Cropping systems research to improve the productivity of an acid upland rice and maize-based farming system is described and evaluations by co-operating farmers are presented. Farmers rejected introduced patterns. The cropping choices of non-cooperating farmers are described in terms of cost–benefits and the reasons underlying their decisions. An approach that combines an understanding of farmers' systems in order to conduct focused research on the weak points of such systems, together with an evaluation of farmer technology and adaptation, may be more effective than researcher-designed, farmer-implemented cropping pattern trials.

Red pea (Lathyrus cicera L.) is an underutilized protein crop with broad adaptability. Intercrops of red pea with winter cereals have not been studied. A two years field study was conducted with the objective to determine the productivity of intercropping systems of red pea with barley (Hordeum vulgare L.) and triticale (xTriticosecale Wittmack) in two seeding ratios (60:40 and 80:20). Growth rate, dry matter yield, protein content and yield were determined. Several indices were used to evaluate the intercropping systems and analyse competition and interrelationships between mixture components. Growth rate of cereals was lower in the mixtures than in the monocrops. Dry matter yield were the highest in barley monocrop and its intercrop with red pea at 60:40 seeding ratio. Red pea monocrop showed the highest crude protein concentration followed by its intercrops. The land equivalent ratio, relative crowding coefficient (K), actual yield loss (AYL) and system productivity index values were greater for the red pea-barley 60:40 mixture, indicating an advantage of intercropping. The partial K, aggressivity, competitive ratio and partial AYL values indicated red pea as the dominated species in the intercrops. The highest monetary advantage value was recorded for the red pea-barley mixture (60:40). The results indicate that red pea-barley mixture (60:40) was the most productive and produced better forage quality and thus could be adopted by the farmers as alternative option for forage production.

The yield and gross returns (Rs/ha) were studied over two years in three experiments on intercropping in corn and sorghum. Paired-row planting recorded 8 to 12% and 44% higher yield in corn and sorghum respectively over conventional equidistant planting at the same plant populations. Additional gross returns due to intercropping ranged from 24 to 76% in corn (1975–76 winter) and 4 to 56% in corn and 15 to 75% in sorghum (1976 rainy season) compared to pure crops. Intercropping was beneficial, particularly in the limited cropping periods of this semi-arid tropical zone.

Response to potassium fertilization was tested, over a two-year period, in 24 experimental fields, predominantly in coarse-textured soils. Only two fields showed significant yield increases. Potassium availability was estimated on the basis of (a) the free energy (ΔF) of potassium exchange for calcium and magnesium, (b) the proportion of potassium in total exchangeable cations, and (c) soluble potassium extraction in correlation with the potassium content of the plants. Woodruff's method (ΔF) yielded the best agreement (correlation coefficient r = 0·77). ΔF values showed a sufficient supply of available potassium, which may have accounted for the lack of response to fertilization.

Best management practices in agriculture have the potential to sequester carbon and improve soil aggregation. Hence, in the present investigation, different levels of irrigation and nitrogen (inorganic and organic) were used in the maize–wheat cropping system to study their effect on soil organic carbon (SOC) accumulation and aggregation. The treatments consisted of three levels of water regimes (namely W1, W2 and W3 referring to limited, medium and maximum irrigation) and five nitrogen levels (T1, 0% N; T2, 75% N; T3, 100% N; T4, 150% N; T5, 100% N from organic source), with three replications taken in a split plot design. Positive and significant correlation between SOC and mean weight diameter (MWD) was observed, implying that increasing SOC improved soil structure and increased the MWD. The quantification of water and nitrogen interaction on SOC was done by developing a multiple regression equation, which, when validated with SOC of the subsequent year, resulted in significant correlation. Irrigation and N was found to have a significant effect on soil aggregation and organic carbon build-up. Two N treatments (T4: 150% N and T5: 100% N from organic source) improved soil aggregation (macro-aggregates) and SOC when accompanied with W3 water regime (maximum amount of irrigation). Across N treatments, the W3 regime registered significantly higher SOC by more than 30% over control in the 0–15-cm soil depth.

Experiments in Brazil have shown that a sorghum-pulse (cowpea or common bean) intercrop system yielded more grain than the monocrop system and produced a Land Equivalent Ratio (LER) greater than 1.00 even though rainfall was limited. Sorghum competed less than maize with the associated pulse when Competitive Ratios (CR) were considered. In cowpeas, CR values were correlated positively with the number of pods and seeds plant−1. The two crops in the intercrop systems were responsive to fertilizer application. Thus, improved management (i.e. fertilizer usage) was appropriate without the loss of the advantageous effects realized from intercropping.

Using computer simulation model as a management tool requires model calibration and validation against field data. A three-year (2008–2009 to 2010–2011) field study was conducted at the Postgraduate Agricultural Research Station of the University of Agriculture, Faisalabad, Pakistan, to simulate wheat grain yield production as a function of urea fertilizer applications using Crop Environment REsource Synthesis (CERES)-Wheat model. The model was calibrated using yield data for treatment of urea fertilizer application at the rate of 247 kg-urea ha−1 during growing season 2009–2010 and was validated against independent data sets of yield of two years (2008–2009 and 2010–2011) for a wide variety of treatments ranging from no urea application to 247 kg-urea ha−1 application. The model simulations were found to be acceptable for calibration as well as validation period, as the model evaluation indicators showed a mean difference of 8.9%, ranging from 0.05 to 15.38%, root mean square error of 356 having its range from 242 to 471 kg ha−1, against all observed grain yield data. The scenario simulations showed maximum grain yield of 4100 kg ha−1 for 350 kg-urea ha−1 in 2008–2009; 4600 kg ha−1 for 300 kg-urea ha−1 in 2009–2010 and 5200 kg ha−1 for 340 kg-urea ha−1 in 2010–2011. Any further increase in urea application resulted in decline of grain yield function. These results show that model has the ability to simulate effects of urea fertilizer applications on wheat yield; however, the simulated maximum grain yield data need field-based verification.

Smallholder livestock systems in Central America are typically based on pastures with traditional grasses and associated management practices, such as pasture burning and extensive grazing. With the rise of the global population and a corresponding increase in demand for meat and milk production, research efforts have focused on the development of improved grasses and the incorporation of legume species that can increase productivity and sustainability of Central American livestock systems. However, farmer adoption remains very limited, in part due to the lack of site-specific evaluation and recommendations by local institutions. Using a multi-site participatory approach, this study examined the potential of five improved grasses and five species of forage legumes as alternatives to the broadly disseminated grass Hyparrhenia rufa (cv. Jaragua) in pasture-based cattle systems in western Honduras and northern El Salvador. Improved grasses (four Brachiaria sp. and Megathyrsus maximus) produced significantly more biomass than H. rufa; also four of the five legume varieties evaluated (Canavalia ensiformis, Canavalia brasiliensis, Vigna unguiculata, and Vigna radiata) demonstrated high adaptability to diverse environmental conditions across sites. Farmer participatory evaluation offers a valuable means to assess performance of forages and will likely contribute to their improved utilization. Future research is needed on more refined management recommendations, pasture system design, costs and environmental benefits associated with the adoption of these forages in local livestock production systems.

Maize (Zea mays L.) grain yield is severely constrained by drought and this study was conducted to assess gains in grain yield and other traits of released maize cultivars. Twenty-three maize cultivars plus a check were evaluated under drought and well-watered conditions at Zaria and Kadawa during 2015/2016 and 2016/2017 dry seasons. The 24 cultivars were evaluated using 6 x 4 lattice design with three replications. Genotypes differed significantly for all measured traits except anthesis-silking interval (ASI), husk cover, and number of ears per plant under drought, and ASI, husk cover, and ear aspect under well-watered conditions. Under drought, grain yield ranged from 2251 kg ha−1 for SAMMAZ 31 to 4938 kg ha−1 for SAMMAZ 19, with a genetic gain of 1.93% yr−1. Under well-watered conditions, grain yield varied from 3082 kg ha−1 for SAMMAZ 37 to 5689 kg ha−1 for SAMMAZ 51, with the same genetic gain found under drought conditions. Grain yield reduction as a result of drought was 28.4% and performance under drought predicted performance under well-watered conditions better than vice versa with regression coefficient value of 0.8. Grain yield had significant correlations with all measured traits under both water conditions, except for husk cover, plant and ear heights under drought. Our data revealed that substantial genetic gains have been made in breeding for high grain yield cultivars under drought and well-watered conditions over a period of 16 years in Nigeria.

Using a qualitative case study design, a demonstration farm approach implemented in northern Patagonia, Argentina, was assessed to examine differences in perceptions between participating stakeholder groups regarding their roles and how these affect the collaboration process. Moreover, differences in stakeholder perceptions regarding positive impacts and constraints of the implemented innovation (supplemental feeding of small ruminants) were assessed, as one exemplary innovation to improve low-external-input pastoral livestock systems. Three cases of demonstration farm projects were selected and a total of 31 semi-structured and narrative interviews were carried out with participating livestock keepers, extension workers and scientists. Together with information gained by employing visual tools and participant observation, data was analysed using qualitative content analysis. Results reveal that major decisions regarding the collaboration process were taken by scientists in advance, hence, livestock keepers' participation was used to meet predetermined objectives, which is characteristic to the concept of functional participation. While scientists seemed to transfer the control principles of on-station research to the on-farm situation, extension workers recognised the need for replacing teaching by the aim of creating learning opportunities. Here, incongruences in role understanding indicate an overall lack of joint role definition and the need of balancing power differences. Livestock keepers' perceptions of the supplemental feeding strategy highlight substantial management constraints for implementation, which were not recognised by scientists and extension workers, nor were they captured by the monitoring system implemented. We recommend furnishing the demonstration farm approach with principles, methods and tools of collaborative learning, to create a change in actors' understanding of roles and to induce a shift towards increased transdisciplinarity.

The effects of nitrogen fertilization on growth, nutrient uptake and yields of upland and lowland taro were studied on the island of Kauai, applying o, 280, 560 and 1120 kg./ha. N. Nitrogen concentrations of upland and lowland taro leaves were significantly correlated with yields, although regression analysis showed that per cent N in both blades and petioles decreased with age. Higher yields were obtained from the lowland than from the upland crop, regardless of amounts of N fertilizer applied. The highest yield obtained from lowland taro was at 1120 kg./ha. N harvested at fifteen months (57·6 tons/ha.) and from upland taro the highest yield was obtained at 560 kg./ha. N harvested also at fifteen months (25·5 tons/ha.).

The effect of seven planting densities on yield and witches' broom disease incidence in hybrid cacao (Theobroma cacao) trees in the Brazilian Amazon was investigated. Data collected over a three-year period showed that it was possible to optimize regional cacao yield by high planting densities (2500 and 1666 trees ha−1) and that there was no density × year interaction. However, high planting density also favoured witches' broom incidence. A growing regional interest in planting cacao clones at high planting density should be pursued with caution, since high planting densities of clones in environments under strong pressure of selection for the witches' broom pathogen, such as in the Amazon region, are still a risky strategy. Alternatives to the high planting density system are presented and discussed.

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.

Under rainfed conditions in Tarlac, Central Luzon, Philippines, risk was characterized using field and household panel data for 46 rice farmers over the period 1990–93. Measures of risk at the field level were calculated using pooled time-series cross-sectional data. Field-level risk was found to be quite high, with the average coefficient of variation of yield being 45% and 30% for fields with low and moderate elevations respectively. Farmers applied less nitrogen in fields with higher yield variability, and adjusted the quantity of nitrogen in order to reduce losses in poor years and benefit from greater potential in good years. Farmers with higher levels of education had lower variability of rice income than farmers with a lower level of education. Non-crop income helped reduce total income variability, especially for farmers with high variability of crop income. Implications for technology design and policy improvements are derived from these results.

In 1981 and 1982, three crop protection regimes were compared with an unsprayed control for cowpea grown alone and in mixtures with maize, sorghum and cotton. Unsprayed cowpea in mixtures with maize had yields which suggested some pest escape in 1981 but not in 1982. When sprayed, only the maize–cowpea mixture showed much yield advantage over sole crops. For maize–cowpea in 1983, a very dry year, only the alternate row mixtures showed a yield advantage and three spray applications gave cowpea yields as good as those resulting from six applications. The late, photosensitive cowpea variety Acq 1696 had better yields than the medium maturity TVx1948·01 F in the mixed crop but was greatly inferior as a sole crop.

Judicious management of our natural resources is a major pillar of sustainable agriculture, broadly defined. It is, therefore, unfortunate that, until now, research in natural resources management (NRM) has not received sufficient support, or the recognition that other agricultural research topics have had. The Consultative Group on International Agricultural Research (CGIAR) recognized, early on, the complementarities and synergies between NRM research and other themes, notably genetic improvement, and its research Centres have pursued some vigorous programmes for many years. The Technical Advisory Committee (TAC) to the CGIAR was supportive of such programmes from the start and provided advice to the CGIAR System on NRM research strategies. Highlights of such advice over the last 20 years are discussed, including the ecoregional approach, the 1996 study of Priorities and Strategies for Soil and Water Research, and the CGIAR Vision and Strategy of 2000. Recent developments at the Centres leading to the promotion of integrated approaches to NRM (INRM) are described, and a set of priority areas in INRM research for future CGIAR activities is presented.

The impact of liquid cattle (Bos taurus L.) manure, applied to soil at common rates and for several years, on certain plant parameters and soil properties has not been studied extensively. The objectives of this study were: a) to assess the effects of manure application on corn (Zea mays L.) yield, macro- and micronutrient concentrations and uptake, in a three-year (2006–2008) field experiment conducted in northern Greece and b) to evaluate the 11-year effect of manure application on soil fertility (particularly on micronutrients avialability) and chemical properties (especially on organic C and total N content). The field experiment of this study had been used in a similar fertilisation experiment since 1996. The treatments, which were applied on the same plots each year over the 11-year period, were: (i) soil incorporation of liquid dairy cattle manure before sowing, at a rate equal to the common N-P inorganic fertilisation for each crop (based on manure's total N and P content); (ii) application of the common inorganic N-P fertilisation for each crop before sowing; (iii) identical to ii, but with split application of the N fertilisers; (iv) no fertilisation (control). Corn dry aboveground biomass yield at the R3 growth stage and grain yield, N, P, K concentrations and macro- and micronutrients uptake increased (p ≤ 0.05) upon manure addition at levels similar to or higher than the inorganic fertilisation treatments. The relative increase in grain yield during the three-year period ranged between 63–75% for manure treatment and 50–75% for both inorganic fertilisation treatments. After 11 years of manure application, organic C, total N, and available NO3-N, P, K, Cu, Zn, Mn, and B increased (p ≤ 0.05) in the surface soil (0–30 cm). However, no trend of nutrient build up was evident through years (except for Zn). Surprisingly, salinity and available NO3-N in the 60–90 cm soil depth of the manure-treated plots were lower (p ≤ 0.05) than that of the inorganic fertilisation treatments and similar to control. Electrical conductivity was 1.76, 3.05, 2.96 and 1.36 dS m−1, for manure treatment, the two inorganic fertilisation treatments and control, respectively, whereas the respective NO3-N concentrations were 7.7, 44.6, 55.1 and 8.3 mg kg−1. Conclusively, repeated application of liquid cattle manure into the soil, at rates comparable to the common inorganic fertilisation for 11 years, can enhance crop yield and macronutrient concentrations in plant tissues and uptake, at levels similar to the inorganic fertilisation. In addition, it can increase micronutrients plant uptake and maintain soil fertility with respect to both macro- and micronutrients and increase soil organic C and total N, without either causing nutrient build up or increasing soil salinity and NO3− accumulation in the deeper soil layers.

The nature of the soil, the influence of previous natural grassland, ley, fallow or cultivation, and the weather conditions before and after planting are shown to affect the yield of wheat, and its response to fertilizers, especially nitrogen. Out of seventeen experiments over four seasons, involving nitrogen top-dressings on wheat, thirteen gave economic increases after the application of I cwt per acre of ammonium sulphate nitrate (A.S.N.). Such applications to the first, second or third wheat crops after Rhodes grass (Chloris gayana) ley, or to land continuously cropped for a number of years, nearly always gave an economic increase in grain yield, but on continuously cultivated land, with normal rainfall after planting, an economic return to a second cwt per acre was probable. Following a one-season fallow, economic responses to nitrogen only occurred when the pre-planting period was very wet. Yields of wheat after ley, both with and without applied nitrogen, tended to be superior to those on continuously-cropped land. Responses to phosphorus only occurred in one area, where the importance of applying both N and P, particularly to newly-ploughed grassland, was very evident. Loss of organic matter, and structural deterioration accompanied by lower efficiency in the utilization of water and nitrogen, are probably the main causes of falling yields on soils cultivated for many years. The use of grass/legume leys is suggested as the best means of maintaining these naturally fertile soils in a highly productive state, even though the present returns from the legs themselves may be less profitable than wheat cropping.

Topdressing of N fertilizer, whenever leaf greenness, as measured by Chlorophyllmeter (SPAD), falls below the threshold value can be used for site-specific N management in wheat cultivation. Herein, a field experiment was conducted to analyse the effect of SPAD-based N management on wheat productivity and N use efficiency during the dry season of 2010/11 and 2011/12 on acid lateritic soil of eastern India. The experiment had 12 treatments, with nine treatments combining three SPAD thresholds (38, 40 and 42) and three N levels (15, 25 and 35 kg N ha−1) as real time N management (RTNM), one fixed time N management (FTNM), one farmers’ fertilizer practise (FFP) and control (Zero N), with three replications. The grain yield of RTNM ranged from 90 to 113% as that of FTNM, but using considerably less N. Maintaining SPAD threshold of 40 up to heading stage by topdressing 25 kg N ha−1 at each time (N25S40) caused the highest grain yield (4483 kg ha−1). While saving 22.5 kg N ha−1 (18.8%), N25S40 increased agronomic N use efficiency by 58.5%, nitrogen recovery efficiency by 15.1% and partial factor productivity of applied N by 26.4% when compared with conventional fertilizer recommendations (i.e. FTNM). The SPAD-based N management strategy was found very promising in efficiently managing N fertilizer in wheat for improving wheat productivity and N use efficiency.

Topsoil depth and yields of sorghum, pearl millet and castor bean were found to be positively correlated when monitored over thirteen seasons under widely varying rainfall conditions on an Alfisol in Andhra Pradesh, India. Yields responded up to 2.5 times more to topsoil depth when rainfall in the critical period exceeded evapotranspiration than under drier conditions. Yield variations were explained by topsoil depth in cereals, and by the interaction between rainfall during the critical period and topsoil depth in cereals and castor bean (R2<0.72). The expected yield losses as a result of erosion, based on 56 years of rainfall data, were 138, 84 and 51 kg ha−1 cm−1 for sorghum, pearl millet and castor bean, respectively. Quadratic models explained the yield losses due to cumulative erosion under conditions of both poor and good rainfall during the critical period. Sorghum and pearl millet tended to produce no yield when erosion exceeded 34 cm and castor bean when it exceeded 40 cm. There was less reduction in yield when rainfall was poor, up to about 10 cm of erosion, than when rainfall was good. The results indicate that pearl millet and castor bean are more suitable than sorghum for low rainfall and eroded conditions.