Different nutritional deficiencies or toxicities may limit bean development and yield. N and P deficiencies are the most frequent, although deficiency of minor elements and Al/Mn toxicity can reduce yields considerably. Nutritional problems are usually diagnosed by soil and plant tissue analyses and the observation of symptoms produced by nutritional disorders. Optimum pH for bean production varies between 6.5-7.5; within these limits, the majority of the plant nutrients have their max availability. Color illustrations are given of the symptoms of plant deficiencies and toxicities.

White mold, caused by the fungus Sclerotinia (Whetzelinia) sclerotiorum, is distributed worldwide and has more than 300 hosts. It infects flowers, cotyledons, seeds, leaves or injured plant tissue. The disease can be controlled by crop rotation, flooding, reduced seeding rates, application of chemical products in the middle of the flowering period, modifying plant architecture and the use of resistant var. Many soil microorganisms are associated with sclerotia and may cause them to degrade or fan to germinate. The symptoms and damage caused by the disease are illustrated in color.

En ensayos de campo efectuados en 1977-79 en CIAT-Quilichao, se establecieron al finalizar 1977, a) 5 especies de gramineas altas y espesas, b) 6 especies de gramineas estolonifgeras semi-erectas, c) 6 especies de gramineas de escasa doiseminacion, d) 6 especies de leguminosas rastreras, e) 6 especies de leguminosas arbustivas y f) 6 especies de leguminosas forrajeras; se aplico 0 o 100 kg de N + 44 kg de P2O5 + 100Kg de cal o 200 kg de N + 88 kg de P2O5 +41 kg de K2O + 2t de cal/ha.

En 1977 se inicio la evaluacion de los recursos de tierra para estudiar las regiones de Oxisoles y Ultisoles en America del Sur, con el objeto de ayudar a establecer prioridades tecnicas para el mejoramiento de la tierra. Esta parte del trabajo se completo en 1979, pero el estudio ha sido ampliado para proporcionar informacion sobre otros cultivos de la region Andina, y sobre la produccion de cultivos, agroforestal y de forrajes en America Latina.

Se detallan evaluaciones de campo e invernadero en las que se examinaron: el efecto de diferentes rocas fosforicas (RF), la eficacia de la aplicacion de P, el tamano de los granulos y las relaciones RF: Superfosfato triple, asi como los efectos de las mezclas cogranuladas de RF con superfosfato triple y superfosfato simple, y la RF parcialmente acidulada, en varias especies, incluyendo Brachiaria decumbens, Zea mays y Panicum maximum. (Herbage Abstracts-CIAT)

Different nutritional deficiencies or toxicities may limit bean development and yield. N and P deficiencies are the most frequent, although deficiency of minor elements and Al/Mn toxicity can reduce yields considerably. Nutritional problems are usually diagnosed by soil and plant tissue analyses and the observation of symptoms produced by nutritional disorders. Optimum pH for bean production varies between 6.5-7.5; within these limits, the majority of the plant nutrients have their max availability. Color illustrations are given of the symptoms of plant deficiencies and toxicities.

Efforts to develop cassava technology for the vast areas of acid infertile soils were continued Large-scale germplasm screening in the field was begun in Carimagua for tolerance to low levels of P and acidity and in Quilichao, for tolerance to low levels of P. Various fertilizer trials were used to determine: (a) nutrient absorption and distribution within the plant during a 12-mo.

Research of the physiology section was centered on identifying the characters associated with high root yields and quality in cassava under stress conditions. Plant reaction to water stress was studied, specifically regarding growth and yields of var. M Mex 59 and M Col 22 with a period of artificial rain exclusion. Observations were made throughout the stress period and subsequent recovery. Water stress reduced LAI notably although M Mex 59 maintained a LAI approx. twice that of M Col 22 during the stress period. LAI for both var.

Research of the physiology section was centered on identifying the characters associated with high root yields and quality in cassava under stress conditions. Plant reaction to water stress was studied, specifically regarding growth and yields of var. M Mex 59 and M Col 22 with a period of artificial rain exclusion. Observations were made throughout the stress period and subsequent recovery. Water stress reduced LAI notably although M Mex 59 maintained a LAI approx. twice that of M Col 22 during the stress period. LAI for both var.

Efforts to develop cassava technology for the vast areas of acid infertile soils were continued Large-scale germplasm screening in the field was begun in Carimagua for tolerance to low levels of P and acidity and in Quilichao, for tolerance to low levels of P. Various fertilizer trials were used to determine: (a) nutrient absorption and distribution within the plant during a 12-mo.