Productivity and Seed Quality of Corn and Mung Bean in Relation to Pest Management, Fertilizer Sources, and Cropping Patterns

The study was conducted to compare growth and seed production performance of corn (variety Nakhon sawan 1) and mung bean (variety Kampangsan 2) when monocropped or intercropped, and under various pest management system (no pest control, applied with botanicals or chemical pesticide) and fertilization regime (no fertilizer, organic fertilizer, and inorganic fertilizer) for two seasons (wet and dry) at the Nakornsrithammarat Campus, Nakornsrithammarat, Thailand. The fertilizers used were poultry manure (78.8 - 49.1 - 52.1 and 25.0 - 15.6 - 16.5 kg N-P-K ha-1 for corn and mung bean, respectively) and inorganic fertilizer (78.8 - 62.5 - 0 kg N-P-K ha-1 for corn and 25.0-3 1.3 -0 kg NP- K ha-1for mung bean). The botanical treatment was comprised of neem powder (50 kg ha^-1), garlic solution (9.0 g garlic/I, applied at 250 I ha^-1), and lemon grass and marigold grown around the experimental plots. The chemical pesticides used were based on Thailand's official recommendation for corn and mung bean production (DAE, 1993 a,b). All mung bean plots were inoculated with Rhizobium. Tillage was done during the first cropping (wet season only). The treatments were combined in a 3 x 3 x 2 factorial, arranged in a split-split plot in randomized complete block design (RCBD) with three replications. The pest management, fertilizer source, and cropping pattern served as mainplot, subplot and subsubplot, respectively. Parameters measured at different stages of growth were plant height (cm), leaf area index (LAI), total dry matter yield (g m-2and g plant-1), crop growth rate (CGR, g^-2 , d^-1 plant^-1), incidence of pest and plant disease, and nodule dry weight (g m-2 for mung bean), weed dry weight (g m-2 for corn only), seed yield (t ha-1 and g plant^-1) and yield components, harvest index (HI), land equivalent ratio (LER), area time equivalent ratio (ATER), seed quality [laboratory germination (percent), field emergence (percent), germination accelerated aging (percent), seedling length (cm) and seedling dry weight (g)], nutrient (NPK) concentration (percent) and content (g m^-2 in various plant parts, soil parameters such as soil pH, extractable cations (ppm), organic matter (percent), soil nutrient concentration [N (percent), P (ppm), K (ppm), Ca (ppm), Mg (ppm), and Na (ppm)] and earthworm dry weight (g m^-2) . The economics of crop and seed production of the different treatments was also assessed.

The agronomic and seed production performances of corn and mung bean were better during the wet season (first cropping) than during the dry season (second cropping). In both seasons, occasional significant two-factor and three-factor interactions occurred but no significant patterns could be identified. Pest and disease incidence was generally low in both seasons.

For corn, different pest management did not affect growth, seed, and soil parameters in both cropping seasons except in earthworm population where chemical pesticides in both seasons was much lower half than other pest management treatments. Different fertilizer sources also generally did not have an effect during the wet season. During the dry season, however, differences in most parameters were found, mainly due to the positive influence of poultry manure. The effect of no fertilizer and inorganic fertilizer treatments were generally similar. Corn fertilized with poultry manure had 4 times growth parameters, 29 times seed yield, and 1 time higher seed quality than the other fertilizer treatments. Poultry manure may have influenced soil structure and nutrient availability though this was not reflected in nutrient concentration in plant tissues or soil. Other soil parameters such as pH, soil organic matter (soil N), P, K, Ca, Mg. and Na did not change over seasons. Most notable was the earthworm population which was highest in plots applied with poultry manure.

Intercropped corn gave higher values than the monocrop tor growth parameters such as LAI , total dry matter yield. CGR, seed yield, LER, and nutrient content tor both seasons. However, these were partly due to greater population density of the former. No significant difference between monocrop and intercrop was generally found in these and other parameters determined on per plant basis. On the other hand, cropping patterns did not influence mung bean growth parameters in both seasons. For seed yield (per plant or area basis) and HI, however, the monocrop was higher than the intercrop by nine percent. Soil nutrients were also not affected by cropping patterns except organic matter (soil N), which was higher in intercrop than in the corn and mung bean monocrop. This may be due to N-fixation by mung bean as reflected in greater nodules for intercrop.

Response of mung bean to pest management and fertilizer sources was similar to corn in both seasons. However. mung bean applied with chemical pesticide was more infected than those given other treatments at 4-6 WAE. Unlike corn, however. mung bean differed in seed yield with fertilizer sources during both seasons. During the wet season, poultry manure gave 5 and 16 times higher in seed yield than inorganic fertilizer and no fertilizer treatments, respectively. Growth during the dry season was also better with poultry manure than with other fertilizer treatments. Inorganic fertiIizer suppressed nodulation at any stage of growth during the wet season but not in the dry season. Earthworm population, as in corn, was also negatively affected by inorganic fertilizer and chemical pesticides in both seasons. Soil property nutrients, as in corn, were not affected with pest management, fertilizer sources, and cropping patterns in both seasons except by fertilizer source during the dry season for corn. Poultry manure enhanced corn seed germination percentage (approximately by 30-90%), storability (approximately by 50-100%), field emergence (approximately by 25-60%), seedling dry weight (approximately 125%), and seed ling length (approximately by 50-90%) during the dry season.

A cost and return analysis in the first corn and mung bean cropping where reasonable yields for all treatments were obtained indicated higher net returns per unit area from the no pesticide, combined with poultry manure treatment. The net returns from corn when intercropped with mung bean was lower than the corn monocrop but higher than mung bean monocropping system. It is suggested, however, that the analysis should factor in externalities incurred such as chemical inputs and allow adjustments in values because of extrapolation from relatively small plots.

Results indicated that nonchemical pesticide management, fertilization using poultry manure, and intercropping systems can be as viable as the conventional system (chemical pest control, inorganic fertilizer application, and monocropping) for corn and mung bean crops and seed production. Benefits can already be realized in the first season, but differences among treatments were more apparent during the second cropping. Since crop response may have been compounded by the effect of season (i .e., rainfall and, consequently, soil conditions) further tests that include larger plot sizes, extended time periods, and other agroecological conditions would be useful.