matter yields of millet leaves and weeds leading to large increments in the total in vitro metabolizable energy harvested per unit area. These increases in dry matter production were only accompanied by minor decreases in the concentration of crude protein. The increased availability of millet by-products should be taken into account when evaluating the effects of phosphorus and crop residue application on the economy and sustainability of agro-pastoral farming systems in the West African Sahel.

This paper uses survey results to show how one group of small scale farmers in Santa Cruz, Bolivia, were able to mechanize annual cropping despite a farming systems diagnosis which indicated that this was not a viable development path. It attempts to identify the underlying causes of farmer success and diagnosis failure.

The government of Thailand aims for sustainability of palm oil production in the Northeast for bioenergy and farmers’ income. This study investigated whether producers in Northeast Thailand managed their oil palm according to good agricultural practices (GAP) and if not, what effects this has on yield. A survey was conducted amongst 108 randomly selected farmers. For 25 selected plots, management and yields were monitored twice a month for two full years. Compliance to GAP was high for weeding, harvesting, pruning and pest and disease control but not for irrigation (40%) and fertiliser application (20–40%). GAP adoption scores per households positively correlated with income from other crops, tree age and degree of training. We showed that rainfall was insufficient for good oil palm growth between October and April. In the monitored group, use of irrigation and amounts of N, P, K and Mg applied were strongly correlated. The yield was significantly greater with irrigation and fertiliser, reaching similar levels as in the South of Thailand (up to 25–30 Mg Fresh Fruit Bunches: FFB ha−1), but did not differ with soil texture. This allows us to conclude that better application of GAP, especially including a combination of irrigation and fertilisers overcame the unsuitable soil and rainfall conditions in the Northeast of Thailand. However, the costs of fertilisers compared to the price of FFB affected the profitability of FFB production, which may affect farmers’ motivation to apply GAP, especially on unsuitable soils. When the government aims for sustainable palm oil production in the Northeast it needs to invest in frequent technical support, irrigation infrastructure and affordable fertilisers. Otherwise, farmers may not apply GAP because of low returns on investments and yields will remain very modest.

Our experience with potentially tropic-adapted grain legumes leads us to hypothesize that ‘with appropriate and sufficiently proven technology, developed specifically for the purpose, controlled environment facilities can be a powerful adjunct to field research and so assist in the attainment of crop improvement objectives in lentils’. This contribution comments on the ‘adaptation’ of grain legume crops to their environments, describes current lentil production in the USA and elsewhere, and discusses the tenets and objectives of a programme of research devoted to the ultimate release of lentil genotypes that are well adapted to the environments for which they are intended.

Regression analysis, stability variance method, and the genotype-grouping technique were used to investigate the relative yield stability of 20 soyabean genotypes, grown in 12 diverse environments in Malaysia in 1978. With the regression analysis, four genotypes were observed to be unstable for grain yield; however, for the remaining 16 genotypes with non-significant regression coefficients, a substantial proportion of the g × e interaction was non-linearly related to the environmental indices. With the second and third methods less than half of the genotypes turned out to be stable for grain yield. Generally, for some genotypes, the stability classification was the same for all three methods.

Three cultivars of mustard (B. juncea) were grown on field plots with five levels of fertilizers and with or without irrigation. Irrigation gave 59% more seed yield than no irrigation, accompanied by improved performance of ancillary characters. Significant increases in seed yield and most of the other characters were noted with increased levels of fertilizers, with a significant cultivar × fertilizer interaction due to the negative response of one cultivar to increased levels of fertilizers. The importance of irrigation and fertilizer in mustard seed production was thus demonstrated.

Four cultivars of cowpeas (Vigna unguiculata L. Walp.) were grown in 15 sets of conditions (environments) i.e. in several monthly plantings in each of three years. Data for seed yield were analysed to investigate the effectiveness of using planting dates in preliminary yield trials of new cultivars. Extremely significant environment mean squares and wide ranges of environmental indices (− 13.3 to 23.5) and seed yield (11.4 to 48.2 g plant−1) indicated real differences among environments. Stability analyses of the cultivar × environment interactions suggest that, where limited funds preclude the use of several locations, monthly plantings for two or more years could be used effectively in the preliminary evaluation of cultivars without losing much information on their relative ranking.

Maturation of peas in cool temperatures (mean 17.5°C) at Dalang Maidan, Lahaul (in the Himalayas) led to the development of larger seeds in comparison to those of the same varieties which had matured in warmer temperatures (mean 24.5°C) at Delhi, India. The larger seeds from Lahaul, when sown at Delhi, gave rise to taller plants which came into flower earlier compared with those from the seeds matured at Delhi. Significant location ′ variety interactions were recorded for germination and plant height. Inherent variation in days to flowering could have been a major factor in these interactions. These data are of direct importance to breeders using seeds developed at more than a single location if environmental conditions differ appreciably.

Rice is the staple crop of Guinea Bissau, and its production system is based on human labor with very limited possibility of mechanization, particularly in the Mangrove ecosystem. Due to this and to the low possibilities of controlling environment parameters, such as water level and availability, the genetic resistance to extreme abiotic factors was identified as a key point for increasing yields quantity and stability. Among the ample genetic material available in the country, no purification activities were carried out in the past decades. This led to the cultivation of mixtures or ecotypes and not to uniform varieties, with consequent issue related to cultivation and milling. On 103 samples collected, only on about 50% of ecotypes, the purification was carried out as the remaining half was too much variable. The purification ended with less than 20% of material considered stable and uniform varieties. Moreover, the program adopted a bottom-up approach for collection and variety conservation to drive the program and improve the genetic material.

A grazing management study involving the new white clover cultivar Osceola grown in association with Bahiagrass cv. Pensacola was conducted on wet and dry sites with and without pesticide/herbicide treatment. A combination of heavy grazing pressure and a short deferment period before grazing during the summer and autumn resulted in the largest soil seed reserves and seedling recruitment by the white clover component. However, maximum survival of plants was recorded from a combination of a short deferment period and moderate grazing pressure.

A slight increase in plant survival and seedling recruitment was shown on the wet site. Survival potential was least in pasture treated with pesticide and herbicide. Heavy grazing pressure and short deferment periods appear essential for the survival of the clover component. Annual seedling recruitment from soil seed reserves was the primary mechanism of white clover survival from spring to spring in pasture associations based on tropical bahiagrass.

The environmental conditions and test duration in rainfall simulators have been major constraints to find reliable differences in preharvest sprouting (PHS) among wheat cultivars. This study aimed to elucidate the temperature conditions and degree-days (DD) that enable higher discrimination of genotypes in a PHS test. Thirteen genotypes with different degrees of PHS (BR 18, BRS 220, CD 104, CD 105, CD 108, CD 114, CD 116, Frontana, IPR 085, IPR 128, IPR 136, OR1 and Safira) were evaluated in a rainfall simulator, during four years, conducting two trials per year. The tests were carried on 20 spikes per cultivar, kept in a vertical position on Styrofoam plates, spaced 10 cm between rows and 5 cm within the row. The air temperature data were recorded on a thermograph and the DD were calculated from the mean daily air temperature assuming a base temperature of 4 °C. The Falling Number (FN) parameter and germination percentage (GP) data were averaged for each test. The temperatures (minimum, mean and maximum) and the DD were regressed and correlated with FN and GP. Any increase in the minimum and mean air temperature and accumulated DD decreased FN values and increased GP. Higher genotypic discrimination was achieved at an average air temperature of 21.5 °C and 35 DD. These values can be used as reference to set simulated rain testing condition for screening genotype for PHS based on FN or pericarp rupture of grains.

A random sample of 13 uniformity trials was examined in terms of sensitivity to choice of block size and orientation. Five trials were classified as insensitive and eight as sensitive. Trials insensitive to blocking choices showed little variation in experimental error for various sizes, shapes and orientations of blocks, but those sensitive to blocking choices showed considerable, sometimes drastic, effects of such choices. There was often an objectionable degree of inflation of experimental error due to large or improperly oriented blocks. It is proposed that the routine analysis of field experiments based on block designs be modified to reveal cases in which ineffective blocks have been used on sensitive sites.