Photosynthetic potential and productivity of annual mixed crops in Northern Kazakhstan.
One of the serious shortcomings in modern forage production in Kazakhstan is the low nutritional value of forage. Cultivation of mixed crops of annual traditional forage crops with new high-protein annual forage crops Echinochloa frumentacea L. and Pennisetum glaucum (L.) R. Br. will help solve this problem. Mixtures are chosen to obtain high yields and feed quality; however, the photosynthetic and other properties of such mixtures are not well understood. This research evaluated the productivity and photosynthetic activity of annual grass mixtures over three growing seasons. Sorghum var. eusorghum Pers., Echinochloa frumentacea L, and Pennisetum glaucum (L.) R. Br. were grown as pure crops and in mixtures with Hordeum vulgare L. + Sorghum var. eusorghum Pers. + Sorghum sudanense hybrid P. + Pisum sativum L. Simultaneously, highly productive crops - Echinochloa frumentacea L. and Pennisetum glaucum (L.) R. Br., are newly introduced crops for the north of Kazakhstan. It was analyzed feed yield, quality, gas exchange, and chlorophyll fluorescence parameters. Mixed crops of annual forage crops improved forage yield, root-to-aerial ratio, and crude protein and lignin content. The results showed that the crops in the mixtures had higher net photosynthesis, water consumption, high water use efficiency, and nitrogen content in leaves (N) but a lower carbon ratio. Pennisetum glaucum (L.) R. Br. had a lower light compensation point and dark respiration rate, suggesting good shade tolerance. However, water scarcity reduced the biomass and photosynthetic capacity of Pennisetum glaucum (L.) R. Br. and the herbal mixture with its inclusion, respectively. Also, Pennisetum glaucum (L.) R. Br. was sensitive to soil moisture. The mixture with Echinochloa frumentacea L. had higher biomass and water use efficiency. Echinochloa frumentacea L. had a higher light saturation point in the mixture, indicating high light utilization efficiency. Based on the results, we could conclude that mixed crops improved feed production and photosynthetic capacity. The research provides a scientific basis for the creation of forage mixtures with high yields and quality.