Optimum plant population for maize-bean intercropping system in the Brazilian semi-arid region.

The main objective of the study was to investigatethe effect of different plant populations of maize and beans, at two nitrogen levels, on the performanceof the component crops

Effects of plant population and nitrogen fertilizer on yield and efficiency of maize-bean intercropping.

Nitrogen supply and plant population are basic parameters for cereal-legume intercropping. In order to study plant population and nitrogen fertilizer effects on yield and yield efficiency of maizebean intercropping, a field experiment was established. Three bean plant populations and three nitrogen levels were used. Maize dry matter accumulation decreased with increases in bean plant population. Competitive effect of intercrop beans on maize yields was high at higher plant populations, being decreased by nitrogen fertilizer; application of 50 kg ha-1 N was very efficient in increasing maize cob yield. Intercropping significantly decreased harvest index of beans in all plant population and nitrogen fertilizer situations. The efficiency of intercropping, compared to sole cropping, was evidenced by the values obtained for Land Equivalent Ratio (LER) for biomass, cob and pod yields that increased with increases in bean plant populations and nitrogen fertilizer levels

Evaluation and Presentation of Intercropping Advantages

It is proposed that two distinct objectives should be recognized in the evaluation of intercropping advantages: (i) a biological objective to determine the increased biological efficiency of intercropping and (ii) a practical objective to determine the advantages that are likely to be obtained by a farmer. The sole crop systems with which intercropping must be compared to satisfy these objectives are defined. Evaluation in relative, absolute, monetary and nutritional units is discussed and some aspects of presenting intercropping data in graphical form are illustrate

Genotypic variation in the response of sorghum to intercropping with cowpea, and in the effect on the associated legume.

Selection of sorghum genotypes for the sorghum-cowpea intercrop system would be simplified if it could be done in sole crop. In order to compare evaluation in sole crop and in the presence of the standard cowpea cultivar c 152, sorghum inbred lines, F2 hybrids and land races which differed in maturity date, height and canopy characters were grown in the two systems in two seasons at Hyderabad,India. Cowpea sole crop was included as an additional treatment. Sorghum canopy characters and yield components in intercrop were highly correlated with the same characters in sole crop. How-ever, multiple regression of sorghum grain yield in intercrop on characters measured in sole crop. Characters related to light interception were the most influential in determining sorghum yield, but some genetically determined variation in yield was unexplained by either multiple regression. Characters related to light interception had a negative influence on cowpea yield, though again some variation due to sorghum genotype was unexplained. Thus although the influence of sorghum plant characters on each component crop is predictable, compensation between the components makes the overall outcome more difficult to predict, and dependent upon which component isfavoured by the environment. The sorghum genotypes selected will therefore represent a compromise: they should not be dwarf types, but should be early maturing to escape drought, and have narrow canopies so as not to be too competitive on the cowpea. The final selection should be made in intercrop

Genotype studies at ICRISAT

Genotype experiments carried out at ICRISAT Centre 1976-8 are decribed. A sorghum/pigeon pea experiment in 1977 examined 17 genotypes of pigeon pea with a standard sorghum genotype. Sorghum produced yields ranging from 82 to 99% of the sole-crop yield, but the differences were not significant. The pigeon pea genotypes achieved yields ranging from 36 to 73% of their sole-crop yields, giving total land equivalent ratios (LERs) up to 1.66. Although absolute pigeon pea yields in intercropping were dependent to some extent on sole-crop yields, this dependency only accounted for 40% of the variability in intercrop yields. There were indications that the most suitable pigeon pea plant type had a reasonably compact growth in the early stages to avoid competition from the sorghum but a spreading habit later to utilize resources after sorghum harvest. In 2 experiments, 3 pearl millet genotypes were examined in all combinations with 4 groundnut genotypes. Yield advantages up to 25-30% were achieved. It was concluded that the magnitude of the yield advantage was mainly determined by the groundnut genotype, whereas the proportion of groundnut yield to millet yield was mainly determined by the millet genotype. 3 sorghum/millet genotype experiments are described. In the 1st experiment 48 genotypes of pearl millet were grown with a standard sorghum genotype. Correlations between yield advantage and a range of millet plant characters did little to help identify which characters were most desirable in intercropping. The 2 later experiments examined 4 sorghum genotypes in combination with 4 millet genotypes. Yield advantages ranged up to just over 30%. These were considered to be very large advantages for 2 such similar crops; this combination is particularly worthy of further stud

Stability of performance of a pigeonpea/sorghum intercrop system

Results of 89 experiments available on sorghum (Sorghum bicolor)/pigeon pea (Cajanus cajan) intercrops have been pooled, and some basis for understanding the stability of performance is presented. On the average, the intercrop system provides the equivalent of 90% of the sole sorghum yield and about 52% of the sole pigeon pea yield. The relative advantage of intercropping remained more or less similar at different levels of fertility. There was no relationship between relative advantage and the amount of water used. Regression analysis showed that the intercrop system is superior to sole crops at all levels of yields and is more widely adaptabl

Preliminary studies of intercropping combinations based on pigeonpea or sorghum

Various intercrops were examined in an alternate row pattern with pigeonpea or sorghum on both Alfisol (red soil) and Vertisol (black soil). The slow-establishing and later-maturing pigeonpea combined well with earlier cereals and legumes to give very large yield advantages as measured by the Land Equivalent Ratio. In the pigeonpea/cereal combinations, the earlier the cereal the bigger the yield advantage tended to be, attributed to improved use of resources over time as the difference in maturity periods of the component crops increased. Sorghum was generally more competitive than pigeonpea and intercropping advantages tended to be less. But even where there was little difference in maturity periods of the component crops, both sorghum/legume and sorghum/cereal combinations gave substantial and statistically significant advantages, suggesting that improved ‘spatial’ use of resources was also importan

Effect of row arrangement on light interception and yield in sorghum-pigeonpea intercropping

Two experiments examined the effect of improving the distribution of the pigeonpea plants in sorghum-pigeonpea intercropping by having an alternate row arrangement of the two orops (SP) instead of the two sorghum: 1 pigeonpea row arrangement (SSP) that was studied earlier. One experiment was under conditions of good moisture supply (a deep Vertisol site in the high rainfall year of 1978) but the other experienced early moisture stress and had much lower end-of-season soil moisture storage (an Alfisol site in 1979). In 1978 the proportional sorghum yield was not affected by row arrangement (86 and 85% of the sole crop yield for the SSP and SP treatments respectively). Under the drier Alfisol conditions of 1979, the proportional sorghum yield was lower, probably because of the increased competitive ability of the drought resistant pigeonpea, and it was adversely affected by the alternate row arrangement (72% for SSP and 60% for SP)

A Competitive ratio for quantifying competition between intercrops

A simple competitive ratio (CR) is proposed as a measure of intercrop competition, to indicate the number of times by which one component crop is more competitive than the other. Intercropping data show that this CR term could be useful in (i) comparing the competitive ability of different crops, (ii) measuring competitive changes within a given combination, (iii) identifying which plant characters are associated with competitive ability, and (iv) determining what competitive balance between components is most likely to give maximum yield advantage

Evaluation of yield stability in intercropping: Studies on sorghum/pigeonpea

Data from 94 experiments on sorghum/pigeonpea intercropping were examined for evidence that the stability of yield is greater with intercropping than sole cropping. Stability of the major component (sorghum) was examined by calculating the distribution of yields; stability of the overall intercropping system was examined by calculating coefficients of variation, by computing regressions of yield against an environmental index, and by estimating the probability of monetary returns falling below given ‘disaster’ levels. All these approaches have some merit; taking the last as an example, it was found that for a particular ‘disaster’ level quoted, sole pigeonpea would fail one year in five, sole sorghum one year in eight, but intercropping only one year in thirty-six. Intercropping gave yield advantages under a wide range of environmental conditions and there was no significant evidence that advantages were greater under stress. This is discussed in relation to possible mechanisms contributing to greater yield stabilit